bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Annealing on Mechanical Properties of Copper Alloys Deformed at Cryogenic Temperature
Authors: Wu Xiao Xiang , Gong Yu Lan , Ren Shi Ying , Tao Jing Mei , Long Yan , Cheng Lian Ping , Zhu Xin Kun
Published: March 2013

The effect of annealing treatment on the mechanical properties and microstructure of cold-rolled Cu-20% Zn alloys was investigated in this work. Mechanical properties changed dramatically with the increase of temperature. According to the microhardness test, it can roughly concluded that 150 is the optimal annealing temperature for deformation, at which a uniform elongation increased from 1.4658% before annealing to about 6.89%, and the elongation to failure increased from 7.426% to 16.81% with the same strength almost retained. The changes of microstructure during the annealing process are mainly distributed to the improvement of mechanical properties.
Improvement of the Hydrophilicity of Cu/LDPE Composite and its Influence on the Release of Cupric Ions
Authors: Tang Ying , Xia Xian Ping
Published: March 2013

t is of great importance to improve the hydrophilicity of Cu/LDPE composite, a material for a new type of IUDs (Intrauterine Devices). The aim of the study is not only satisfying the biocompatibility of medical devices implanted in human bodies, but also improving the releasing rate of cupric ions. In this study, various hydrophilic materials (sodium chloride, anhydrous glucose and soluble starch) were added respectively, in order to improve the hydrophilicity of Cu/LDPE composite. The microstructure of Cu/LDPE composite was characterized, moreover, the influence of the addition of these hydrophilic materials on the surface hydrophilicity and the releasing rate of cupric ions of Cu/LDPE composite was studied. The compatibility between three hydrophilic materials and the matrix of LDPE is rather different, which can affect the dispersible uniformity of these additives in Cu/LDPE composite, and the dispersible uniformity of NaCl is the worst among these three hydrophilic materials. The addition of three hydrophilic materials was all beneficial to the improvement of the hydrophilicity of Cu/LDPE composite. Connected holes were formed in Cu/LDPE composite, which provided channels for the infiltration of solution and the diffusion of cupric ions, and improved the releasing rate of cupric ions in the Cu/LDPE composite IUDs.
Study on the Sintering Mechanism of Tin Oxide Ceramics Doping with Pr2O3
Authors: Wang Qing Wei , Wang Hong Zhi , Ning Wei , Luo Li Da
Published: March 2013

The Pr2O3 doped SnO2 dense ceramic was prepared by co-precipitation method and further sintering. Through the micrograph of the cross-sectional microstructure of the electrodes, the sintering process was analyzed and discussed. Results showed that the solid phase sintering was exhibited at the early stage; when sintering was kept going on, the instant liquid phase could be emerged due to the rich dopants in the grain boundary. Finally, there would be much secondary phase existe as the concentration of dopants reached to a certain value.
Effects of SiO2 and ZrO2 Additives on Microstructure and Properties of Al2O3 Ceramic
Authors: Li Yi Hua , Jia De Chang , Yang Zhi Hua , Zhou Yu
Published: March 2013

Alumina ceramic, with high mechanical strength, good electric insulation, high hardness and good corrosion resistance performance, has been widely used in machinery, electronic and electrical, chemical, medicine, construction and other high-tech areas. In this study, both silicon sol and zirconia particles are incorporated into the system and dense alumina composite ceramics were prepared by cold isostatic processing and pressureless sintering at 1550 . The influence of additives on phase composition, microstructure and mechanical properties were investigated. The XRD results show that mullite phase was generated in the composite ceramic. The composite ceramic has excellent comprehensive performance. For example, the sample with 3wt.% SiO2 and 5wt.% ZrO2 has density of 3.87g·cm-3, Vickers hardness of 17.6GPa, flexural strength of 369.0MPa, youngs modulus of 374.2GPa and fracture toughness of 3.57MPa·m1/2.
Tensile Strength and Bonding Mechanism of the Mullite Eramic/Ceramic Sample Joined by Phosphate Adhesive
Authors: Hao Rui Hua , Liu Jia Chen , Wang Min , Dong Xue , Wang Ming Chao
Published: March 2013

The aluminum phosphate adhesive was prepared by aluminum dihydrogen phosphate and ceramic fillers. The mullite, silica and silicon powders were added as the fillers to improve the mechanical property and high temperature property. The specimens were prepared by joining the mullite ceramic/ceramic by phosphate adhesive. The strengths of the specimens treated at different temperatures were studied. The results indicated that the tensile strength at room temperature was 2.02 MPa, and it reached 5.06 MPa when the specimen was treated at 800°C. The bonding effect and bonding property at high temperature were discussed through the SEM analysis. Besides, the bonding mechanism was also explored.
Study on the SiC-Al Co-Continuous Phase Composites
Authors: Jiang Guo Jian , Ding Liu Liu , Liu Yun Ying , Xiong Wei , Ni Yang Sheng , Yao Xiu Min , Xu Jia Yue , Li Wen Jun
Published: March 2013

SiC/Al co-continuous phase composites were fabricated by pressureless infiltration technology with reticulated silicon carbide porous ceramics as matrix and aluminum or magnesium as reinforcement phase. The effect of magnesium addition and holding time on the relative density, mechanical properties and macro morphology of the composites was investigated. The results showed that the porosity of SiC/Al co-continuous phase composites decreased with the increase of the holding time. The wettability of SiC and Al was improved with the addition of Mg. The hardness of SiC/Al co-continuous phase composites increased with the increase of the holding time. SiC and Al combined closely at longer holding time.
Sintering Performance of MgAl2O4 Spinel with Various Al2O3 Content
Authors: Zhang Wei , Shi Gan , Feng Zhi Yuan
Published: March 2013

Magnesium aluminate spinel specimens with various Al2O3 content were prepared. Sintering performance and microstructure of different kinds of MgAl2O4 spinel were studied. It is found that the sintering of materials becomes more difficult with the increase in their Al2O3 contents. Corundum begins to precipitate from the magnesium aluminate spinel with 85wt% Al2O3 at 1400. However, with further increase in the sintering temperature, the corundum dissolves into magnesium aluminate spinel (above 1600). The precipitation and solid solution of corundum hinder the sintering of materials. In alumina-rich spinel, if the content of Al2O3 in alumina-rich spinel materials is more and the content of CA6 is also more. At the same time CA6 crystal is bigger in the alumina-rich spinel.
Catalytic Properties of ZrB2-Based Ultra-High Temperature Ceramics Based on the Wall Temperature Response Method
Authors: Li Ning , Hu Ping , Zhang Xing Hong , Han Wen Bo
Published: March 2013

This paper presented the application of microwave-discharge plasma apparatus which was used to evaluate the catalytic properties of ZrB2-based ultra-high temperature ceramics in the simulated real service environment by the wall temperature response method based on the heat balance principle. The results showed that the material composition had a significant influence on the catalytic properties of ZrB2-based ultra-high temperature ceramics, and the catalytic activity of ZrB2-SiC composites with Cr addition had been increased significantly. The relationship between catalytic properties of ZrB2-based ultra-high temperature ceramics and surface composition was discussed in detail. The composition optimization was considered to be a very effective way to inhibit the recombination reactions of dissociated atoms on the surface of ultra-high temperature ceramics.
In Situ Synthesis of SiC and β-Si3Al3O3N5 Whiskers in Alumina Carbon Based Materials
Authors: Li Xiang Cheng , Zhu Bo Quan , Zhao Fei
Published: March 2013

SiC whiskers are the common reinforced phases in alumina carbon refractories. In this paper, the effect of transition metal catalyst on the evolution of matrix phase and the formation of β-Si3Al3O3N5 whiskers were studied. It was found that the whiskers of both SiC and β-Si3Al3O3N5 in alumina carbon materials with the catalyst in reducing atmosphere were generated. The existence of catalyst can promote the nitriding process of Si metal and facilitate the formation of β-Si3Al3O3N5 whiskers. The growth mechanism of both SiC and β-Si3Al3O3N5 whiskers agrees with the vapor-liquid-solid model.
Microstructure and Electrochemical Performances of AlxFeCoNiCr(B) High Entropy Alloys
Authors: Zhu Sheng , Du Wen Bo , Wang Xiao Ming , Han Guo Feng
Published: March 2013

High entropy alloys are new alloys composed of over five principal elements with each having an atomic percentage in the range of 5%~35%, which break through the concept of traditional alloys design. In this paper, AlxFeCoNiCr (B) high entropy alloys were prepared in an vacuum arc induction melting furnace. The microstructure presents simple solid solution structure, and the fraction of FCC crystal structure decreased with increasing of Al content. Chromium tends to segregate at the inter-dendrite grain boundary. Electrochemical investigations indicated that AlxFeCoNiCr (B) high entropy alloys were more corrosion resistance than 316L stainless steel.
Microstructure and Properties of Multi-Component AlxCoCrFeNiTi0.5 High-Entropy Alloys
Authors: Dong Yong , Lu Yi Ping , Zhang Jun Jia , Li Ting Ju
Published: March 2013

The multi-component AlxCoCrFeNiTi0.5 (x=0, 0.2, 0.5, 0.8, 1.0) high-entropy alloys were prepared by vacuum arc melting. The microstructure and mechanical properties were studied. It was found that the structure transformed from FCC into FCC + BCC + Laves, and finally into BCC with the increase of Al content. The compress test results showed that with the addition of aluminium from 0 to 1.0, the fraction strength increased while plasticity reduced. In the stain rates of 5×10-3/s and 1×10-3/s, when x=0.8 the fraction strength achieved maximum and x=0 the plastic was best, the strength of 2879MPa and 2433MPa, the strain of 0.21 and 0.22, respectively. The hardness increased obviously (from Hv479.1 to Hv692.7) when Bcc phase and Laves phase appeared. The analysis revealed that the strengthen mechanism was mainly composed of solid solution strengthening and precipitation strengthening.
Preparation of TiAl Intermetallic Alloy by Gelcasting
Authors: Ye Qing , Guo Zhi Meng , Duan Qi Kai , Yang Chun Lei , Hao Jun Jie
Published: March 2013

TiAl intermetallic alloy was prepared by gelcasting. The alloy powders were synthesized through reaction diffusion. The microstructure was investigated by XRD and SEM. The results showed that titanium aluminide powders were synthesized from elemental powders under the condition of 600°C for 3h. The solid loading of metal slurry was 45%. After gelcasting, drying and sintering at 1480°C for 2h, TiAl with the relative density of 93% was successfully prepared.
Influence of Exposure at 750°C on Room Temperature Tensile Ductility of Cast TiAl Alloy with the Directional Lamellar Microstructure
Authors: Zhu Chun Lei , Zhang Xi Wen , Zhang Ji
Published: March 2013

In this study, based on cast Ti-47.5Al-2.5V-1.0Cr (at. %) alloy with the directional lamellar microstructure, the influence of exposure at 750 in air on room temperature tensile ductility was investigated as a function of time, ranging from1hr to 300hr, in order to determine the onset exposure time for a significant reduction in RT ductility and the fracture mechanism for the exposed specimens. The results indicated that this alloy could still retain more than 2.0% of its ductility after exposure at 750 for 150hr, and its ductility decreased to 1.58% and ~1.0% even after exposure for 200hr and 300hr, respectively. High ductility for the directional lamellar microstructure could be retained after exposure for 150hr, which was attributed to its high crack origination and propagation resistance at specific lamellar orientation. And the fracture mechanism of the exposed specimen with this special structure would also be discussed.
Investigation on B, Cr Doped Ni3Al Alloy Prepared by Self-Propagation High-Temperature Synthesis and Hot Extrusion
Authors: Sheng Li Yuan , Guo Jian Ting , Yuan Chao , Yang F. , Li G.S. , Xi T.F.
Published: March 2013

The Ni3Al and Ni3Al-B-Cr alloys were fabricated by the self-propagation high-temperature synthesis with hot extrusion method. Their microstructure and mechanical properties were studied by using combination of X-ray diffraction, optical microscopy, transmission electron microscopy and compression test. Analysis of X-ray spectra exhibited that the elemental powders had been transformed to the Ni3Al phase after the self-propagation high-temperature synthesis processing. Microstructure examination showed that the alloy without extrusion consisted of coarse and fine grains, but the subsequent hot extrusion procedure homogenized the grain size and densified the alloy obviously. Transmission electron microscopy observations on the Ni3Al alloy revealed that Ni3Al, γ-Ni and Al2O3 particles were the main phases. When the boron and chromium were added, besides the β-NiAl phase, α-Cr phase and some Cr7Ni3 particles with stacking faults inside were observed. In addition, a lot of substructure and high-density dislocation arrays were observed in the extruded part, which indicated that the subsequent extrusion had led to great deformation and partly recrystallizing in the alloy. Moreover, the subsequent extrusion procedure redistributed the Al2O3 particles and eliminated the γ-Ni. These changes were helpful to refine the microstructure and weaken the misorientation. The mechanical test showed that the self-propagation high-temperature synthesis with hot extrusion improved the mechanical properties of the Ni3Al alloy significantly. The addition of B and Cr in Ni3Al alloy increased the mechanical properties further, but the compressive strength of the alloy was still lower than that synthesized by combustion. Finally, the self-propagation high-temperature synthesis with hot extrusion was a good method to prepare Ni3Al alloy from powder.
A Study of Laser Cladding on the NiCr/Cr3C2-WS2-CaF2 Coating
Authors: Chen Shu Fa , Feng Cheng Long , Yang Jin , Chen Jin Song
Published: March 2013

NiCr/Cr3C2-WS2-CaF2 mixed powders were prepared on 1Cr18Ni9Ti stainless steel substrate to fabricate high-temperature self-lubrication wear resistant composite coating by laser cladding. The microstructure of the coating was examined by means of XRD, SEM and EDS. The high-temperature dry sliding friction and wear behavior of the composite coating were evaluated by using a ball-on-block wear tester at room temperature, 300 and 600 , respectively. The results showed that the composite coating had a unique microstructure consisting of γ-(Ni,Fe) solid solution matrix, Cr7C3/WC reinforcement and CrS/WS2 lubricant particles. The hardness of NiCr/Cr3C2-WS2-CaF2 coating by laser cladding was lower than NiCr/Cr3C2 coating, but higher than stainless steel substrate significantly. It was because of the addition of solid lubricant. In the wear process, elevated temperature was helpful to form a lubricating transfer film. As a result, the NiCr/Cr3C2-WS2-CaF2 coating exhibited a notable anti-friction and wear resistance at 300 and 600 .
Manufacturing Technology of Magnesium Alloy Bicycle Parts
Authors: Shi Zi Mu , Niu Li Yuan , Lin Ji Xing , Sun Da Ren , Li Yong , Zhao Lan , Li Guang Yu
Published: March 2013

One kind of deformed magnesium alloy with high strength and high plasticity was made to be bicycle parts. Meantime, the microstructure and mechanical properties of the magnesium alloy were analyzed. In addition, the deformation and welding technology of taper pipe and shaped tube of bicycle were studied. The results showed that the bicycle parts manufactured through extruding and welding of the new type magnesium alloy have high strength, good plasticity. The tensile strength can reach 321.3 MPa and the elongation is more than 20%. By adopting the new welding process of internal mending and cuttage grafting, the after-welding-strength is 90.2%. of the base metal Meanwhile, the industrialization level can meet the requirements of European Union (EU) vehicle standards.
Effect of Zn Addition on Microstructure and Mechanical Properties after Extrusion, Rolling and Ageing in Mg-9Gd-3Y-0.5Zr Alloys
Authors: Tang Wei Neng , Li S.Q. , Chen Rongshi , Han En-Hou , Ke Wei
Published: March 2013

Evolution of microstructure and mechanical properties of the Mg-9Gd-3Y-0.5Zr base alloys without 0.5% Zn addition (GWK930) and with Zn addition (GWZK9300) have been investigated during processing by extrusion, rolling and ageing. It was found that the yield/ultimate strength of the two as-rolled alloys increased with the rolling strains. Twinning was the main deformation mechanism in GWK930 alloy while few twinning could be detected in the GWZK9300 alloy due to the dense secondary phases such as LPSO structure. The (0002) texture intensity in two as-rolled alloys increased with the rolling reduction, however, a typical rolling basal plane texture with single peak was found in GWZK9300 while a bimodal texture was found in the GWK930 alloy. Compared with GWK930 alloy, GWZK9300 alloy exhibited higher strength and ductility after rolling, annealing and ageing treatments. The finer grain size was due to more recrystallization fraction, while more fine secondary phases dispersed in matrix. And the basal texture strengthening after rolling deformation and subsequent heat treatment are suggested to be responsible for the superior comprehensive mechanical properties of GWZK9300 alloy.
Formation of a New Mg-Cu-Ni-Gd Bulk Metallic Glass: Effects of Rare Earth on Glass-Forming Ability of Mg-Tm-Re Bulk Metallic Glasses
Authors: Yin Jian , Zhou Zhi Jian , Qi Zhi Peng , Liu Yi
Published: March 2013

A new Mg65Cu18Ni6Gd11 bulk metallic glass (BMG) with high level of Ni content, exhibiting glass-forming ability (GFA) of 6 mm, was fabricated by copper mold casting. The compressive strength and plasticity of the Mg65Cu18Ni6Gd11 BMG were 938 MPa and 0.14%, respectively. The composition design of the Mg65Cu18Ni6Gd11 BMG with enhanced GFA had succeeded simply using Gd substituting Y in the Mg65Cu18Ni6Y11 BMG, which was a result of a comparison on the GFA between the Mg-TM-Gd and Mg-TM-Y BMGs (TM: transition metals). Compared to the Mg-TM-Y BMGs, the Mg-TM-Gd BMGs exhibited improved GFA, which was demonstrated to be mainly attributed to the more negative amorphous formation enthalpy resulting from Gd substituting Y. The effects of rare earth (RE) elements on the GFA of Mg-TM-RE were discussed. This work may suggest an easy way for developing new Mg-based BMGs with improved GFA by rare earth (RE) design.
Effects of Gd on the Microstructure and Mechanical Properties of Mg-3Sn Alloys
Authors: Luo Jun , Chen Rongshi , Han En-Hou
Published: March 2013

The microstructure and mechanical properties of as-cast Mg-3Sn-xGd (x=0, 0.2, 1 wt.%) alloys were studied by using OM, SEM, EDX, XRD etc. With the increase of Gd, the formation of Mg2Sn phase was impeded and the MgSnGd phase formed and the volume fraction of this new phase obviously increased. The ultimate tensile strength and elongation to failure increased with dilute Gd addition but sharply decreased when the Gd addition comes to 1.34 wt.%. The possible reasons for the variation in microstructure and mechanical properties were discussed.
In Vitro and In Vivo Studies on a MgLi-X Alloy System Developed as a New Kind of Biological Metal
Authors: Luo Sha , Zhang Qing Qing , Zhang Yan Chang , Li Chao , Xu Xiao Qing , Zhou Tie Tao
Published: March 2013

Magnesium alloys have a good application prospect in the fields of bone implants and cardiovascular stents due to their excellent properties, such as close density and elastic modulus to those of nature bone, high specific strength and rigidity, biodegradation and biocompatibility. In this paper, the feasibility of the use of the forged Mg-Li-X alloys (Mg-Li-Al-Zn-Ca-Sr) as biodegradable metals was investigated by immersion tests in the Hanks solution and skin-tissue implantation tests. The methods of SEM-EDS and XRD were used to research the corrosion morphology and corrosion products of the forged Mg-Li-X alloys after the in-vitro and in-vivo tests. At last, the in-vitro cytotoxicity was investigated by the MTT tests on L929 cells. Results showed that corrosion mechanism of the forged Mg-Li alloys was pitting and the surfaces were covered by Mg (OH)2,CaCO3 and Ca (H2PO4)2 . During the 5 weeks implantation period, the rats survived from the operation, which indicates that the elements and the compounds formed are non-toxic to the rats. The forged Mg-Li alloy showed Grade 0~1 cytotoxicity, which manifests the forged Mg-Li alloy has good biocompatibility and eligible toxicity for implant applications.
Effect of Processing Speed on Microstructures and Mechanical Properties of Submerged Friction Stir Processed AZ91 Alloy
Authors: Chai Fang , Zhang Da Tong , Zhang Wen , Qiu Cheng
Published: March 2013

Normal and submerged friction stir processing (SFSP) were conducted to AZ91 magnesium alloy plates with 6mm in thickness, and influence of processing speed (ν) on microstructures and mechanical properties of the experimental materials was investigated. The results revealed that fine and equiaxed grains were observed in the stirred zone (SZ). As the processing speed increased from 60mm/min to 150mm/min, the average grain size in the SZ of normal FSP material decreased. However, the grain size of the SFSP specimens first increased with the processing rate increasing from 60mm/min to 120mm/min, and then decreased when the processing rate increased to 150mm/min. Microstructure of the SFSP specimen was much finer compared with the normal FSP one, and the grain size of α-Mg was about 1.2µm when the processing speed was 60mm/min during SFSP. Because of much finer microstructure of SFSP, the microhardness, tensile strength and elongation were all improved. SEM fracture observation showed that fine dimples and tearing edges could be observed on SFSP specimen which showing good ductility. In addition, high temperature tensile tests showed that SFSP AZ91 alloys exhibited excellent superplasticity at high strain rate, with an elongation of 1202% at 623 K with a strain rate of 3x10-3s-1. The present study demonstrated that SFSP possesses great potential in preparing fine-grained materials.
Microstructure and Mechanical Properties of Mg-6Zn-2Si Alloy Processed by Equal Channel Angular Pressing
Authors: Zhang Yi , Han Fu Yin , Wang Yong Sheng , Liang Wei , Wang Ping , You Jia Xue , Zhong Xi Ting
Published: March 2013

The Mg-6Zn-2Si alloy was processed by equal channel angular pressing (ECAP) for 4 passes and 8 passes at 573K, and the microstructure and mechanical properties of the alloy before and after ECAP were studied. The results show that Chinese script type interphase of Mg2Si was crushed into dispersed particles, and significant grain refinement was also introduced to the matrix phase (α-Mg) and Mg51Zn20 phase after 4 passes of ECAP. The yield strength was increased by 180%, elongation by 140% and tensile strength by 75%. The microstructure and mechanical properties remained reasonably constant between 4 and 8 passes of ECAP. The mechanism of improvement on microstructure and mechanical properties of the experimental alloy by subjecting ECAP was also investigated.
Optimization of Heat Treatment Process on Vacuum Die-Casting AT72 Magnesium Alloy
Authors: Li Da Quan , Liu Yong , Xu Jun , Shao Shuang , Xu Chun Shui , Lu Xian Feng , Yang Xiang Jie
Published: March 2013

The effect of heat treatment on vacuum die-casting (VDC) AT72 magnesium alloy was studied. The optimal process of heat treatment was obtained. The result shows that the alloy was composed of α-Mg, Mg17Al12 and Mg2Sn. After solution treatment at 686K for 24h, Mg17Al12 completely dissolved in α-Mg matrix. With the aging treatment following solution treatment, Mg17Al12 kept precipitating in the matrix and along grain boundary. Moreover, Mg2Sn distributed along the grain boundary did not disappear after solution treatment at 686K. This indicates that Mg2Sn phase exhibits very high thermal stability. The heat treatment process was optimized with solution at 686K for 24h plus ageing at 473K for 18h, in the condition of which AT72 magnesium alloy exhibits a maximum hardness with value of 90.8Hv. The successful application of heat treatment for AT72 magnesium alloy could be attributed to the elimination of the air bubble in the casing through VDC. However, the porosity in the cast couldnt be efficiently eliminated by VDC, which result in the growth of shrinkage pore.
Study on Interface Characteristics of Al/Mg/Al Composite Plates Fabricated by Two-Pass Hot Rolling
Authors: Luo Chang Zeng , Liang Wei , Li Xian Rong , Yao Ya Jun
Published: March 2013

In this study, 5052/AZ31B/5052 composite plates were fabricated by two-pass hot rolling, under the rolling parameters 623 K/15 min/40% for the first pass and 673 K/10 min/50% for the second pass. The structure and element change in the zone of the joint interface were studied by means of optical microscope (OM), scanning electron microscope (SEM), and energy diffraction spectrum (EDS). The results showed that the bonding mode of the joint interface between AZ31B and 5052 alloy was metallic bonding after the first pass hot rolling, but the bonding mode of the finished composite plate appeared the distribution characteristic alternating with metallic bonding and metallurgical bonding. Two distinct intermediate layers including Mg17Al12 and Al3Mg2 can be clearly observed in the joint interface. During the second pass hot rolling, the AZ31B and 5052 layer were elongated along the rolling direction, while the Al3Mg2 and Mg17Al12 layers were up in the joint interface. After the tensile strength testing of the composite plate, the interface bonding appeared very well without any debonding.
Influence of Annealing Temperature on Microstructure and Properties of Warm-Rolled AZ31 Magnesium Alloy Sheets
Authors: Zhang Hua , Huang Guang Sheng , Lin Jin Han , Wang Li Fei
Published: March 2013

Warm-rolled AZ31 alloy sheets were annealed at different temperatures ranging from 150 to 450°C. Effects of annealing temperature on microstructure and properties of warm-rolled AZ31 alloy sheets, especially the formability, were investigated. The results revealed that the Lankford value (r-value) and strain-hardening exponent (n-value) first increased and then became relatively steady with the increase of annealing temperature. The Erichsen value (IE) first increased and then decreased with the increase of annealing temperature and the AZ31 alloy sheets exhibited the highest IE of 3.02 mm when annealing at 250°C, which can be mainly attributed to a larger elongation, a lower r-value and a higher n-value.
Effect of Al2Ca Compound on Microstructure of As-Cast AZ31 and AZ61 Alloys
Authors: Yang Qing Shan , Jiang Bin , Huang Xiao Yong , Li Xiao Ke , Pan Fu Sheng
Published: March 2013

The inoculation effect of Al2Ca intermetallic compound on microstructure evolution was examined performed on as-cast AZ31 and AZ61 alloys. The refinement mechanism of Mg-Al alloys was discussed with the Miedema model and edge-to-edge matching model. Al2Ca compound has a good crystallographic matching relation with Mg matrix, which formed in the solidification process. It is considered that Al2Ca can act as a potential and effective heterogeneous nucleation center. The results reveal that the grain refinement effect of Al2Ca compound has more pronounced in AZ31 alloy compared with in AZ61 alloy.
Effects of Shrinkage Porosity on Mechanical Properties of a Sand Cast Mg-Y-Re (WE54) Alloy
Authors: Li Ji Lin , Ma Yue Qun , Chen Rongshi , Ke Wei
Published: March 2013

The distribution of shrinkage porosities in sand cast Mg-Y-RE (WE54) alloy castings was characterized through density measurement and calculated by Archimedess principle. The effect of porosity on mechanical properties of sand cast WE54 alloy was investigated through tensile tests and microstructure observation. It was found that the shrinkage porosities distributed mainly in the middle of the plate where the liquid feeding was quite inconvenient. And the porosities were formed along grain boundaries when secondary phases formed at the end of solidification. Hardness tests showed that the vikers hardness declined linearly with increasing porosity volume fraction. While the tensile strength and nominal yield strength declined exponentially as the porosity volume fraction increased. Microstructure observation showed that the fracture cracks propagated along the grain boundaries where porosities and secondary phases gathering together in as-cast WE54 alloy. The tiny porosities distributed in the secondary phases were observed, which could reduce the tensile strength of cast specimens significantly. The heat treatment strengthening effects were significantly weakened by porosities, and even no heat treatment strengthening effect was detected when the porosity volume fraction was higher than 1%. The microstructure observation also proved that no heat treatment strengthening effect existed in samples containing porosities.
Microstructure and Tensile Properties of Mg-4Zn-2Sn-2Al Alloy
Authors: Zhao Dong Qing , Dong Xu Guang , Zhang Xin En , Gao An Jiang , Zhou Ji Xue , Yang Yuan Sheng
Published: March 2013

The microstructures and tensile properties of as-cast, solution-treated and aged Mg-4Zn-2Sn-2Al (wt.%) alloy have been investigated. The microstructure of the as-cast alloy consists of α-Mg, Mg2Sn and Mg32(Al,Zn)49 phases. The yield tensile strength and the ultimate tensile strength of the as-cast alloy are 87.7 MPa and 241.3 MPa, respectively, and the elongation reaches to 18.8% showing excellent ductility. After solution treatment, all of the Mg32(Al,Zn)49 phase and the majority of Mg2Sn particles have dissolved into the matrix. During aging process, Mg2Sn phase precipitates from the α-Mg supersaturated solid solution. With the precipitation strengthening of Mg2Sn phase, the yield tensile strength and the ultimate tensile strength of the alloy increase to 112.5 MPa and 280.4 MPa, respectively, while, the elongation decreases to 12%.
Numerical Simulation Research on Wide Casting Nozzle of Twin-Roll Magnesium Alloy
Authors: Liang Xiao Ping , Liao Sang Sang , Xiao Lei , Jiang Bin
Published: March 2013

Casting nozzle structure is the decision factor for the formation process of the fluid field of magnesium alloys melt, and the distribution uniformity of the casting nozzle has an important influence on the process stability and the billet quality. In this research, the casting nozzle structures used in producing AZ31 magnesium alloys slab with width of 1500 mm by using horizontal twin-roll continuous casting were taken as research object, and the fluid field of magnesium alloy melt in different casting nozzle structures were simulated, and the influences of the numbers, position, shape and size of the divergent fluid block on the fluid velocity were analyzed. The results show that the fluid velocity distribution obtained by seven divergent fluid blocks were superior to five or three divergent fluid blocks, the streamline divergent fluid blocks were superior to the linear ones, and the small divergent fluid blocks were superior to big ones. At the same time, a new casting nozzle structure was presented, the difference between the maximum and minimum fluid velocity by using the new casting nozzle was 4.69%, and the distribution uniformity of fluid velocity meets the requirement of production.
Temperature Field and Cast-Rolling Force Prediction during Horizontal Twin-Roll Casting Magnesium Alloy
Authors: Liang Xiao Ping , Xiao Lei , Liao Sang Sang , Jiang Bin
Published: March 2013

The control of process parameters in the horizontal twin-roll casting is crucial for the quality of sheet and the continuity of the process. A temperature field coupled with flow field mathematical model was established during the horizontal twin-roll casting of AZ31 magnesium alloy sheet with 1500mm in width and 8mm in thickness in this paper. The temperature field in the casting zone was solved by the software ANSYS. The effect of process factors, such as casting speed, pouring temperature and cooling intensity, on casting zone temperature of different process parameters were studied. Based on the solved temperature field, with the hot roll formula and test data of yield strength, the effect of casting speed, pouring temperature and cooling intensity on cast-rolling force in the cast-rolling zone was also dicussed. The results indicate that the casting speed has the greatest effect upon the temperature field and cast-rolling force, while the pouring temperature is the least. In addition, the value of critical cooling intensity increased with the increase of the casting speed. The quality defect called melt sheet or the leakage phenomenon appear when the cooling intensity is lower than the minimal critical cooling intensity value, and crack or rolling suspended appear if the cooling intensity is higher than the maximal critical cooling intensity value. When the casting speed are 1m/min, 2m/min and 3m/min, the minimal and maximal critical cooling intensity are 500, 1200, 2 000 W/(m2.K) and 2500, 5000, 7500 W/(m2.K) respectively.
Microstructure and Kinetics of β-Mg17Al12 Phase Transformation for Warm Rolled AZ91 Magnesium Alloy
Authors: Yang Lin , Wang Jun Dong , Wang Si Ni , Lin Li , Liu Zheng
Published: March 2013

The microstructure and the kinetics of β-Mg17Al12 phase transformation during annealing process for warm-rolled AZ91 magnesium alloy were investigated. The results showed that few twins were found in solid state AZ91 magnesium alloy after warm rolling, which provides energy for β-Mg17Al12 particles to nucleate and growth; the β-Mg17Al12 particles were prior to form at α-Mg, twin grains boundary and especially the place of high energy; by the annealing time extending, the quantity of β-Mg17Al12 particles increased. And combined with the experimental data and the JMAK equation, the fitting equation of Kinetics of β-Mg17Al12 phase transformation was built. During annealing process, the twin grains disappeared and the original bulky organization was replaced by recrystallization grain, while the grain refinement was obvious with the grain reduction to 20-60μm.
Metal Flow Behaviour in Tee Joint Valve Body Multidirectional Extrusion
Authors: Cheng Mei , Zhang Zhi Min
Published: March 2013

By multi-axis active load deformation method, the equivalence diameter tee joint was formed on multi-axis numerical control hydraulic press machine. The loading route was determined by numerical simulation. The experiment results showed that two loading method can complete form the parts. The different directions metal flow was observed under multi-axis loading conditions. To simplify analysis, the flow field was divided into several regions. In every region, the metal flow direction was only one. In multi-axis loading, the way of deformation follows priority deformation principle: The metal flows only choose one direction even if the work piece were under the complicated coupling field condition. The mathematical model of the deformation force and metal flow rate was established. The theoretical calculation had been provided.
Corrosion and Electrochemical Behaviors of As-Cast Mg-8Y and Mg-5Y-7Gd-1Nd-0.5Zr Magnesium Alloys in NaCl Aqueous Solution
Authors: Zhang Xin , Deng Xia , Zhang Kui , Li Xing Gang , Shi Yang , Zhang Yu Long , Peng Min , Kong Ling Ying
Published: March 2013

The corrosion mechanisms of as-cast Mg-8Y and Mg-5Y-7Gd-1Nd-0.5Zr Mg alloys in 5% NaCl aqueous solution were investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion resistance of Mg-8Y and Mg-5Y-7Gd-1Nd-0.5Zr alloys in 5% NaCl aqueous solution gradually deteriorated with increasing of immersion time expect for 2h and 24h immersion. The Cl- anion led to the initiation and development of the corrosion pits. The cathodic reaction was driven by hydrogen evolution reaction. The presence of filiform corrosion also proved a resistant oxide film naturally formed on the surface of Mg-8Y and Mg-5Y-7Gd-1Nd-0.5Zr alloys. The corrosion resistance of Mg-5Y-7Gd-1Nd-0.5Zr was better than Mg-8Y.
Mechanical Properties and Deformation Texture of GH536 Superalloy Strip
Authors: Jia Chong Lin , Fan Qiang , Wang Ying , Zhang Yong Yue , Li Qun
Published: March 2013

With cold rolling deformation between 12.5% and 60% for GH 536 superalloy strips, effect of deformation on the mechanical properties, texture formation and microstructure evolution have been investigated. The results show that an increase of deformation will lead to an increase of mechanical properties. As the deformation was 60%, the tensile strength and yield strength of the strip were 1430MPa and 1370MPa, respectively, and the elongation of strip was 4.5%. Also, an increase of deformation will lead to an increase of hardness, yield ratio and deformation resistance as well as an increase of rolling textures such as Goss {110}<001>, S{213}<4>, Copper {112}<1> and especially Brass {110}<12>. The optimized processing parameters of cold rolling deformation between 25% and 37.5% have been proposed to obtain an excellent formability and cold workability for GH 536 superalloy strips.
Effect of Heat Treatment on the Microstructure and Property of TiAl Alloys Prepared by Gas Atomization Powders
Authors: Liu Na , Li Zhou , Zhang Guo Qing , Yuan Hua , Xu Wen Yong , Gao Zheng Jiang
Published: March 2013

Powder metallurgical TiAl alloy was fabricated by gas atomization powders, and the effect of heat treatment temperature on the microstructure evolution and room tensile properties of PM TiAl alloy was investigated. The uniform fine duplex microstructure was formed in PM TiAl based alloy after being heat treated at 1250/2h followed by furnace cooling (FC)+ 900/6h (FC). When the first step heat treatment temperature was improved to 1360/1h, the near lamellar microstructure was achieved. The ductility of the alloy after heat treatment improved markedly to 1.2% and 0.6%, but the tensile strength decreased to 570MPa and 600MPa compared to 655MPa of as-HIP TiAl alloy. Post heat treatment at the higher temperature in the alpha plus gamma field would regenerate thermally induced porosity (TIP).
Microstructure and Hot Tearing Susceptibility of K418 and K419 Superalloy for Auto Turbocharger Turbine Wheel
Authors: Shi Zhao Xia , Dong Jian Xin , Zhang Mai Cang
Published: March 2013

K419 superalloy turbine wheel was more susceptible to hot tearing than K418 one when they were used for auto turbocharger turbine wheel. The fracture and microstructure characteristics in the K418 and K419 turbine wheel blades were analyzed. The segregation of alloying elements was analyzed by EDS. The probable equilibrium phases in the two kinds of superalloys, the effects of aluminum, titanium and niobium contents on the precipitation of γ and γ/γ eutectic phase and the segregation of alloying elements were studied by Thermo-Calc software. The results show that the hot tearing in the K418 and K419 superalloy turbine wheel blades is caused by the fracture of dendrites structures, while the amount of γ/γ eutectic in K419 is more than that in K418, resulting in K419 being more susceptible to hot tearing. Titanium and niobium, the strong positive segregation elements promote the formation of γ/γ eutectic, which lead to severe hot tearing susceptibility of the superalloy.
Effect of Solid Solution Heat Treatment on Microstructures of the Third Generation Single Crystal Superalloy DD9
Authors: Wang Xiao Guang , Li Jia Rong , Shi Zhen Xue , Liu Shi Zhong
Published: March 2013

An observation was conducted on the microstructures of as-cast as well as solid solution treated the third generation single crystal superalloy DD9 using optical microscope and SEM. The effects of solid solution temperature and time on the eutectic fractions of γ/γ and size of γ of the alloy were investigated. The results showed that the microstructure of DD9 was uniform. W and Re segregated to the dendrite cores while Al, Ta and Nb were enriched in interdendritic regions during solidification. The eutectic fractions of γ/γ reduced with the solid solution temperature raising and the solid solution time prolonging. When solid solution temperature increased to 1340, the eutectic in the alloy was entirely dissolved. The size of γ in dendritic cores was consistent, however the size of γ in interdendritic regions was gradually decreased with the increase of solid solution treatment and time, eventually the sizes of γ were completely uniform at the temperature of 1340
Quantitative Analysis on Fatigue Fracture of Spray Formed GH738 Alloy
Authors: Yang Dong Ye , Xu Wen Yong , Li Zhou , Zhang Guo Qing , Ning Zhing Liang , Sun Jian Fei
Published: March 2013

Low-cycle fatigue (LCF) fracture of the spray formed GH738 alloy was investigated under total strain controlled mode at 650°C. Basic theory for evaluating fatigue lives by fatigue striations has been introduced. The crack length a and the crack propagation rate da/dN were measured and the curve of da/dN in crack propagation zone was obtained with Paris formula and tabulation trapezoidal formula, respectively. The size and symmetry of rapid fracture zone of fatigue were also studied. The results showed that the relationship of a and N was linear with tabulation trapezoidal formula, and the da/dN and a was conic with Paris formula. At last, quantitative analysis of fatigue fracture was also discussed.
Preparation and Oxidation Behaviour of an Al-Si Coating on a Ni3Al Based Single Crystal Superalloy IC21
Authors: Liu Yu Zhuo , Wu Qiong , Li Shu Suo , Ma Yue , Gong Sheng Kai
Published: March 2013

An Al-Si coating was prepared on IC21 alloy by powder pack cementation. The cyclic oxidation tests were carried out at 1150 in air for up to 100 h. The results indicate that the oxidation resistance of IC21 alloy is significantly improved by the Al-Si coating due to the presence of Ni2Al3 and β-NiAl enriched outer layer, and Si can effectively supress the outward diffusion of Mo. The oxide scales mainly consist of α-Al2O3, which is the favorite to the oxidation resistance. Phase transformation occurred from β-NiAl to γ-Ni3Al and γ-Ni in the coating during oxidation. The coating still remained a certain amount of β phase after oxidation for 100h, which indicate a good protection. The microstructure change evolution was characterized, and the oxidation behavior of the coating was discussed.
Microstructure Evolution and Processing Map of Superalloy GH720Li during Isothermal Compression
Authors: Li Zhao , Fu Shu Hong , Wang Tao , Zhao Yu Xin , Zhang Yong , Zhang Mai Cang
Published: March 2013

sothermal compression tests for superalloy GH720Li were conducted to investigate the effect of hot deformation parameters on microstructure evolution. The changing characteristics of flow stress during hot deformation were also studied. The flow instability area was calculated based on Prasad Plastic Instability Criterion and the hot processing map was obtained. The results showed that dynamic recrystallization was the main softening mechanism of GH720Li alloy during hot deformation. The peak and steady stress decreased significantly with an increase of test temperature and a decrease of the strain rate. Finally, three unstable areas have been found from the processing map.
Superalloys and the Development of Advanced Ultra-Supercritical Power Plants
Authors: Xie Xi Shan , Chi Cheng Yu , Zhao Shuang Qun , Dong Jian Xin , Lin Fu Sheng
Published: March 2013

A 700 advanced ultra-supercritical (A-USC) power plant technology project was initiated in China in the year of 2011. The highest temperature components in A-USC boiler are superheater and reheater tubes. The fire-side metal temperature can reach 750 (even higher). Based on the very long time service (30-40 years) these important high temperature tubes require 105h long time stress rupture strength higher than 100MPa and the corrosion/oxidation layer loss less than 2mm for 2×105h. The highest temperature components in 700 steam turbine are the buckets of different stages and require very long service time. At this severe condition only superalloys can fulfill these unusual requirements. This paper reviewed Fe-Ni and Ni-base superalloys from the view point of structure stability and long term mechanical properties and corrosion/oxidation resistance for 700 A-USC power plant materials selection.
Influence of Annealing Time on Microstructure of Ni-W Alloys
Authors: Zhang Qiao , Liang Shu Hua , Zhang Chen , Zou Jun Tao
Published: March 2013

The as-cast Ni-W alloys with 15wt%W, 25wt%W and 30wt%W were annealed in hydrogen at 1100. The effect of the annealing time on the microstructure of Ni-W alloys was studied, and the phase constituents and microstructure of annealed Ni-W alloys were characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that no any phase changed for Ni-15%W, Ni-25%W and Ni-30%W alloys annealed for 60 min, 90 min and 150 min, which were still consisted of single-phase Ni (W) solid solution. However, microstructure had a significant change after annealing. With increase of annealing time, the microstructure of Ni-15%W alloy became more uniform after annealing for 90 min, and the average grain size was 95μm, whereas the grain size of Ni-15%W alloy increased significantly after annealing for 150 min. For Ni-25%W and Ni-30%W, there was no obvious change on the grain size with increase of annealing time, and the amount of oxides at grain boundaries gradually reduced. After annealing for 150 min, the impurities at grain boundaries almost disappeared. Subsequently, the annealing at 1100 for 150 min was beneficial for the desired microstructure of Ni-25%W and Ni-30%W alloys.
Influence of Withdrawal Rate on Tensile and Stress Rupture Properties of the Single Crystal Superalloy DD9
Authors: Shi Zhen Xue , Li J.R. , Liu Shi Zhong
Published: March 2013

The third generation single crystal superalloy DD9 was processed with different withdrawal rates and the effect of withdrawal rate on the tensile and stress rupture properties of the alloy was investigated. The relation between the mechanical properties and microstructure of the alloy with different withdrawal rates was discussed. The results showed that the withdrawal rate had a little effect on the tensile properties at 25 of the alloy. The tensile strength at 980 and stress rupture life at 1120/140MPa of DD9 alloy all increased with the increasing of withdrawal rate. The γ precipitates of specimen tensile at 25 had a little extension in the stress orientation. The extension of γ precipitates in the stress orientation at 980 was much more than that at 25. The vertical γ matrix at 980 became thinner and horizontal γ matrix became thicker slightly. The γ precipitates of those had rafted in a direction transverse to the applied stress.
Effects of Nb/Ti Ratio on the Microstructures of Two Experimental Ni-Based Cast Superalloys
Authors: Sun W. , Qin X.Z. , Wang W. , Wang T.T. , Guo Yong An , Guo J.T. , Lou Lang Hong , Zhou Lan Zhang
Published: March 2013

Effects of Nb/Ti ratio on the microstructures of two experimental Ni-based cast superalloys of the Nb/Ti ratio 0.46 and 0.03 were investigated. The Nb/Ti ratio had a significant effect on the dendritic microstructures, especially the γ precipitate, of the two alloys under the as-cast condition. The amount and composition of primary MC carbides were closely related to the Nb/Ti ratio for that the Nb atoms have a stronger tendency to form the MC carbides than the Ti atoms. During thermal exposure, the primary MC carbides gradually degraded through two reactions: firstly MC + γ M6C + γ and then MC + γ M23C6 + γ. The Nb/Ti ratio had little influence on the reaction formation but obvious influence on the decomposition degree of the primary MC carbides decomposition. In addition, the second M6C and M23C6 carbides on the boundaries (GBs) gradually formed a continuous chain during thermal exposure. The γ-free zones appeared along the GBs as the growth of the second carbides and γ precipitates on the GBs when thermal exposure time last up to 3000 h.