bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Mechanical Property of Mg-Zn-Y Alloy with a Long Period Ordered Phase
Authors: Itoi Takaomi , Kuroda Yasuki , Kawamura Yoshihito , Hirohashi Mitsuji
Published: June 2010

The composition dependence of yield strength and elongation of the Mg-Zn-Y ternary alloy system were investigated. Yield strength was found to increase with the increasing Zn and Y contents, while elongation decreased in Zn- and Y- rich- regions in the system. The composition ratio of Zn to Y, both of which shows large elongation and comparatively high yield strength, was 1:1 in the Mg-rich region of the alloy system. Mg98Zn1Y1, Mg96Zn2Y2, and Mg94Zn3Y3 (at.%) cast alloys exhibited yield strength of 107, 129, and 173 MPa, and elongations of 17, 8, and 12 %, respectively. These alloys consist of Mg-, LPO-, and Mg3Zn3Y2- phases. We also prepared Mg-Zn-Y alloy sheets by hot rolling using cast alloys, and we investigated their microstructure and mechanical properties. The Mg98Zn1Y1, Mg96Zn2Y2, and Mg94Zn3Y3, alloy sheets exhibited yield strength of 276, 319, and 379 MPa, and elongations of 12, 11, and 8 %, respectively. After annealing at 673 K for 3 h, large elongations above 20 % were achieved both of the Mg98Zn1Y1 and Mg96Zn2Y2 alloy sheets.
Formation of a Novel X Phase in Mg–Gd–Zn–Zr Alloy
Authors: Wu Y.J. , Peng Li Ming , Zeng X.Q. , Lin D.L. , Ding W.J.
Published: June 2010

The coherent fine-lamellae consisting of the 2H-Mg and the 14H-type long period stacking ordered (LPSO) structure within α'-Mg matrix have been observed in an as-cast Mg–Gd–Zn–Zr alloy. During subsequent solid solution heat treatment at 773 K, in addition to the lamellae within matrix, a novel lamellar X phase [Mg–(8.37±1.0)Zn–(11.32±1.0)Gd] with the 14H-type LPSO structure was transformed from the dendritical β phase. The 14H-type LPSO structure existing in Mg–Gd–Zn–Zr alloys derives from two variant ways: formation of the 14H-type LPSO structure comes from two variant means: i.e., the formation within matrix and the phase transformation from the β phase to the X phase in grain boundaries.
TEM Observation of Precipitates in a Mg-Gd-Sc Alloy with High Content of Sc
Authors: Fujii Takafumi , Kawabata Tokimasa , Matsuda Kenji , Ikeno Susumu
Published: June 2010

Precipitates in a Mg–Gd–Sc alloy with high Sc content (up to 13mass%) were examined by means of transmission electron microscopy. Plate-like precipitates appeared during the early stages of aging of specimens aged at 573 K. The plate-like precipitates lay on the { } magnesium matrix planes, and were similar to the β1 phase and β phase in the counterpart Mg–Gd–Zr alloy aged at 523 K. These precipitates had a high Sc content. Particle-shaped precipitate were observed alongside the plate-like precipitates, unlike the case in Mg–Gd alloys. The contrasts of the plate-like precipitates became longer and the number density of precipitate contrasts increased with increasing aging time at 573 K up to the point where the maximum hardness was attained. We suggest that the plate-like precipitates contribute to the increased hardness of Mg–Gd–Sc alloys with a high content of Sc.
Effect of Sc Addition on Aging Behavior of Mg-Gd Alloys
Authors: Kawabata Tokimasa , Matsuda Kenji , Ikeno Susumu
Published: June 2010

The effects of addition of Sc on the aging behavior of Mg–Gd alloy was examined by means of Vickers microhardness measurements, transmission electron microscopy (TEM), and high-resolution TEM. The maximum hardness of the specimens increased with increasing Sc content. In the early stages of aging, contrasts of precipitates that were similar to the β'' phase (D019-type structure) in binary Mg–Gd alloy were observed in the Mg–Gd–Sc alloys, whereas specimen that had started to harden again, but had not attained maximum hardness, showed predominant contrasts for precipitates that were similar to the β' phase (base-centered orthorhombic structure) in binary Mg–Gd alloy. Contrasts for precipitates with a D019-type ordered structure appeared during prolonged aging in specimen with high contents of Sc. Therefore, the addition of Sc to Mg–Gd alloys tends to slow down the transformation from the '' phase to the ' phase.
Microstructures and Mechanical Properties of Mg-9Zn-Zr Magnesium Alloys
Authors: Zhang Jing , Ma Qi , Pan Fu Sheng , Zuo Ru Lin
Published: June 2010

The effects of rare earth addtition of Er on the microstructures and mechanical properties of Mg-9Zn-Zr magnesium alloys were examined. The results showed that the addition of Er resulted in the formation of two types of thermally stable Er-bearing compounds with distinct Zn/Er ratio. The volume fraction of the second-phase particles increased with the increase of Er addition. 2% Er could refine the as-cast microstructure effectively. The yield strength generally increased and the elongation decreased gradually. 0.5% Er-bearing alloy had optimum combined mechanical properties, with the yield strength, tensile strength and elongation being 313MPa, 366MPa and 22%, respectively. Furthermore, addition of Er brought about homogenous deformation behaviour and recrystallization behaviour to the alloy.
Study on Mechanical Properties and Microstructures of Mg-6Zn-2Gd-0.6Zr New Sand-Casting Magnesium Alloy
Authors: Yang Guang Yu , Li Jie Hua , Jie Wan Qi , Yu Zhong
Published: June 2010

A new composition sand-casting magnesium alloy, Mg-6Zn-2Gd-0.6Zr, was developed. It was found that the room temperature mechanical properties of the alloy were superior: b=270MPa, 0.2=175MPa, =8%. Meanwhile, the elevated-temperature strength and creep resistance were significantly improved, comparing with Mg-5Zn-0.6Zr (ZK51) commercial magnesium alloy. The as-cast microstructure of the alloy was mainly consisted of (Mg) matrix, (+Mg3Gd2Zn3+Mg3Gd) eutectic phase, which was distributed along the (Mg) grain boundary with coarse netted shape. After solid-solution treatment and subsequently aging treatment for the alloy, the secondary phases re-precipitated as fine discontinues semi-netted or short rod-like precipitations, also including some fine spherical precipitations in the  matrix, which were responsible for the properties improvement of the alloy.
Effects of Trace Cu Addition on the Microstructure and Tensile Properties of ZK60 Alloy
Authors: Zhu Hong Mei , Luo Cheng Ping , Liu Jiang Wen , Liu Zong Wen , Ringer Simon P.
Published: June 2010

ZK60 alloy is one of the most important commercial wrought magnesium alloys. However, it suffers from several deficiencies like severe hot crack tendency and relatively low mechanical properties as compared to aluminum alloys. In this discussion, the microstructures of a ZK60-(0, 0.5 Cu, wt.%) alloy at different heat treatment states were examined by various techniques including optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corresponding room temperature tensile properties of the alloys were also tested. The results indicate that trace Cu addition could dramatically improve the casting properties and tensile performance of the ZK60 alloy. In the peak-aged condition, for example, the ultimate tensile strength and relative elongation were 261.4 MPa and 17.51% for the current ZK60-0.5Cu alloy, in contrast to 222.9 MPa and 5.97% for the ZK60 alloy, respectively. The improvements could be mainly attributed to the elevated number density and refinement of the dominant strengthening phase β1΄, together with the presence of C15 Laves phase MgZnCu formed in the ZK60-0.5Cu alloy. In addition, no appreciable change in yield strength was observed.
Effect of Casting Method and Al Contents on Microstructure in AM-Type Magnesium Alloys
Authors: Watanabe Katsumi , Matsuda Kenji , Gonoji Takumi , Kawabata Tokimasa , Sakakibara Katsuya , Sanpei Yukio , Saikawa Seiji , Ikeno Susumu
Published: June 2010

Magnesium alloys have received considerable attention because of their lightweight and recyclability. AM-type and AZ-type Mg-Al alloys have been used for industrial products widely, particularly for AM-type alloys because of the better toughness and impact absorption properties than AZ-type alloys. However, there is little report about the effect of casting method on age-hardening behavior and microstructure of AM-type alloys. The purpose of this study is to investigate the difference of the age-hardening behavior and microstructures of three AM-type alloys cast with steel, copper and sand molds using hardness test and scanning electron microscopy (SEM) observation. Furthermore, the effect of Al content is also investigated in this study using three alloys of AM30 (3%Al), AM60 (6%Al) and AM90 (9%Al).
Microstructural Evolution of Rheo-Diecast AZ91D Magnesium Alloy with Gadolinium Addition
Authors: Zhang Jin Ling , Wang Xi Tao , He Yong , Wang Yan Li
Published: June 2010

The rheo-diecasting (RDC) process, a novel semi-solid processing technology, was used to produce cast components with high integrity, fine and uniform microstructure, and therefore enhanced performance. AZ91D samples with 1-3 mass%Gd were solidified by RDC process. It was found that under intensive forced convection, the primary α-Mg phase produced inside the twin-screw slurry maker had fine particle size, spherical morphology and uniform distribution throughout the samples. Microstructure observations showed that Gd addition resulted in the formation of Al2Gd which dispersed in the α-Mg matrix. The size and amount of β-Mg17Al12 phase was reduced and its continuity was broken, which was the main reason for improving mechanical properties of the AZ91D alloy at high temperatures. The amount of Al2Gd particles increased with increasing Gd addition. From EPMA quantitative analysis, almost all Gd reacted with Al, leading to the low concentration of Gd in the α-Mg matrix. The Vickers hardness increased monotonously from HV=50.4 to HV=67.3 with increasing amount of Gd. This improvement was attributed to the consummation of aluminum in melt by precipitation of the Al2Gd phases.
Microstructure and Aging Behavior in AM60 Magnesium Alloy Cast into Sand and Permanent Molds
Authors: Yamada Hiroshi , Furui Mitsuaki , Ikeno Susumu , Sanpei Yukio , Sakakibara Katsuya , Saikawa Seiji
Published: June 2010

AM60 magnesium alloy castings gave the solution treatment at 688K for 86.4ks. After that, aging treatment was carried out at three temperatures of 473, 498 and 523K. The age hardening curve obtained, hardness of all the specimens in the condition of peak aging was increased by decreasing the aging temperature. In the condition of long aging time, a cellular precipitation grows up from grain boundary to crystal grain. Fine cellular precipitation and intergranular precipitation obviously occurs at the lower aging temperature.
Development of Heat-Resistance and Creep-Resistance Magnesium Alloy of Die-Casting Mg-4Al-4La and/or Ce
Authors: Meng Jian , Zhang Jing Huai , Zhang De Ping , Tian Zheng , Sun Wei , Lu Hua Yi , Tang Ding Xiang
Published: June 2010

Several Mg-4Al-4La/Ce alloys were developed and their microstructure and mechanical properties were evaluated. The phase compositions of Mg-4Al-4La alloy consist of α-Mg and Al11La3 phases. While two binary Al-RE phases, Al11RE3 and Al2RE (RE=Ce/La), are formed in Mg-4Al-4Ce/La alloy, and Al11Ce3 and Al2Ce are formed in Mg-4Al-4Ce alloy. The optimal tensile properties are obtained in Mg-4Al-4Ce/La alloy, in which the UTS, YS and δ are 250, 149.2 MPa and 12.24% at room temperature, and 157.8, 116 MPa and 27% at 150oC, and 99.1, 118.2 MPa and 23.2% at 250oC, respectively. The mechanics properties of Mg-4Al-4Ce/La alloy are nearly same with commercial AE44. The compression creep is lower than that AJ62 alloy.
Influence of Grain Boundary on Activation of Slip Systems in Magnesium: Crystal Plasticity Analysis
Authors: Mayama Tsuyoshi , Ohashi Tetsuya , Higashida Kenji
Published: June 2010

Crystal plasticity finite element analysis method considering the accumulation of geometrically necessary (GN) dislocations was applied to monotonic loading of pure magnesium bi-crystal. The deformation mechanisms considering in the present analysis method are basal slip , prismatic slip , 1st order pyramidal slip , 2nd order pyramidal slip  and tensile twinning . Tensile twinning is incorporated into crystal plasticity analysis assuming that twinning plane and direction of shear by twinning are equivalent to slip plane and slip direction, respectively. Critical resolved shear stresses (CRSSs) for each slip system in the literatures were used. Analysis model is designed to investigate the influence of grain boundary on the activation of slip systems. That is, one grain consisting of bi-crystal (grain A) had the crystal orientation whose Schmid factor for prismatic slip is 0.5. The crystal orientation of the other grain (grain B) was slightly deviated from that of grain A. The result of the calculation of tensile loading of the bi-crystal showed that both grains are deformed by the multiple slip of basal slip system, which resulted in the formation of GN dislocation bands.
Crystallography of Ferrite Nucleation at Austenite Grain Boundary in a Low Carbon Steel
Authors: Furuhara Tadashi , Saito Hayato , Miyamoto Goro , Maki Tadashi
Published: June 2010

Orientation relationships of proeutectoid ferrite formed at an austenite grain boundary with respect to adjacent austenite grains were investigated by means of electron backscatter diffraction in an isothermally transformed Fe-1.5Mn-0.2C (mass%) alloy. A grain bounadry ferrite holds nearly the Kurdjumov-Sachs (K-S) orientation relationship with some small misorientation against at least one of the adjacent austenite grains. There is strong variant selection by the austenite grain boundary for ferrite nucleation. At a higher transformation temperature, the fraction of ferrites holding a near K-S relationship with respect to the opposite austenite grain is lower. As the transformation temperature becomes lower, the misorientation from the K-S relationship becomes smaller against the near K-S related austenite grain whereas the misorientation against the irrationally oriented austenite grain becomes larger.
Twinning-Induced Negative Strain Rate Sensitivity in Wrought Magnesium Alloy AZ31
Authors: Chun Y.B. , Davies Chris H.J.
Published: June 2010

Measurements of strain rate sensitivity (SRS) provide a key link between dislocation-based interpretations of plastic deformation and macroscopic measurements made in mechanical tests. It is well known that plastic deformation of hexagonal close-packed (hcp) metals is achieved not only by dislocation glide but also by twinning and that the atomic rearrangement underlying the latter mode is different from that of slip. This leads to an expectation that co-activation of twinning may affect SRS of hcp metals. This assumption was tested in the present work where strain rate jump tests in both tension and compression were conducted on highly textured AZ31 plate. It was found that the SRS of the alloy in tension decreased with strain whereas that in compression increased with strain, exhibiting negative values at low strain and positive values at higher strain. Microstructure analyses revealed that the strain regimes where negative SRS or decreasing trend in SRS with strain was observed correspond to extensive twinning, implying a negative SRS of twinning. It is concluded that dislocation model alone cannot explain the strain rate dependence of flow stress in metals whose deformation is assisted by twinning.
Grain Refinement of Magnesium Alloy AZ31 under Torsion Extrusion with a Square-Hole Die
Authors: Mizunuma Susumu , Iizuka Takamichi , Mitsui Kazuhiro , Okumura Hidehito , Kohzu Masahide
Published: June 2010

Grain refinement and crystal orientation of magnesium alloy AZ31 under torsion extrusion with a square-hole die are investigated. The optimum temperature and ratio of the die rotation speed to the extrusion speed were clarified, resulting in uniformly distributed fine grains with sizes in the range 1- m over the entire cross section of the worked specimen. The crystal orientation of the specimen was determined by electron backscatter diffraction and compared with that of a conventionally extruded specimen. In the case of torsion extrusion, a very strong <0001> texture was observed along the extrusion axis, especially in the center region of the cross section. In contrast, the <0001> direction of many grains in the conventionally extruded specimen tended to be perpendicular to the extrusion axis.
Crystallographic Orientation Dependence of Fatigue Crack Propagation Behavior in Rolled AZ31 Magnesium Alloy
Authors: Morita Shigeki , Ohno Nobuyoshi , Tamai Fujio , Kawakami Yuji
Published: June 2010

This paper deals with fatigue crack propagation behavior of rolled AZ31B magnesium alloy. Two types of specimens with the loading axis parallel to rolling direction were machined; fatigue crack propagation direction was parallel to transverse direction (L-T specimen), and short transverse direction (L-S specimen). Fatigue crack propagation tests were performed with center cracked plate tension specimen with stress ratio R=0.1 and frequency of 10Hz at room temperature. Crack propagation rate of L-T specimen was approximately 10 times higher than that of L-S specimen. SEM-EBSD observations revealed that the c-axis direction is unfavorable for the fatigue crack propagation in textured polycrystalline magnesium alloy.
Microstructure Evolution in AZ31 Magnesium Alloy Worked by Torsion at Warm Temperature
Authors: Aoyama Koji , Furui Mitsuaki , Ikeno Susumu
Published: June 2010

It had been already reported that the resistance of compression at warm condition can be decreased by the preliminary torsion working at AZ31B magnesium alloy. In the present study, it was found that the dynamic recrystallization occured during warm working by torsion. Dynamic recrystallization was slightly seen in the fractured edge of the bar at a rotation speed of 1rpm at temperature 573K and 623K. The amount of torsion to fracture was increased with increasing of deformation temperature. Remarkable dynamic recrystallization could be seen in the center of bar at the rotation speed of 1rpm at temperature of 673K.
Deep Drawing of AM31 Magnesium Alloys
Authors: Cho Jae Hyung , Chang Li Li , Kang Suk Bong
Published: June 2010

Texture and microstructure evolutions during deep drawing of AM31 magnesium alloys were investigated at various temperatures and deformation rates. Two different types of sheets were fabricated by twin roll strip and conventional ingot casting. They were warm-rolled down to 0.6mm and then fully-annealed for deep drawing. Drawing temperatures were 200oC to 350oC and punch rates, 30mm/min, 40mm/min, and 50mm/min. The blank size and punch diameter were 74mm and 37mm, respectively, and thus overall maximum drawing ratio was 2.0. Processing maps for deep drawing of both sheets at elevated temperatures were suggested. Initial textures showed typical basal fibers with an axisymmetric arrangement. Sheets made by ingot casting had larger grain size than those by twin roll casting. The basal fibers were evolved into other orientations during deep drawing, which contained both compression along the circumferential direction in the flange and tension along the drawing direction in the cup wall. Most evident reorientations were found in the flange. With deformation, finer grains increased. Necking and cup-failure were usually expected in the lower wall near the bottom.
Grain Refinement by Combined ECAE/Extrusion and Dieless Drawing Processes for AZ31 Magnesium Alloy Tubes
Authors: Furushima Tsuyoshi , Shimizu Tetsuhide , Manabe Kenichi
Published: June 2010

Grain refinement processing by severe deformation, combined equal-channel angular extrusion (ECAE) processing and conventional tube extrusion, is applied to AZ31 magnesium alloy. By a combination of ECAE processing and tube extrusion, a fabricated tube, with outer and inner diameters of 2 mm and 1 mm, respectively, has fine, homogeneous, and equiaxed grain structure with an average grain size of 1.5m. Tensile test results indicate that the fine-grained tubes exhibited a superplasticity potential m value of 0.55.The maximum elongation (688%) is obtained at a temperature of 673K. Furthermore, the tubes fabricated by combined ECAE/extrusion process is applied to dieless drawing process without using any tool and die.As a result, dieless drawing limit is enhanced due to high m value achieved by combined ECAE/Extrusion process. From these results, the effectiveness of new grain refinement processing for fabricating fine-grained tubes and its application for dieless drawing process to fabricate the fine tubes was demonstrated experimentally.
Evolution of Different Recrystallization Textures in Steels Having {111}<112> Rolling Texture
Authors: Kim Se Jong , Han Heung Nam , Lee Dong Nyung
Published: June 2010

The Goss {110}<001> orientation, which is not stable with respect to plane strain rolling, rotates toward the {111}<112> orientation forming a strong maximum. The {111}<112> rolling component returns to the Goss orientation after recrystallization (Rex). On the other hand, the {111}<112> Rex texture developed in 65% rolled iron electrodeposit with a weak {111}<112> texture, and the {111}<110> Rex texture developed in 80% cold rolled electrodeposit having a strong {111}<112> texture. That is, the {110}<001>, {111}<112>, and {111}<110> Rex textures developed in bcc steels having the {111}<112> rolling textures. The results have been discussed by the strain-energy-release-maximization model for Rex texture.
Welding Interface in Magnetic Pulse Welded Joints
Authors: Watanabe Mitsuhiro , Kumai Shinji
Published: June 2010

Magnetic pulse welding was applied to the lap joining of similar (Al/Al) and dissimilar materials (Al/Fe, Al/Cu, and Al/Ni). The magnetic pulse welding is a kind of impact welding represented by explosive welding. The impact energy is induced by electromagnetic force generated by interaction among discharge pulse, induced magnetic flux, and eddy current produced at the plate surface. The welding was achieved within 10 microseconds with a negligible temperature increase. The welding interface exhibited a characteristic wavy morphology, which was similar to that of the explosive welding. In the Al/Fe, Al/Cu, and Al/Ni joints, an intermediate phase layer was produced along the wavy interface. In order to investigate microstructure of the intermediate phase layer, TEM observation of the welding interface was carried out. TEM observation revealed that the intermediate phase layer consisted of amorphous phase and fine crystal grains.
Characterization of Nickel Oxide Layers on the AZ91 Mg Alloys by Plasma Electrolytic Oxidation
Authors: Hwang In Jun , Lee Kang Min , Yoo Bong Young , Shin Dong Hyuk
Published: June 2010

Characterization of nickel oxide layers on the AZ91 Mg alloys by plasma electrolytic oxidation (PEO) was investigated. For this purpose, PEO coating was carried out on the present sample in the alkaline electrolyte with nickel ion at three different voltage responses, i.e., 150, 250, 350 V. The amount of nickel oxide increased by increasing process time, and changed the color of sample from light grey to moderate olive brown. It was observed from potentio-dynamic polarization analysis that polarization resistance of oxide layer was increased with increasing nickel ions. Also microhardness of the sample processed at 350 V was higher than those of the samples.
Continuous Casting of Magnesium Alloy Billet Using Electromagnetic Techniques
Authors: Kim Myoung Gyun , Kim Jong Ho , Park Joon Pyo , Lee Gyu Chang , Kim Woo Jin
Published: June 2010

Currently, magnesium billets produced by ingot casting or direct chill casting process, result in low-quality surfaces and peer productivity. Continuous casting technology for high-quality surface billets with fine-grained and homogeneous microstructure can be a solution for the cost barrier breakthrough. The latent heat of fusion per weight (J/g) of magnesium is similar to that of other metals, however, considering the heat emitted to the mould surface during continuous casting in meniscus region and converting it to the latent heat of fusion per volume, magnesium will be rapidly solidified in the mould during continuous casting, which induces subsequent surface defect formation. In this study, electromagnetic casting and stirring (EMC and EMS) techniques are proposed to control solidification process conveniently by compensating the low latent heat of solidification by volume and to fabricate magnesium billets with a high quality surface.
Production of Ti-6Al-4V Strip by Direct Rolling of Blended Elemental Powder
Authors: Cantin G.M. Delphine , Stone Nigel A. , Alexander David , Gibson Mark A. , Ritchie David , Wilson Robert , Yousuff Merchant , Rajakumar Raj , Rogers Kevin
Published: June 2010

A significant research effort within the CSIRO Light Metal Flagship is aimed at developing new processes for the manufacture of (semi-finished) titanium products based on a powder metallurgy approach. The main driver for considering alternative processing and consolidation techniques to conventional ingot metallurgy is improved techno-economics associated with a reduction in processing steps and increased productivity via rapid consolidation of parts. In this respect, CSIRO has developed a process to manufacture sheet products utilising direct powder rolling; the process consists of cold rolling the powder feedstock to a green strip, which is then rapidly heated and hot rolled to consolidate the material completely. The work reported here was an investigation into the feasibility of fabricating Ti-6Al-4V strip by a blended elemental powder metallurgy route. The development of microstructures occurring during the processing and heat treatment steps has been studied. The generic roles of some process, material and heat treatment variables on the tensile properties and homogeneity of the final material have been assessed and are discussed in this paper.
Mechanical Properties of Oxide Dispersion Strengthened Pure Titanium Produced by Powder Metallurgy Method
Authors: Yoshimura Tomohito , Thrirujirapaphong Thotsaphon , Imai Hisashi , Kondoh Katsuyoshi
Published: June 2010

Pure titanium has good specific properties i.e. low density of 4.5g/cm3, extremely high resistance for corrosion and good elongation. However, its mechanical properties are not enough to be employed as structural parts and components. Accordingly, titanium alloys are often applied to industrial fields due to their high specific strength. However, the application is limited to high-performance products because of their expensive material cost and poor plastic formability at low temperature. In the present study, from a view point of cost reduction, pure titanium was used as a starting material. The materials design by oxide dispersion strengthening (ODS) was basically applied to improve the poor mechanical strength of pure titanium. TiO2 powders were used as reinforcement dispersoids because of their easily obtainable and low material cost. Powder metallurgy (P/M) method was applied to fabricate TiO2 particles reinforced pure titanium composite. Pure titanium powder and TiO2 particles were elementally mixed by conventional mixing process. Their elemental mixture powders were consolidated by using spark plasma sintering (SPS) equipment to serve a high density compact billet. Subsequently, hot extrusion process was applied to the billet to prepare a full density rod specimen. The evaluation of mechanical properties at room temperature showed high tensile strength of 1040 MPa and good elongation of 25 % when the composite included 1.5mass% TiO2 particles.
Microstructural Evolution in Chips during Machining of Commercially Pure (Grade 2) Titanium
Authors: Sun Shou Jin , Brandt Milan , Song Wei Qian , Dargusch Matthew S.
Published: June 2010

Development of microstructure in chips during machining of Grade 2 titanium at different cutting speeds has been investigated. The morphology of the chip changes from continuous chip to irregular and regular segmented chip with increasing cutting speed. The deformation in continuous and segmented chips is characterized as continuous and localized shear respectively. The deformation mechanism in the irregular segmented chip is the dislocation slip in the continuous region and twinning around the localized shear. Deformation twinning was observed inside the segment between the shear bands in the regular segmented chip. These deformation twins are responsible for the hardening inside the segment.
Effect of Pore Size on Mechanical Properties of Titanium Foams
Authors: An Yang , Yang Chun Hui , Hodgson Peter , Wen Cui E
Published: June 2010

In the study, both experimental work and numerical modeling are performed to investigate the pore size effects on the mechanical properties and deformation behaviours of titanium foams. Cylindrical titanium foam samples with different pore sizes are fabricated through powder metallurgy. Scanning electron microscope (SEM) is used to determine the pore size, pore distribution and the ratios of the length to width of pores. Compressive tests are carried out to determine the mechanical properties of the titanium foams with different pore sizes. Finally, finite element modeling is attempted to simulate the deformation behaviour and the mechanical properties of the titanium foams. Results indicate that titanium foams with different pore sizes have different geometrical characteristics, which lead to different deformation behaviours of cell walls during compression, resulting in different mechanical properties of titanium foams.
Improvement in Hot Workability of Titanium Matrix Composite by Thermohydrogen Treatment
Authors: Lu Wei Jie , Lu Jun Qiang , Zhang Di , Hou Hong Liang
Published: June 2010

Ti-6Al-4V matrix composite (TMC) reinforced with TiB plus TiC was prepared and hydrogenated. Isothermal compression tests and high temperature tensile tests were carried out to study the effect of the hydrogen on hot deformation and superplastic deformation. The flow behaviour and microstructure evaluation of hot deformation was investigated. The results show hydrogen can reduce the flow stress and decrease the deformation temperature or increase the strain rate at the same flow stress level in hot deformation. Hydrogen increasing β phase and promoting dynamic recrystallizaiton (DRX) was considered as the main reasons for hydrogen-induced plasticity in hot deformation. The results of superplastic deformation indicate hydrogen can decrease the superplastic temperature 100°C or increase strain rate one order of magnitude at the same elongation level in superplastic deformation. Hydrogen promoting DRX were considered as the main reason for improvement of superplastic elongation.
Aging Response of TB-13 Titanium Alloy
Authors: Zhou Zhong Bo , Li Jin Shan , Kou Hong Chao , Zhu Zhi Shou , Tang Bin , Chang Hui
Published: June 2010

In order to develop a perspective of the new metastable β titanium alloy——TB-13, the influence of ageing treatments on the microstructure and properties has been studied. The results show that TB-13 alloy displays high age strengthening effect and fine precipitation. During the one-step aging process, the higher the aging temperature, the coarser the α plate thickness. As a result, TB-13 alloy shows the lower the strength and the higher the ductility. The best combination of strength and ductility is acquired in the TB-13 alloy after solution treatment at 1133K following aging at 813K for 16h. The ultimate strength is near 1400MPa and the specific elongation is 7.0% by ageing. At last, the details of the transformation mechanism and microstructural evolution accompanying ω-assisted α nucleation during continuous heating are discussed.
Microstructural Evolution of Medium Carbon Steels during the Quenching and Partitioning Process
Authors: Li Hong Yan , Jin Xue Jun
Published: June 2010

The “Quenching and Partitioning” (Q&P) process is a novel heat treatment designed for processing new generation advanced high strength steels (AHSS) with substantial ductility. In this study, evolution of complex microstructure for medium carbon steels during the Q&P process has been discussed in detail. Such steels have shown a complex multiphase microstructure consisted of fresh lath-martensite, fresh plate-martensite, transition carbide and/or cementite, isothermal martensite/lower bainite, and second twin-martensite after the one-step Q&P process (with the identical quenching and partitioning temperature). The morphology for the microstructure at room temperature after the two-step Q&P process (with different quenching and partitioning temperatures) demonstrated a little different. The formation of different microstructure for these two processes and their correlation with the mechanical properties are discussed.
Recent Developments in Mechanisms and the Kinetics of Deformation Twinning in Titanium Alloys
Authors: Wyatt Zane , Ankem Sreeramamurthy
Published: June 2010

Within the past decade, it has been shown that twinning in α, β, and α + β titanium alloys can occur at speeds much lower than the speed of sound by many orders of magnitude. This is related to the twinning deformation mechanisms controlled by the diffusion of oxygen as compared to simply a shear process. Very recent developments, such as strain-rate effects on twinning, support a recent hypothesis that the twinning in these materials is controlled by a slow diffusion process, resulting in time-dependent twinning. These recent developments, along with the ramifications of the findings will be outlined in this article.
Study on Tensile Property and Fracture of Welded Joint of Ti-6.5Al-2Zr-1Mo-1V Alloy by Hydrogen Processing
Authors: Wang Q. , Sun Dong Li , Yang Hui , Wang J.
Published: June 2010

The microstructural evolution of TIG welded joint in Ti-6.5Al-2Zr-1Mo-1V alloy treated by thermo hydrogen processing was investigated by optical microscopy, transmission electron microscopy and scanning electronic microscopy and the mechanical properties of welded joints were tested and analysed. The results showed that δ-hydride formed after hydrogenising at 700°C for 3 hours, and it is a face-centered cubic crystal. And these hydrides brought a strong fuzzy effect on microstructure. A lot of rhombic martensite phase α" generated in the area of welded joint. Metastable β(H) phase and α" phase were gradually decomposed to α and δ phases during aging. Hydrides were dissolved, the hydrogen was removed from the alloy and the recrystallization occurred in the process of annealing in vacuum. After hydrogen treatment, the refinement effect of grains in the fusion area was very obviously, that is, coarse columnar grains changed to finer equiaxed grains. Non-equilibrium phase reduced in grains. After hydrogen treatment (hydrogenization at 700°C for 3 hours, eutectoid at 300°C for 8 hours and annealing at 750°C for 8 hours in vacuum), the tensile strength of welded samples increased by 25.7%, and the elongation increased by 37.6% compared with welded samples without hydrogen treatment. After hydrogen treatment, the surface morphology of tensile fracture was relative flatness.
Influence of Solution Treatment on Microstructure and Quench Cracking in a Water-Quenched Aluminium Alloy 7150
Authors: Xu Dao Kui , Rometsch Paul A. , Chen Hua , Muddle Barry C.
Published: June 2010

In this work, the influence of multi-step solution (MSS) treatments on the constituent particle dissolution, overheating and associated quench cracking behaviour in room temperature water-quenched 7150 Al alloy has been investigated. For comparison, the microstructure and quench cracking behaviour of single step solution treated samples water-quenched from 505°C were also investigated. Based on optical microscopy of differently quenched samples, the quench cracking mode and the influence of overheating of constituents on the quench cracking behaviour have been demonstrated. The results reveal that the constituent particles can be effectively dissolved in the MSS-505°C samples. When the quench temperature of MSS-505°C samples is equal to or higher than 485°C , macro quench cracks can be clearly observed. Moreover, the density and length of the quench cracks increase with increasing quench temperature. Etched microstructures indicate that the quench crack propagation mode is intergranular. However, for samples directly heated to 505°C , typical overheating can be observed at the triple junctions and these regions preferentially act as crack propagation routes.
The Effect of Mn and Si on the Properties of Advanced High Strength Steels Processed by Quenching and Partitioning
Authors: Mašek Bohuslav , Jirková Hana , Hauserova Daniela , Kučerová Ludmila , Klauberová Danuše
Published: June 2010

The concepts new types of materials are, for economic reasons, focused mainly on low alloyed steels with a good combination of strength and ductility. Suitable heat and thermo-mechanical treatments play an important role for the utilization of these materials. Different alloying strategies are used to influence phase transformations. The quenching and partitioning process (Q-P Process) is one of the heat treatment methods which can result in a high ultimate strength as well as a good ductility. However, these good properties can be obtained only if a sufficient amount of retained austenite is stabilized. The influence of different contents of manganese, silicon and chromium on microstructural development and mechanical properties were experimentally tested. Alloying elements were used to stabilize the retained austenite in the final microstructure and also to strengthen the solid solution. Ultimate strengths of over 2000MPa with ductility over 10% were reached after the optimization of the Q-P Process. The microstructures were analyzed using several microscopic methods; mechanical properties were determined by a tensile test and the volume fraction of the retained austenite was established by X-ray diffraction phase analysis.
Understanding the Directional Dependence of Intergranular Corrosion in Aluminium Alloys
Authors: Knight Steven P. , Clark Graham , Davenport A.J. , Trueman Anthony R.
Published: June 2010

Intergranular corrosion can lead to significant problems such as sub-critical crack growth or loss in section strength, potentially leading to failure, as well as a substantially increased maintenance burden. This type of corrosion is found in most types of aluminium alloys, but is a particularly significant problem in aerospace aluminium alloys. The form of intergranular corrosion can vary widely, and may depend on alloy composition, product form, environmental conditions and the presence or otherwise of local or global stresses. One notable example is the occurrence of intergranular corrosion due to atmospheric corrosion, in which salts and deposits deliquesce on the surface forming discrete corrosion cells. Intergranular corrosion of aluminium alloys is usually most rapid in the rolling or extrusion direction of wrought alloy. The reasons for this are not fully understood, and may include texture effects that produce highly susceptible grain boundaries, the inhomogeneous distribution of noble constituent particles, and stresses acting at a microscale. This paper will review and discuss the evidence for and against for the different effects mentioned.
Experimental Investigation of the Dynamic Behavior of Aluminum Foams
Authors: Xu Shan Qing , Ruan Dong , Beynon John H. , Lu Guo Xing
Published: June 2010

The compressive behavior of two closed cell aluminum foams (Alporas and Cymat) were investigated under various strain rates from 10-3 to 102 s-1 using compressive tests conducted on MTS and Instron test machines. High speed camera videos show that localized deformation occurs in Alporas foam specimens uniformly, but not in Cymat foams. The stress-strain curves for Alporas foams are smooth and regular, while they oscillate dramatically for Cymat foams. Alporas foams exhibit strain rate sensitivity, i.e. with an increase in strain rate, the normalized plateau stress and energy absorption capacity increase. The plateau stress for Cymat foams was more sensitive than Alporas to strain rate, but the energy absorption less so, at least at a nominal relative density of 10%.
Alloy Design for Enhancing the Fracture Resistance of Heat Treated High Pressure Die-Castings
Authors: Lumley Roger N. , Gershenzon Maya , Gunasegaram Dayalan R.
Published: June 2010

Recently, heat treatment technologies have been developed by the CSIRO Light Metals Flagship in Australia that allow the 0.2% proof stress of conventional aluminum alloy high pressure diecastings (HPDC’s) to be more than doubled without encountering problems with blistering or dimensional instability [1,2]. A range of other properties may also be improved such as fatigue resistance, thermal conductivity and fracture resistance. However, the current commercial HPDC Al-Si-Cu alloys have not been developed to exploit heat treatment or to optimize these specific mechanical properties, and one potential limitation of heat treating HPDC’s is that fracture resistance may be reduced as strength is increased. The current paper presents the outcomes of a program aimed at developing highly castable, secondary Al-Si-Cu HPDC alloys which display significantly enhanced ductility and fracture resistance in both the as-cast and heat treated conditions. Kahn-type tear tests were conducted to compare the fracture resistance of the conventional A380 alloy with a selection of the newly developed compositions. A comparison has also been made with the current permanent mold cast aluminium alloys and it is shown that the new HPDC compositions typically display higher levels of both tensile properties and fracture resistance.
Refinement of TiB2 in Al-Ti-B Grain Refiner Alloys by Ultrasound and the Effect on Al Grain Size
Authors: Shu Da , Sun Bao De , Mi Jia Wei , Grant Patrick S.
Published: June 2010

High-intensity ultrasound was applied during the preparation of an Al-5Ti-1B master alloy when reacting fluoride salts with molten Al. The reaction rate was significantly increased with TiB2 particles of much reduced mean diameter and narrow width spread produced in ~4 minutes. The improved grain refining performance of the TiB2 in a commercial purity Al was studied and modelled using free growth model. The increased number and reduced size of TiB2 particles provided an enhanced grain refining capability.
Microstructural Evolution in Various Regions of Stir Zone during Friction Stir Processing of Al-7Si-0.3Mg Cast Alloy
Authors: Chen Zhanwen , Cui Song , Gao Wei , Zhu Tian Ping
Published: June 2010

Castings may be used more as structural components if friction stir (FS) processing could refine the microstructures satisfactorily. For this, material flow and the formation of various microstructural regions during FS were studied. It was found that -Al dendrites and eutectic Al-Si were sheared into the thread spaces and the microstructures were significantly modified and refined. Material merely dragged into the FS zone remains microstructurally segregated. The volume of each flow was affected by rotation speed and forward speed and the reason for this is explained. Finally, textures determined together with the strain values estimated are presented to discuss further the microstructual development in various stir zones.
Application of Laser Remote Welding to an Aluminum Automotive Part
Authors: Kim Cheol Hee , Choi Won Ho , Park Ki Young
Published: June 2010

Aluminum alloys are extensively used in the automotive industry in response to increasing requirements for weight reduction in car body architecture. Laser welding of Al alloys has many advantages such as low heat input, narrow heat affected zone, minimal thermal distortion and flexibility. Recently, the development of high brightness lasers - thin disk lasers and fiber lasers enable long focal distance welding so that laser remote welding with scanning mirrors can be used in laser welding of Al alloys. In this study, laser remote welding was implemented to a heat shield part of an automobile by utilizing a 4kW disk laser and a 2-axis scanner. By replacing conventional resistance spot welding, the weld flange length could be reduced from 15mm to 8mm and a cycle time for each welding point could also be reduced from 3.5s to 0.6s.
Roll Casting of Al-SiCp Strip
Authors: Nakamura Ryoji , Nakamura Teppei , Kumi Sinji , Watari Hisaki
Published: June 2010

Al-SiCp aluminum alloy has some useful advantages i.e., low thermal expansion, better thermal conductivity and wear resistant. Recently, plates of Al-SiCp with thickness less than 1mm was demanded. The Al-SiCp is hard and brittle. Therefore, only hot rolling was a useful process to make thin plate. In the present study, roll casting of Al-SiCp strip was tried by a vertical type high speed twin roll caster to evaluate energy savings. The Al-SiCp strip, with thickness about 2mm, was cast directly from the molten metal. The particles of SiC were dispersed uniformly. The as-cast Al-SiCp could be coiled. The roll cast Al-SiCp had superior ductility. For this reason, the eutectic Si in matrix aluminum alloy (Al-Si alloy) became fine and globular. Cold rolling could be operated after 1-pass of hot rolling. The 1mm-thick Al-SiCp plate could be made by one-pass of hot rolling and 3-passes of cold rolling and annealing from as-cast strip.
The Isothermal Transformation of Low-Alloy Low-C CMnSi Steels below MS
Authors: Kim Dong Hwi , Speer John G. , De Cooman Bruno C.
Published: June 2010

An isothermal transformation was observed when a low-alloy, low-carbon steel was quenched and held in the MS–Mf temperature range after austenitized above A3. The precise nature of this isothermal transformation is still unclear. The present contribution is a comprehensive comparison using EBSD, internal friction (IF) and TEM analysis of the isothermal transformation product, the athermal martensite and the lower bainite. The observations revealed that the isothermal transformation product in the MS-Mf temperature range had its own microstructural characteristics with wavy lath boundaries and orientation relationship.
Untrasonic-Assisted Fabrication of SiC Nanoparticles Reinforced Aluminum Matrix Composites
Authors: Li Wen Zhen , Liu Shi Ying , Zhang Qiong Yuan , Zhu Xue
Published: June 2010

SiC nanoparticles reinforced ADC12 aluminium alloy nanocomposites were synthesized by mechanical stirring and high-intensity ultrasonic dispersion processing. SEM analysis results showed that SiC nanoparticles were dispersed and distributed very well in the alloy matrix. TEM results suggested that SiC bonds well with matrix without forming an intermediate phase. The strength and ductility of the nanocomposites were improved simultaneously.
Effect of Rapid Solidification Processing on Hydrogen Behaviour in Aluminium
Authors: Tashlykova-Bushkevich Iya I. , Shikagawa Takahiro , Shepelevich Vasiliy G. , Itoh Goroh
Published: June 2010

Thermal desorption spectroscopy (TDS) technique has been used to study hydrogen behaviour in rapidly solidified (RS) aluminium (Al) both as-cast and exposed to humid air (HA). The surface morphology of the foils was studied through atomic force microscopy (AFM). Analysis was made of the effect of rapid solidification processing (RSP) on H/microstructure interactions, including investigation of alloying element (0.05 at % Ti) influence on H trapping in Al.
Self-Tuning Controller for Nonlinear Object
Authors: Nawrocka Agata , Kwaśniewski Janusz
Published: June 2010

The main subject matter of the paper is the application of adaptive control systems. This type of control is particularly useful for processes and machines with variable parameters. Classic controllers in this case are not satisfactory. Therefore a research work was initiated on advanced algorithms of control. The paper analyzes algorithms based on fuzzy logic. It should be noted that parameters of fuzzy controllers require adjustment to changeable process (machine) parameters for which an adaptive mechanism is required. The proposed algorithm has been tested on a laboratory stand with a hydrostatic transmission, which is a non-linear and a non-stationary object.