bluuebunny/crossref_metadata_2025 huggingface dataset:
Rolling Contact Fatigue Type Analysis of Rolling Bearing by XRD and TEM
Authors: Hidaka H. , Ueda Kouji , Mitamura N.
Published: January 2012

In the rolling bearing, the flaking caused by rolling contact fatigue is classified into two types: surface originated flaking and subsurface originated flaking. It has been recognized that marked microstructural change can occur in subsurface originated flaking due to rolling contact fatigue. But there are few reports in surface originated flaking about microstructural change. In this study, surface originated flaking caused by rolling contact fatigue was investigated based on microstructural change. Thrust ball bearing and radial ball bearing was used for fatigue test. Simulation of dent originated flaking was carried out using the bearing with artificial dent. Another fatigue test subjected to surface originated flaking was done under shortage of oil film thickness lubrication condition. Microstructural change was measured by X-ray Diffractmetry (XRD) and Transmission Electron Microscopy (TEM) during fatigue testing. Microstructure of bearing steel used for fatigue test is consisted of martensite with small amount of retained austenite. XRD measurement reveals that the half peak width of martensite and volume fraction of retained austenite decreasing with increasing testing time, and the amount of decrease in these parameter were small in the surface originated flaking compared with subsurface originated flaking when the specimens were flaking. This suggests that surface originated flaking occurs in spite of mild microstructural change. TEM observation about the surface originated flaking shows plastic flow in the surface layer. Especially, it was confirmed that partial recrystallization occurs in the fatigue test under shortage of oil film thickness lubrication condition. But it was also confirmed that degree of recrystallization is lower in the surface originated flaking than subsurface one, and this reasonably explains XRD result. From these results, it was cleared that recrystallizaiton of martensite is differ in degree but not in kind between surface originated flaking and subsurface originated flaking.
Residual Stress Analysis of Stellite-Coated Forging Tool Steel Using Synchrotron Radiation Diffraction
Authors: Toumi M.Y. , Benmarouane A. , Bonnefoy Herve , Buslaps Thomas , Lodini Alain , Honkimäki Veijo
Published: January 2012

Synchrotron X-ray diffraction is reliable to measure residual stresses and characterize existing phases close to substrate/coating interface. In the present study, we focus on the cobalt-alloys coating deposited on stainless steel forging tools via Plasma Transfer Arc (PTA) process. Forging tools always work in high temperature conditions. Since fatigue crack is often detected near to the interface, we used synchrotron radiation to characterize residual stress profiles both in the substrate and coating sides. Also, we defined phases inside diluted substrate layers and in the stellite coating using a Rietveld refinement.
On the Microstructure of Plate Steels for API-5L X120 Applications
Authors: Garcia C. Isaac , Hua Ming Jian , Liang X. , Suikannen P. , DeArdo Anthony J.
Published: January 2012

The very high strength now achievable in low carbon HSLA steel plates is caused by the formation of bainite or martensite during the post-hot rolling cooling in interrupted direct quenching. Modern electron optical examination, especially FEG-SEM, has allowed the microstructural features such as packet, block and lath dimensions and crystallography to be quantitatively determined. Several recent studies have attempted to relate the strength and toughness to these features, with limited success. However, one observation is clear, these microstructural features scale with the prior-austenite grain size and state of recrystallization. The role of microalloying, beyond grain refinement, remains inconclusive. This paper will discuss these microstructures and suggest possible ways of further refining them.
Time-Resolved X-Ray Diffraction Study on Solidification of Fe-B and Fe-C Eutectic Alloys
Authors: Mizuno Akitoshi , Tamura Jin , Kohara Shinji , Watanabe Masahito
Published: January 2012

Solidification processes of Fe-B and Fe-C eutectic alloys have been investigated by a time-resolved synchrotron x-ray diffraction under containerless cooling conditions using a conical nozzle levitation technique. To observe relative variations of structure from the undercooled liquid to crystalline phase, we have conducted millisecond order time-resolved x-ray diffraction experiments with a two-dimensional detector. The structural variations observed during the solidification of the Fe83C17 alloy were identified as the phase transformation process expected from the Fe-C phase diagram. As for the Fe83B17 alloy, it was revealed that a metastable phase composed of Fe23B6 compound was precipitated as a primary crystalline phase from the undercooled liquid. In addition, decomposition of the metastable Fe23B6 phase showed dependence on the cooling rate of the sample. At the cooling rate of 30 K/s, the Fe23B6 phase decomposed to bcc-Fe and Fe2B phases with decreasing temperature. On the contrary, at the cooling rate of 180 K/s, the metastable Fe23B6 phase remained in spite of an appearance of the bcc-Fe phase. By comparing the primary crystalline phase between the Fe83C17 and the Fe83B17 alloys, we suggest that the formability of the metastable Cr23C6-type compound is closely related with the glass-forming ability of Fe-metalloid binary alloys.
In Situ Gas Supply System on the Powder Diffraction Beamline I11 at Diamond Light Source
Authors: Parker J.E. , Potter J. , Thompson S.P. , Lennie A.R. , Tang C.C.
Published: January 2012

Beamline I11 at Diamond began accepting users for high resolution powder diffraction experiments in Oct 2008. We present the design, key specifications, performance and the hardware of this new beamline which receives an intense and highly collimated x-ray beam generated by an in-vacuum undulator. With the simple optics (a double-crystal monochromator, harmonic rejection mirrors and slits), a high purity beam of low energy-bandpass X-rays optimised at 15 keV is delivered at the sample. The heavy duty diffraction instrument is designed to have the flexibility to house a variety of sample environments and holds two detection systems to collect high quality diffraction data, i.e. multi-analysing crystals (MAC) for high angular resolution experiments and a fast position sensitive detector (PSD) for time-resolved studies. A recent addition to the beamline capabilities is the installation of a specifically designed gas control system. This allows the in-situ dosing of a powder sample with gases such as hydrogen and carbon dioxide, at low (~10 mbar) and high pressures (<100 bar). In addition a low pressure capillary sample cell is described which is now available to users of the beamline.
Ultra Fast In Situ X-Ray Micro-Tomography: Application to Solidification of Aluminium Alloys
Authors: Salvo Luc , Di Michiel Marco , Scheel Mario , Lhuissier Pierre , Mireux B. , Suéry Michel
Published: January 2012

X-ray micro-tomography has been applied recently in a wide range of research fields (damage in materials, solidification …). Thanks to the high flux of synchrotrons and specific cameras the total time to acquire a scan was considerably reduced. The use of a specific camera based on CMOS technology allows dividing the acquisition time for a complete scan by a factor of 100. Therefore we have been able to perform in situ solidification of aluminium-copper alloys at high cooling rates (between 1 and 10°C/s) and we will show results concerning the evolution of the microstructure in 3D in the early stage of solidification, in particular the morphology of the solid phase and the kinetics of growth.
Determination of Shearing Stresses (τxz and τyz) Using X-Ray Diffraction Method with Two-Dimensional Detector
Authors: Sasaki Toshihiko , Akita Junichi , Sone Yasutomo , Kobayashi Yuichi
Published: January 2012

Measurement of shearing stresses, τxz and τyz, by X-ray diffraction technique with two-dimensional detector was studied. The principle which was developed for an area detector type X-ray triaxial stress analysis was adopted for this purpose. In the present method, Debye ring was measured first and its whole part was used for determining shearing stresses. One Debye ring is enough to determine shearing stresses without accurate diffraction data such as lattice spacing in stress free. The result of the simulation showed that the present method is useful for the evaluation of shearing stresses by X-ray diffraction technique.
Hot Deformation of Cast and Extruded TiAl: An In Situ Diffraction Study
Authors: Schmoelzer Thomas , Liss Klaus Dieter , Mayer Svea , Yan Kun , Reid Mark , Dippenaar Rian J. , Peel Matthew J. , Clemens Helmut
Published: January 2012

Intermetallic TiAl alloys are a class of innovative high-temperature materials which are developed to replace the substantially denser Ni-base alloys in low-pressure turbine blades of jet engines. By streamlining the production process of these parts, a substantial decrease in production costs can be achieved. To this end, a profound knowledge of the microstructural processes occurring during hot deformation is a prerequisite. To investigate the microstructural development during forming operations, cast and extruded as well as only cast specimens were hot-deformed and the microstructural development investigated in-situ by means of a novel diffraction method. This powder diffraction method utilizes the behavior of individual reflection spots on the Debye-Scherrer rings for deriving the materials response to the deformation imposed. It was found that the behavior of the two specimens is rather similar, although the starting microstructures show pronounced differences.
Optimising Sintering in Metal Injection Moulding Using In Situ Neutron Diffraction
Authors: Goossens D.J. , Whitfield R.E. , Studer A.J.
Published: January 2012

The phase evolution during the sintering of metal injection moulded stainless steel, 316Land 17-4PH, has been observed using in situ neutron diffraction and Rietveld analysis. The formationof the ferrite phase in the final product is associated with the production of -ferrite at high temperatures.Coexistence of phases at high temperature is thought to allow the segregation of alloyingelements, stabilising the ferrite to lower temperature. To prevent ferrite in the final products the sinteringmust occur at a lower temperature than that at which -ferrite is formed. An alternative regimeis proposed in which the temperature would be cycled around the formation temperature of -ferrite.
Study of Fragment Behavior during Columnar-Equiaxed Transition of Hypoeutectic Alloy with Synchrotron Radiation
Authors: Zhang Jiao , Dong Qing , Dai Yong Bing , Sun Bao De , Xie Hong Lan
Published: January 2012

In the present work, solidification of hypoeutectic, eutectic and hypereutectic Al-Cu alloys was illustrated by synchrotron X ray imaging, and the CET of hypoeutectic alloy was picked out to thorough investigated. The mechanism of hypoeutectic dendrites fragment behaviors among the nucleation area was studied by in-situ imaging and first-principles computation. The results show that the density difference between the fragments and the enriched melt leads to the movement of the fragments. The ejected fragments contributed to the columnar-eutectic transition and expanded the breadth of mush zone in front of the solid/liquid interface.
Simulation on Nanostructured Metals Based on Multiscale Crystal Plasticity Considering Effect of Grain Boundary
Authors: Aoyagi Yoshiteru , Shimokawa Tomotsugu , Shizawa Kazuyuki , Kaji Yoshiyuki
Published: January 2012

Ultrafine-grained metals whose grain size is less than one micron have attracted interest as high strength materials. Whereas nanostructured metals produced by severe plastic deformation express remarkably peculiar behavior in both material and mechanical aspects, its mechanism has been clarified by neither experimental nor computational approaches. In this study, we develop a multiscale crystal plasticity model considering an effect of grain boundary. In order to express release of dislocation from grain boundaries, information of misorientation is introduced into a hardening law of crystal plasticity. In addition, carrying out FE simulation for FCC polycrystal, the stress-strain responses such as increase of yield stress due to existence of grain boundary are discussed. We investigate comprehensively the effect of dislocation behavior on the material property of nanostructured metal.
Microstructure Evolution during the Accumulative Roll Bonding Process in Armco Iron
Authors: Bonnot Erell , Brisset François , Helbert Anne Laure , Baudin Thierry
Published: January 2012

The Armco iron is one of the purest commercial iron with very low levels of carbon, oxygen and nitrogen. In order to improve the mechanical properties, it is worth applying severe plastic deformation to obtain ultrafine-grained bulk materials, with grain size lower than 1 μm. In this study, samples of Armco iron were subjected to a technique of severe plastic deformation named Accumulative Roll Bonding (ARB). This method consists in rolling to 50% two sheets pack of which the stacked surfaces were initially cleaned. Then, the rolled strip is sectioned in two halves, cleaned and stacked again and the procedure of roll-bonding repeated. Practically, the process can be repeated without limits. The important parameter of ARB is the number of cycles and then the consequent number of layers of the final sample. By means of the Electron Backscattered Diffraction (EBSD) technique, the evolution of both microstructure and texture as regard to the number of ARB cycles was studied. The analysis of mean grains size and high angle grain boundaries (HAGB) fraction as a function of the number of cycles showed an early formation of a subgrained structure with low angle boundaries and then the evolution of the microstructure towards an ultrafine-grained structure with an increase of HAGB.
Grain Refinement and Superplastic Deformation Behavior of Zn-Al Alloy
Authors: Kim Keun Joon , Na Gil Hwan , Ha Tae Kwon
Published: January 2012

Grain refinement and superplastic deformation behavior of Zn-Al alloys were investigated in this study. To obtain fine grain size in Zn-0.3Al alloys, rolling and equal channel angular pressing (ECAP) were conducted at temperatures from 40 to 160°C after casting and homogenization heat treatment. Material processing maps for Zn-0.3Al alloy were constructed from a series of compression tests conducted at temperatures from RT to 200°C and strain rates from 3×10-2 to 101 s-1. Superplasticity of ECAPed specimens were evaluated at the temperature of 100°C under the strain rate of 2×10-4 s-1. After ECAP of the Zn-0.3Al alloy, elongation was dramatically increased up to 500%. The effects of ECAP on the texture and anisotropy in the superplastic deformation bebavior were found to be negligible.
Experimental and Computational Studies of Competitive Precipitation Behavior Observed in Microstructures with High Dislocation Density and Ultra-Fine Grains
Authors: Masuda Tetsuya , Shoichi Hirosawa , Horita Z. , Matsuda Kenji
Published: January 2012

The competitive precipitation behavior observed in microstructures with high dislocation density and ultra-fine grains has been studied experimentally and computationally for cold-rolled and severe plastic deformed Al-Mg-Si alloy. The age-hardenability at 443K was reduced by the two deformation processes due to the accelerated formation of larger precipitates on dislocations and grain boundaries, in place of the transgranular precipitation of refined β” in the matrix. The developed numerical model based on the classical heterogeneous nucleation theory clarified the dislocation density and grain size dependences of the volume fraction of precipitates nucleated at different sites, in good agreement with experimental results. It could be therefore possible that three strengthening mechanisms of strain hardening, hardening by grain refinement and precipitation hardening are optimally exploited according to the computationally estimated dependences.
Enhanced Low-Temperature Impact Toughness of Ultra-Fine Grained SiCp/ZL108 Composites
Authors: Jiang Jing Hua , Ma Aibin , Wu Ying , Song Dan , An Sheng Hui , Zhang Wu Wen , Yang Dong Hui , Chen Jian Qing
Published: January 2012

A new strategy for increasing the low-temperature toughness of structural materials is in urgent need for overcoming the general rheotropic brittleness in coarse-grain state. Here, a unique phenomenon was observed that ultra-fine-grained (UFG) SiCp/ZL108 composites after severe plastic deformation (SPD) exhibit higher impact toughness at temperatures slightly lower than room temperature. The enhanced impact toughness is attributed to the simultaneous increase of strength and ductility of UFG materials at lower temperatures, related to grains or grain fragment boundary modification. This result demonstrates the advantage of fabricating UFG materials by SPD method and spurs the interest to use UFG materials in low-temperature conditions.
Strengthening of Alloys with Elastic Anisotropy by Severe Plastic Deformation
Authors: Kuramoto Shigeru , Furuta Tadahiko , Nagasako Naoyuki , Horita Z.
Published: January 2012

Effects of the elastic anisotropy on deformation behavior are examined in a Ti-23%Nb-0.7%Ta-2%Zr-1.2%O (in at %) alloy, Gum Metal, and in an Fe-19%Ni-34%Co-8%Ti alloy with body centered cubic (bcc) crystal structure, and microstructural development in the iron based alloy during severe plastic deformation (SPD) process is discussed. Strong elastic anisotropy with reduced shear modulus, C11- C12, results in low ideal shear strength, which implies dislocation mediated plasticity easily occurs at lower stress. On the other hand, high pressure torsion (HPT), a typical SPD method, realizes very high shear stress during processing, which seems to reach the ideal shear strength in these alloys. Significant refinement of the grain size to 20 - 50 nm in the Fe-Ni-Co-Ti alloy is discussed in relation to the unique deformation mechanism which might be activated at ideal shear strength.
Developing Hardness and Microstructural Homogeneity in High-Pressure Torsion
Authors: Kawasaki Megumi , Langdon Terence G.
Published: January 2012

High-pressure torsion (HPT) is a processing technique in which samples, in the form of thin disks, are subjected to a high applied pressure and concurrent torsional straining. In principle, the strain introduced into the disk during the straining varies across the disk and there is a direct proportionality between the estimated strain and the radial position on the disk. This means that the strain is zero at the center of each HPT disk and it reaches a maximum value at the outer periphery. Contrary to these expectations, recent experiments show there is a gradual evolution with increasing numbers of revolutions such that the hardness of the disk gradually becomes reasonably homogeneous. This report examines the development of hardness and microstructural homogeneity with special emphasis on the evolution in hardness homogeneity along vertical sections of disks of high-purity aluminum processed by HPT. The results demonstrate that, at least for pure aluminum, the distributions in the hardness values are independent of the plane of sectioning.
Influence of Alloying Elements on the Hall-Petch Coefficient in Ferritic Steel
Authors: Takaki Setsuo
Published: January 2012

Yield strength of ferritic steel increases with grain refinement standing on the Hall-Petch relation. In low carbon ferritic steels, the following relation is established between yield strength σy and grain size d: σy [MPa]= 100+600/√d [μm]. The Hall-Petch coefficient of interstitial free steels is substantially small as 0.15MPa·√m but it can be greatly increased by the existence of small amount of solute carbon less than 60ppm. As for the effect of substitutional elements such as Cr and P, some papers reports fairly large influence to the Hall-Petch coefficient of ferritic iron. However, the effect of small amount of carbon is sometime neglected or not cleared on the evaluation of Hall-Petch coefficient in ferritic steels. In order to evaluate the effect of substitutional elements, the research should be performed using interstitial free steels to eliminate the influence of solute carbon and nitrogen. In this paper, Hall-Petch relation was examined in iron, Fe-Cr alloys and Fe-P alloys with 0.02-0.05mass% Ti and the following results were obtained: 1) The Hall-Petch coefficient of interstitial free iron is about 0.15MPa·√m. 2) Chromium does not give any influence to the Hall-Petch coefficient of ferritic iron, although the friction stress σ0 is enhanced in proportional to chromium content (Δσ0 [MPa]=7×(mass%Cr)). 3) Phosphorus does not affect the Hall-Petch coefficient of ferritic iron or reduce it somewhat but increases markedly the friction stress σ0 (Δσ0 [MPa]=250×(mass%P)1/2). 4) Even under the co-existence of carbon with chromium and phosphorus, carbon dominantly works to increase the Hall-Petch coefficient of ferritic steels, but it is changeable due to the interaction between carbon and the other substitutional elements.
Equal Channel Angular Pressing of Cu-Al Bimetallic Rod
Authors: Llorca-Isern Nuria , Escobar Romero Ana Maria , Roca Antoni , Cabrera Jose María
Published: January 2012

Coextrusion and corolling are the major processes to produce bimetallic rods, tubes and wires, the objective being to perform clad metals, bimetallic joints or seals. The aim of the present work is to produce bimetallic rods showing an ultrafine grained microstructure with enhanced properties. Bimetallic Cu-Al rods were deformed by equal channel angular pressing (ECAP) in order to study their microstructure. ECAP is an interesting process for producing bulk materials with refined microstructure and, consequently, changes in physical, chemical and mechanical properties can be observed. Higher shear strength and dimensional stability are among the advantages of this process. A comparative experimental study of pure commercial copper with cylindrical inner aluminium rods of different diameters processed by one-pass equal channel angular pressing has been carried out. The ECAP die used in this research was a 90º 2-channels intersecting angle. Electron backscattered (EBSD) and X-ray diffraction techniques were used for microstructure characterization (deformation, grain fragmentation and microstrain evaluation) at the interfaces and away from them. It was found that the microstructure in the ECAP deformed Cu-Al bimetallic rods was influenced by the dimensions of the aluminium inner rod. In fact, the microstructure appeared to be much more elongated and refined in the samples containing smaller diameter aluminium rods.
Effect of Annealing on the Microstructure, Texture and Mechanical Properties of Severely Deformed Interstitial Free Steel
Authors: Hazra Sujoy S. , Gazder Azdiar , Pereloma Elena V.
Published: January 2012

Ti-stabilised interstitial free (IF) steel initially subjected to 8 passes, route BC equal channel angular pressing (ECAP) was further cold rolled (CR) at room temperature to 95% thickness reduction. Both samples were isothermally annealed at 710 °C following which their microstructures and micro-textures were compared via electron back-scattering diffraction (EBSD). The mechanical properties first obtained by shear punch testing (SPT) were later corroborated by uniaxial tensile tests. In the case of the ECAP material, continuous recrystallisation is followed by abnormal growth at prolonged annealing times with minor increases in high angle boundary (HAGB) fraction. On the other hand, the additionally CR material shows continuous recrystallisation accompanied by a reduction in the HAGB fraction. After 15 s annealing, the ECAP and CR samples exhibit a good strength-ductility balance; which corresponds to ~52% and ~67% softening, respectively.
Friction Stir Processing of the Magnesium Alloy AZ61: Grain Size Refinement and Mechanical Properties
Authors: del Valle J.A. , Rey P. , Gesto D. , Verdera D. , Ruano Oscar
Published: January 2012

The effect of friction stir processing (FSP), on the microstructure and mechanical properties of a magnesium alloy AZ61 has been analyzed. This is a widely used wrought magnesium alloy provided in the form of rolled and annealed sheets with a grain size of 45 μm. The FSP was performed with an adequate cooling device in order to increase the heat extraction and reduce the processing temperature. The final microstructure showed a noticeable grain size refinement down to values close to 1.8 μm and an important change in texture. The change in texture favors basal slip during tensile testing leading to an increase of ductility and a decrease in yield stress. The stability of the grain size and the creep behavior at high temperatures were investigated. The optimum conditions for superplastic forming were determined; however, the presence of a large amount of cavities precludes the achievement of high superplastic elongations. Additionally, these results are compared with those obtained by severe hot rolling.
Crystallographic Features of Martensite Transformed from Ultrafine Grained Austenite Fabricated by Severe Plastic Deformation
Authors: Shibata Akinobu , Jafarian Hamidreza , Terada Daisuke , Tsuji Nobuhiro
Published: January 2012

We studied the crystallographic features, especially the orientation relationship with respect to austenite, of martensite in a steel transformed from coarse-grained equiaxed austenite (35 μm), ultrafine-grained equiaxed (2.5 μm) or lamellar (300nm) austenite fabricated by sever plastic deformation. With decreasing the grain size of equiaxed austenite, the orientation relationship changed from Kurdjumov - Sachs relationship to Greninger - Troiano relationship. We inferred that this change of orientation relationship could be attributed to the small size of martensite plate transformed from the ultrafine-grained equiaxed austenite. The martensite transformed from the ultrafine-grained lamellar austenite did not have a definite orientation relationship with austenite. We considered that a high density of dislocations or a high density of low angle boundaries within the ultrafine lamellar austenite grain resulted in the large deviation of orientation relationship.
Microstructural and Mechanical Properties of UFG Silver Subjected to Severe Plastic Deformation by ECAP
Authors: Angella Giuliano , Bassani Paola , Farè Stefano , Lecis Nora , Ripamonti Dario , Spagnoli Fabio , Tuissi Ausonio , Vedani Maurizio
Published: January 2012

The present contribution is aimed at investigating the microstructure evolution of commercially pure silver under severe plastic deformation conditions. ECAP billets have been produced by using a die with channels intersecting at 90° and straining the samples at room temperature. The evolution of the microstructure as a function of imparted strain was evaluated by scanning electron microscopy as well as X-ray diffractometry. Furthermore, tensile properties were measured from ECAP billets in order to evaluate the strengthening and work hardening behaviour of silver as a function of structure evolution. Comparison in terms of grain structure and corresponding properties are also drawn by considering published data about Al-Mg-Si alloy samples ECAP-processed by identical routes and parameters.
Mechanical Properties of Ultrafine Grained Two-Phase Titanium Alloy Produced by “abc” Deformation
Authors: Zherebtsov Sergey V. , Kostjuchenko Sergey , Kudryavtsev Egor A. , Malysheva Svetlana , Murzinova Maria A. , Salishchev Gennady A.
Published: January 2012

The mechanical properties of two-phase Ti-6Al-4V titanium alloy with ultrafine grained microstructure were studied in the present work. Bulk ultrafine grained specimens of the alloy were produced by means of warm “abc” deformation. The final structure consisted of α/β particles with a size of 500 nm. Extensive studies of the mechanical properties of this material in comparison with conventionally heat-strengthened condition were conducted. A room-temperature strength and fatigue resistance of the ultrafine grained material was found to be 25-40% higher than that of heat-strengthened alloy. However such ductility related properties as tensile elongation and impact toughness noticeably decreased with decreasing grain size. Efficacy of ductility improvement and the strength/ductility balance optimization were analyzed.
DC Casting, Deformation and Strengthening of Al-Si Alloys
Authors: Zuo Liang , Yu Fu Xiao
Published: January 2012

Al-Si alloys are widely used as cast alloys for their excellent castability, low thermal expansion coefficient, good wear resistance and corrosion resistance properties. However, the poor ductility of these alloys, caused by the presence of coarse and non-deformable Si phase in the as-cast state, has inhibited their applications as wrought materials. Recently, a process based on traditional technologies, i.e., direct chill (DC) casting followed by hot deformation and heat treatment, has been developed for potential mass production of wrought Al-Si alloys with superior mechanical properties in view of their strength and ductility. In this work, the microstructural evolutions of DC cast Al-Si alloys involved in solidification, recrystallization and precipitation during the processing are highlighted, aiming at understanding the correlations between the microstructures and the mechanical properties.
Ultrafine Grain Structure Evolution in AA6085 Aluminium Alloy Processed by HPT at Increased Temperature
Authors: Zrník Jozef , Kraus Libor , Scheriau Stephan , Pippan Reinhard
Published: January 2012

In this study ultrafine grain structure evolution during high pressure torsion (HPT) of commercial aluminium alloy AA6082 at increased temperature is presented. Two different initial structural states of the alloy were prepared by thermal treatment. The progress in structure refinement in dependence on the shear strain level strain was investigated by TEM of thin foils. The impact of different amount of strain (εef) introduced was analyzed with respect to the effect of increased temperature. The microhardness results measured across the deformed discs pointed out that some data scattering. The results of microstructure analyses showed that ultrafine grain (ufg) structure was already formed in deformed disc upon the first turn, regardless the initial structure of alloy, resulting from prior thermal treatment. The observed heterogeneity in ufg structure formation across the deformed disc was observed, supporting microhardness results scattering. By increasing the strain level (number of turns N-2,4,6), more effectively homogenized ufg structure was observed across the deformed discs. The effect of increased deformation temperature became evident and dynamic recrystalization modified locally ufg structure.. The retardation of new grains growth and higher thermal stability of ufg structure was observed, when two steps thermal treatment of alloy (quenching and ageing) was executed prior deformation. Strength measurements results yielded form tensile tests showed that the effect of structure strengthening was degraded by local recrystallization. The results of torque measurement versus the time showed that the torque required to deform the sample was increasing until the first turn and then kept stable or even decreased.
Shielding Effectiveness of CNTs/SSFs/PA6 Conductive Composites
Authors: Zhang Yang Fei , Luo Yang , Bai Shu-Lin , Li Man , Jia Zhi Yong
Published: January 2012

A series of carbon nanotube (CNTs) and stainless steel fiber (SSFs) filled nylon 6 (PA6) conductive composites were synthesized for electromagnetic interference (EMI) shielding applications. The materials were prepared by the melt blending method with CNTs weight fraction of 1 and 3 wt% and SSFs of 2, 4, 6, 8, 10, and 12 wt%. The shielding effectiveness, electrical resistance and crystallization behaviors were measured. The results indicate that the shielding effectiveness and electrical properties can be improved by increasing either SSFs or CNTs contents. Higher content of CNTs can bring forward the percolation threshold and enhance the shielding effectiveness to 51.8 dB. Due to the nanoconfinement/multiple nucleation effects, PA6 crystallization behavior is influenced by adding the CNTs and SSFs.
Application of EBSD to the Crystallographic Investigation on Ni-Mn-Ga Alloys
Authors: Li Zong Bin , Zhang Yu Dong , Esling Claude , Yang Hao , Wang Ji Jie , He Chang Shu , Zhao Xiang , Zuo Liang
Published: January 2012

For off-stoichiometric Ni2MnGa ferromagnetic shape memory alloys, a large shape change could be induced through the rearrangement of martensitic variants under an external magnetic field. Insight into the orientation relationships of martensitic variants and the characteristics of variant boundaries is thus essential for understanding the magnetic shape memory performance. In this paper, a thorough crystallographic investigation was made on the incommensurate 7M modulated martensite in one polycrystalline Ni50Mn30Ga20 alloy by means of X-ray diffraction and SEM electron backscattered diffraction (EBSD). Locally, there are four differently-oriented martensitic variants, being twin related to one another. The twin interface planes are coherent and they are in coincidence with the respective twinning planes (K1). A primary exploration was performed to improve the microstructure by repeated magnetic field training during phase transition. The present investigation could offer useful guidance to develop specific technique for microstructure optimization.
Elaboration of Architectured Materials by Spark Plasma Sintering
Authors: Fabrègue Damien , Mouawad Bassem , Buttay Cyril , Soueidan Maher , Lamontagne Aude , Forte Romain , Perez Michel , Courtois Loic , Landron Caroline , Maire Éric , Massardier-Jourdan Véronique
Published: January 2012

Spark plasma sintering has been used for decades in order to consolidate a wide variety of materials and permitting to obtain fully dense specimens. This technique has been mainly applied to ceramics. This paper concentrates on an unusual use of spark plasma sintering system: obtaining innovative materials especially architectured ones. Different applications are presented. Firstly, the SPS technique has been used to elaborate nanometers grain size materials or containing nanoscale microstructure. This is possible since the sintering temperature and the holding time are far lower in the SPS compared to other techniques. Then SPS has been used to realize diffusion bonding. In that case again, bonding can be realized at low temperature and for short time. It permits for example to realize bonding between two copper layers which is of a great importance for microelectronic applications. It is worth noting that this bonding can have the same mechanical strength as pure copper even for diffusion time of a few minutes. Secondly, bonding has been also carried out between a metallic layer and a ceramic one. This could lead to design of new layered materials combining interesting properties in terms of mechanical strength but also in terms of electrical resistance. The SPS machine has also been used to obtain porous materials (cobalt alloys or copper) with an adapted microstructure (porosity, tortuosity,). These structures could open new perspectives for biomedical or for microelectronic applications. All these examples lead to a better understanding of the physical processes which happen during spark plasma sintering.
Influence of Fe Content of Ti-Mn-Fe Alloys on Phase Constitution and Heat Treatment Behavior
Authors: Ikeda Masahiko , Ueda Masato , Kinoshita Takahiro , Ogawa Michiharu , Niinomi Mitsuo
Published: January 2012

If Mn could be partly substituted by Fe, Ti-Mn-Fe alloys would be less costly than Ti-Mn alloys. Furthermore, the use of iron as a beta-stabilizing element is more suitable than the use of manganese from a situation of an element strategy. In this study, 4.26 was admitted as the average ratio of valence electrons to atoms, e/a. The compositions of Mn and Fe were chosen under 4.26 as e/a. We investigated the influence Fe in selected Ti-Mn-Fe alloys by performing electrical resistivity, Vickers hardness, and X-ray diffraction measurements. In solution-treated and water-quenched 10Mn alloy, the beta and athermal omega phases were identified, while only the beta phase was identified in 8.7Mn-1Fe, 6.1Mn-3Fe, and 3.5Mn-5Fe alloys. In all alloys, equiaxial beta grains were observed by optical microscope. The resistivities at room and liquid-nitrogen temperatures and the Vickers hardness were relatively invariant across all Ti-Mn-Fe alloys, except for the Vickers hardness of the 5Fe alloy. During aging at 773 K, an isothermal omega phase precipitated in only the 3.5Mn-5Fe alloy, whereas only the alpha phase precipitated in the others.
Effect of Substrate Temperature on the Shape Memory Behavior of Ti-Ni-Cu Ternary Alloy Sputtered Films
Authors: Inoue Shozo , Morino K. , Yoshiki Keisuke , Namazu Takahiro
Published: January 2012

The purpose of this work is to establish a deposition process of Ti-Ni-Cu films showing shape memory effect in the as-deposited state. 5-µm-thick Ti50Ni35Cu15 films have been deposited onto thermally oxidized (001) Si wafer by triple-source dc magnetron sputtering at various substrate temperatures. Their shape memory behavior were characterized by XRD, DSC measurements and thermal cycling tests under various constant tensile stresses. We have confirmed that crystalline films can be grown directly when the substrate temperature exceeds 400°C. The films deposited at higher than 450°C showed thermoelastic martensitic transformation and their Ms temperature slightly increased with increasing substrate temperature. Since their Ms temperature were found to be higher than 30°C, they can be used as an actuator at RT. These films were also found to have higher critical stress against plastic deformation than the post-deposition crystallized films. We have also tried to fabricate a prototype of micro-actuator and to characterize their actuation behavior and have confirmed that TiNiCu/SiO2 double layered diaphragm showed an actuation response to a pulsed current of more than 100Hz.
Mechanical Properties of Hot-Pressed Compacts Made by Alumina Particle Dispersion Magnesium Powders
Authors: Kawamori Shigehiro , Kuroda Kiyoshi , Hiroshi Fujiwara , Ameyama Kei
Published: January 2012

To enhance the mechanical properties of Mg alloys, powders of pure Mg (Al2O3/Mg) dispersed with over 10 vol% Al2O3 particles were formed by ball milling powder mixtures of pure Mg and Al2O3 particles with particle sizes of 0.3 and 1 μm. The effect of the Al2O3 content of hot-pressed discs of Al2O3/Mg powders on the mechanical properties was investigated. The hardness increased sharply at certain Al2O3 content. This is considered to be because of the development of Al2O3 particle strengthening due to the excellent interfacial bonding between Mg and Al2O3 particles when the Al2O3/Mg discs contain a sufficient amount of Al2O3 particles and have a sufficient interparticle distance. The maximum hardness was 220 HV. The tensile strength increased as Al2O3 content was increased. The Al2O3/Mg plate with Al2O3 particles sizes of 0.3 and 1 μm indicated maximum values of the bending strength at 10 and 14vol%Al2O3 content, respectively.
A Comparative Study of Structure Formation in Thermomechanically Treated Ti-Ni and Ti-Nb-(Zr, Ta) SMA
Authors: Prokoshkin Sergey , Brailovski Vladimir , Inaekyan Karine , Korotitskiy Andrey , Dubinskiy Sergey , Filonov Mikhail R. , Petrzhik Mikhail
Published: January 2012

The processes of structure formation in Ti-Ni and in Ti-Nb-Zr, Ti-Nb-Ta shape memory alloys (SMA) under thermomechanical treatment (TMT) were studied. The TMT comprised cold rolling with true strains from e=0.25 to 2 and post-deformation annealing. Differences in these processes between two groups of alloys are considered. The main conclusions are as follows: nanostructures created by TMT are useful for radical improvement of the SMA functional properties, and an optimum nanostructure (nanocrystalline structure, nanosubgrained structure or theirmixture) should be selected by taking into account other structural and technological factors.
Application of Digital Image Correlation (DIC) on Magnetostriction of Fe-Pd Alloy
Authors: Chiue Juang Yu , Lin Hung Pin , Kuo Jui Chao
Published: January 2012

In this study, the relationship between magnetostriction and microstructure for a Fe-30at-%Pd alloy was investigated. The alloy was fabricated by vacuum arc melting, followed by 24 h annealing under vacuum at 1000 °C and then by quenching in ice water. Crystal structure, orientation mapping, and phase identification were obtained by employing X-ray diffraction and electron back-scatter diffraction. Magnetic properties were measured using vibrating sample magnetometer. Magnetostriction of a Fe-30at-%Pd alloy was obtained using the digital image correlation technique under different magnetic fields. The maximum strain of Fe-30at-%Pd alloy was 5×10-4 at a magnetic field of 7500 Oe.
Friction Stir Processing (FSP) of Cast Metals: Processing - Microstructure - Property Relationships
Authors: McNelley Terry R. , Sarath Menon E.
Published: January 2012

FSP is an allied technology of friction stir welding (FSW). These processes are reviewed and the additional considerations such as processing pattern and step over distance in FSP are introduced. The application of FSP to cast metals including AA5083, Al-7Si and NiAl bronze is summarized. As-cast microstructures may be converted to a wrought condition in the absence of external shape change and the extent of grain refinement and homogenization of microstructure is documented. The FSP-induced superplastic response of AA5083, enhanced ductility of Al-7Si and surface hardening of NiAl bronze are summarized as examples of properties developed by FSP.
Fabrication of Ti-Sn-Cr Shape Memory Alloy by PM Process and its Properties
Authors: Ashida Sumio , Kyogoku H. , Hosoda Hideki
Published: January 2012

Ti-Sn-Cr shape memory alloys were fabricated by the powder metallurgy (PM) process. The mixed powders in composition of Ti-3at%Sn-7at%Cr were prepared using a V-blender. The mixed powders were filled into a graphite die, and then sintered at a temperature between 1023 K and 1223 K using a pulse current sintering equipment. The sintered alloy was solution-treated and then aged. The phase structure and the tensile properties of the alloy obtained were investigated. The relative density of the as-sintered alloy increased with elevating sintering temperature, and the maximum relative density was 99.5 % at a sintering temperature of 1223 K. Although the as-sintered alloy was high density, the microstructure of the alloy was inhomogeneous. Thus it was found that the solution treatment was needed to obtain the homogeneous microstructure of the alloy. The alloy which is mainly consisted of the β phase was obtained by performing solution treatment. The plateau region due to the slip deformation was observed in the stress-strain curve of the solution treated alloy, but that due to the stress induced martensite transformation could not be done. The plateau region due to the stress induced martensite transformation, however, was appeared in the stress-strain curve of the aged alloy. This means that the aged alloy has shape memory properties. It was also found from the result of bending test that the alloy fabricated by the PM process has obviously shape recovery properties.
Dynamic Molding of Powder Particles at Room Temperature
Authors: Miki Hiroyuki , Nakayama Noboru , Takeishi Hiroyuku
Published: January 2012

A new method of solidifying metal powder by dynamic molding under compression stress was developed. In the solidified specimen, recrystallization is suppressed, so that nanoscale crystal grains remain. The hardness of the specimen prepared by this process is increased relative to materials prepared by other methods. The material properties and preferred orientation of an aluminum plate with crystal grains 100−200 nm in diameter prepared by the new molding process are reported. The correlation between the crystal structure and properties of crystallization are clarified.
Metal Injection Molding of Super Elastic Ti Alloy Materials
Authors: Miura Hideshi , Kang Hyun Goo , Sagara Kensaku
Published: January 2012

Ti-10V-2Fe-3Al is one of super elastic Ti alloys, which is the b type Ti alloy and shows the excellent properties such as high specific strength and corrosion resistance. By the combination of Cold working and heat treatment, high strength as same as the steels are obtained. Therefore, Ti-10V-2Fe-3Al is hoped to be a next generation’s spring material. In this study, Metal Injection Molding of super elastic Ti alloy materials are investigated by changing the process parameters such as powder type (mixed elemental or alloy), debinding and sintering conditions, and heat treatment conditions to obtain the excellent super elastic properties. Tensile strength of injection molded Ti-10V-2Fe-3Al compacts sintered at 1250 with mixed elemental powders showed approximately 85% of wrought materials. On the other hand, alloy powder compacts showed about 80% strength of wrought materials. Their super elastic behavior depended strongly on the heat treatment conditions.
Thermal Properties of Al/Diamond Composites Fabricated in Continuous Solid-Liquid Co-Existent State by SPS
Authors: Mizuuchi Kiyoshi , Inoue Kanryu , Agari Yasuyuki , Morisada Yoshiaki , Sugioka Masami , Tanaka Motohiro , Takeuchi Takashi , Tani Junichi , Kawahara Masakazu , Makino Y. , Ito Mikio
Published: January 2012

Diamond-particle-dispersed-aluminum (Al) matrix composites were fabricated in continuous solid-liquid co-existent state by spark plasma sintering (SPS) process from the mixture of diamond powders, pure Al powders and Al-5mass%Si alloy powders. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were well consolidated by heating at a temperature range between 798K and 876K for 1.56ks during SPS process. No reaction at the interface between the diamond particle and the Al matrix was observed by scanning electron microscopy for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the diamond-Al composite fabricated was 99% or higher in a volume fraction range of diamond between 45% and 50%. Thermal conductivity of the diamond-Al composite containing 50 vol.% diamond reached 552W/mK, approximately 95% the theoretical thermal conductivity estimated using Maxwell-Eucken’s equation.
Surface Modification of Cobalt Chrome Molybdenum Cast Alloy by Electron Beam Irradiation
Authors: Nagae Takekazu , Kakiuchi Shigeki , Yamagishi Hideki , Yamaguchi Emi , Yoneda Takashi , Tomida Shogo
Published: January 2012

We irradiated the surface of a Co-Cr-Mo cast alloy plate with an electron beam in order to increase the surface hardness. An accelerating voltage of 40 kV and a current of 1~10 mA of the irradiated electron beam were used. The irradiation time for a single dot was 0.1 ms and the distance between dots (dot pitch) was 0.2 mm, corresponding to a scanning speed of 200 mm/s. A fine cellular structure was obtained by irradiating a low current electron beam. When a high current electron beam (more than 8 mA) was used for the irradiation, fine granular carbides were synthesized. The Vickers hardness of the base metal of 410 HV was increased to about 480~530 HV by the electron beam irradiation.