The Experts below are selected from a list of 2010 Experts worldwide ranked by ideXlab platform
D L Chen - One of the best experts on this subject based on the ideXlab platform.
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effect of strain ratio on cyclic deformation behavior of a rare earth containing Extruded Magnesium alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: F.a. Mirza, D L Chen, X.q. ZengAbstract:Abstract Cyclic deformation characteristics of an Extruded Mg–10Gd–3Y–0.5Zr (GW103K) Magnesium alloy were determined via the strain-controlled low cycle fatigue tests with varying strain ratios at a constant strain amplitude. Unlike the rare-earth (RE)-free Extruded Magnesium alloys, the present alloy exhibited symmetrical hysteresis loops in tension and compression in the fully reversed strain-control tests at a strain ratio of R e =−1. This was due to the presence of relatively weak crystallographic textures and the suppression of twinning–detwinning activities arising from the fine grain sizes and RE-rich particles. At a strain ratio of R e =0 and 0.5, a large amount of plastic deformation occurred in the tensile phase of the first cycle of hysteresis loops due to the high positive mean strain values. With decreasing strain ratio, the hysteresis loops became wider. Fatigue life of this alloy was observed to be the longest in the fully reversed strain control at R e =−1, and it decreased as the strain ratio was deviated from R e =−1. A certain degree of mean stress relaxation was also observed in the non-fully reversed strain control (i.e., R e ≠−1 tests).
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Texture transformation in an Extruded Magnesium alloy under pressure
Materials Science and Engineering: A, 2013Co-Authors: D Sarker, D L ChenAbstract:Abstract Extruded AM30 Magnesium alloy showed two types of initial basal textures {0001}〈2110〉 and {0001}〈1010〉. Compressive deformation along extrusion direction resulted in their vanishing and the formation of {1210}〈0001〉 and {0110}〈0001〉 textures, indicating that the c-axes always rotated towards the anti-compression direction due to extension twinning.
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detwinning and strain hardening of an Extruded Magnesium alloy during compression
Scripta Materialia, 2012Co-Authors: D Sarker, D L ChenAbstract:The plastic deformation of an Extruded Mg–Al–Mn (AM30) Magnesium alloy in the extrusion direction by compression can be characterized by three distinct stages. Twinning was observed in stage A with a decreasing strain-hardening rate. Detwinning occurred due to strong twin–dislocation interactions in stage B, which was represented by an increasing strain-hardening rate over an extended strain range. Stage C with a decreasing strain-hardening rate was due to a reducing resistance of fewer twins to the dislocation slip.
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strain controlled low cycle fatigue properties of a newly developed Extruded Magnesium alloy
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2008Co-Authors: S Begum, D L Chen, S XuAbstract:To reduce fuel consumption and greenhouse gas emissions, Magnesium alloys are being considered for automotive and aerospace applications due to their low density, high specific strength and stiffness, and other attractive traits. Structural applications of Magnesium components require low-cycle fatigue (LCF) behavior, since cyclic loading or thermal stresses are often encountered. The aim of this article was to study the cyclic deformation characteristics and evaluate LCF behavior of a recently developed AM30 Extruded Magnesium alloy. This alloy exhibited a strong cyclic hardening characteristic, with a cyclic strain-hardening exponent of 0.33 compared to the monotonic strain-hardening exponent of 0.15. With increasing total strain amplitude, both plastic strain amplitude and mean stress increased and fatigue life decreased. A significant difference between the tensile and compressive yield stresses occurred, leading to asymmetric hysteresis loops at high strain amplitudes due to twinning in compression and subsequent detwinning in tension. A noticeable change in the modulus was observed due to the pseudoelastic behavior of this alloy. The Coffin–Manson law and Basquin equation could be used to describe the fatigue life. At low strain ratios the alloy showed strong cyclic hardening, which became less significant as the strain ratio increased. The lower the strain ratio, the lower the stress amplitude and mean stress but the higher the plastic strain amplitude, corresponding to a longer fatigue life. Fatigue life also increased with increasing strain rate. Fatigue crack initiation occurred from the specimen surface and crack propagation was mainly characterized by striation-like features. Multiple initiation sites at the specimen surface were observed at higher strain amplitudes.
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strain hardening and strain rate sensitivity of an Extruded Magnesium alloy
Journal of Materials Engineering and Performance, 2008Co-Authors: D L ChenAbstract:The strain-hardening behavior and strain-rate sensitivity of an Extruded AZ31B Magnesium alloy were determined at different strain rates between 10−2 and 10−5 s−1 in relation to the thickness of specimens (2.5 and 4.5 mm). Both the common approach and Lindholm’s approach were used to evaluate the strain-rate sensitivity. The yield strength (YS) and the ultimate tensile strength (UTS) increased, the ductility decreased, and the brittle fracture characteristics increased with increasing strain rate. The thinner specimens exhibited a slightly higher UTS, lower ductility, higher strain-hardening exponent, and strain-hardening rate due to smaller grain sizes. The stage III strain-hardening rate linearly decreased with increasing true stress, but increased with increasing strain rate. In comparison to the common approach, the Lindholm’s approach was observed to be more sensitive in characterizing the strain-rate sensitivity due to larger values obtained. The thinner specimens also exhibited higher strain-rate sensitivity. As the true strain increased, the strain-rate sensitivity decreased.
Walter Reimers - One of the best experts on this subject based on the ideXlab platform.
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Characterization of weld seam properties of Extruded Magnesium hollow profiles
Journal of Materials Science, 2016Co-Authors: Felix Gensch, Sven Gall, Sören Müller, Christoph Fahrenson, Walter ReimersAbstract:Extrusions of hollow profiles with weld seams were conducted using the Magnesium alloy ME21 applying various extrusion ratios. Subsequent analysis of the profiles’ microstructure was performed comparing weld free with weld seam containing material using (polarized) light optical microscopy (LOM). Additionally, the local texture and microstructure in the weld-free material as well as in the weld seam region has been examined with a scanning electron microscope coupled with electron backscatter diffraction technique (SEM-EBSD). The weld-free material and the weld seam are characterized by recrystallized microstructures, whereas few residual cast grains were identified. The local texture distinctively changes from the weld-free material to the weld seam. The texture of the weld-free material is comparable with the typical ME21 sheet texture. In the weld seam area, a pole density is found, which is distributed towards the transverse direction (TD) combined with a split and broadening of the pole density in the extrusion direction (ED). This texture influences the mechanical anisotropy due to the dependence of the activation of basal 〈a〉-slip and $$ \{ 10\bar{1}2\} \;\langle 10\bar{1}1\rangle $$ { 10 1 ¯ 2 } ⟨ 10 1 ¯ 1 ⟩ -extension twinning on the loading direction in favorably oriented grains.
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The effect of heat treatments on the microstructure, texture and mechanical properties of the Extruded Magnesium alloy ME21
International Journal of Materials Research, 2011Co-Authors: Katrin Brömmelhoff, Michael Huppmann, Walter ReimersAbstract:Abstract Heat treatments of the hot Extruded Magnesium alloy ME21 were performed at 400 °C – 550 °C and various annealing times. The evolution of the microstructure, the texture and the resulting m...
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Analyses of deformation twinning in the Extruded Magnesium alloy AZ31 after compressive and cyclic loading
Journal of Materials Science, 2011Co-Authors: Michael Huppmann, Martin Lentz, Sarkis Chedid, Walter ReimersAbstract:The influence of different loading conditions on the microstructural development of Extruded Magnesium alloy AZ31 was investigated by optical microscopy and electron backscattered diffraction. Extruded Magnesium profiles exhibit a significant asymmetry in the mechanical properties, due to the low activation energy of the extension twinning system $$ \left\{ {10\overline{1} 2} \right\}\langle {10\overline{1} 1}\rangle,$$ when compressing along the extrusion direction. For the analyses of this twinning system, compression tests with different applied strains 0.4 ≤ ε ≤ 11% were performed for two extrusion products exhibiting different microstructures. The main deformation mechanisms during cyclic loading are the formation of extension twins during compression and the detwinning during subsequent tensile loading. The strain-controlled fatigue tests were carried out with applied strain amplitudes 0.3 ≤ ε_A ≤ 5%. The tests were stopped at characteristic numbers of cycles N in the tensile or compression maximum of the hysteresis loop. The microstructural investigations deliver information about the type of twinning and the size, shape, local distribution, and volume fraction of twins as a function of the plastic deformation. These results will be discussed with regard to the microstructure of the initial state material and to the applied load.
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Microstructural development of the hot Extruded Magnesium alloy AZ31 under cyclic testing conditions
International Journal of Materials Research, 2010Co-Authors: Michael Huppmann, Sebastian Stark, Walter ReimersAbstract:Abstract A study of the internal strain (stress) evolution during uni-axial cyclic deformation along the prior extrusion axis with fully reversed total constant strain amplitudes eA (0.5% < eA < 5%) was investigated by using in-situ high energy synchrotron X-ray diffraction. The deformation is dominated by {1012} 〈1011〉 twinning and detwinning mechanisms within the textured hot Extruded Magnesium alloy AZ31. The results show a strong load partitioning between the internal stresses of (1010) and (1120) parent grains and of the (0002) twinned daughter grains that are relaxed. Following the evolution of the twinning/detwinning behavior and the hkil dependent microstresses as a function of cycling numbers, two different regimes were observed whereby it was found that the transition between these regimes is marked by an applied strain amplitude of eA = 0.625%.
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Analyses of deformation twinning in the Extruded Magnesium alloy AZ31 after compressive and cyclic loading
Journal of Materials Science, 2010Co-Authors: Michael Huppmann, Martin Lentz, Sarkis Chedid, Walter ReimersAbstract:The influence of different loading conditions on the microstructural development of Extruded Magnesium alloy AZ31 was investigated by optical microscopy and electron backscattered diffraction. Extruded Magnesium profiles exhibit a significant asymmetry in the mechanical properties, due to the low activation energy of the extension twinning system \( \left\{ {10\overline{1} 2} \right\}\langle {10\overline{1} 1}\rangle,\) when compressing along the extrusion direction. For the analyses of this twinning system, compression tests with different applied strains 0.4 ≤ e ≤ 11% were performed for two extrusion products exhibiting different microstructures. The main deformation mechanisms during cyclic loading are the formation of extension twins during compression and the detwinning during subsequent tensile loading. The strain-controlled fatigue tests were carried out with applied strain amplitudes 0.3 ≤ eA ≤ 5%. The tests were stopped at characteristic numbers of cycles N in the tensile or compression maximum of the hysteresis loop. The microstructural investigations deliver information about the type of twinning and the size, shape, local distribution, and volume fraction of twins as a function of the plastic deformation. These results will be discussed with regard to the microstructure of the initial state material and to the applied load.
Sotomi Ishihara - One of the best experts on this subject based on the ideXlab platform.
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The effect of load ratio on fatigue life and crack propagation behavior of an Extruded Magnesium alloy
International Journal of Fatigue, 2009Co-Authors: Sotomi Ishihara, Arthur J. Mcevily, Masanori Sato, K. Taniguchi, Tadashi GoshimaAbstract:Fatigue experiments were carried out in laboratory air using an Extruded Magnesium alloy, AZ31, to investigate the effect of load ratio on the fatigue life and crack propagation behavior. The crack propagation behavior was analyzed using a modified linear elastic fracture mechanics parameter, M. The relation crack propagation rate vs. M parameter was found to be useful in predicting fatigue lives at different R ratios. Good agreement between the estimated and the experimental results at each stress ratio was obtained.
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corrosion fatigue behavior of Extruded Magnesium alloy az31 in sodium chloride solution
International Journal of Fatigue, 2008Co-Authors: Sotomi Ishihara, T GoshimaAbstract:Abstract In the present study, corrosion fatigue experiments were done using the Extruded Magnesium alloy AZ31 in the 3% sodium chloride solution to clarify the corrosion fatigue characteristics of the material. Corrosion fatigue lives greatly decreased as compared with those in laboratory air. It was also clarified that most of the corrosion fatigue life (70–80%) at the lower stress amplitude is occupied with the period of the corrosion pit growth. Corrosion fatigue lives were evaluated quantitatively by dividing the corrosion fatigue process into the following two periods, i.e. (1) the corrosion pit growth period preceding the crack initiation from the pit and (2) the crack growth period before the specimen failure. In the analysis, the law of the corrosion pit growth proposed by authors was used to deal with the above first period. The evaluated results corresponded well to the experimental results.
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Fatigue Lives and Crack Propagation Behavior of the Extruded Magnesium Alloy Processed under Various Extrusion Conditions
Journal of Solid Mechanics and Materials Engineering, 2008Co-Authors: Sotomi Ishihara, Hiroshi Shibata, T Goshima, Arthur J. Mcevily, Masanori Sato, Masayoshi ShimizuAbstract:The fatigue properties of Extruded Magnesium alloy AZ31 were evaluated using material processed under two different extrusion ratios and two different extrusion temperatures. The effect of the extrusion ratios and extrusion temperatures on the fatigue lives and crack propagation behavior is discussed. The fatigue crack initiation and propagation processes were observed by the replica method. It was found that cracks initiated early in the fatigue process, and therefore the total fatigue life can be approximated as the crack propagation life. The crack propagation behavior observed in those materials was analyzed using a modified linear elastic fracture mechanics parameter, M. The relation crack propagation rate vs. M parameter was found to be useful in predicting fatigue lives and crack propagation curves.
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effect of extrusion ratio on fatigue properties of hot Extruded Magnesium alloys
Key Engineering Materials, 2007Co-Authors: Sotomi Ishihara, Hiroshi Shibata, Kenta Komano, Tadashi GoshimaAbstract:In the present study, fatigue experiments were conducted using two kinds of Extruded Magnesium alloys with different extrusion ratios. Effect of the extrusion ratio on fatigue lives and crack propagation behavior was studied in detail. There was no dramatic effect of the extrusion ratio on fatigue life, fatigue limit and crack propagation behavior.
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on the sharp bend of the s n curve and the crack propagation behavior of Extruded Magnesium alloy
Scripta Materialia, 2007Co-Authors: Z Y Nan, Sotomi Ishihara, Hiroshi Shibata, Arthur J. Mcevily, Kenta KomanoAbstract:Rotating bending fatigue tests were carried out using an Extruded Magnesium alloy in order to determine the shape of its S–N curve, and the crack initiation and propagation behavior. It was found that a well-defined knee in the S–N curve was related to the layered microstructure of the alloy, and that fatigue cracks initiated early stage in the fatigue life. The crack propagation behavior was analyzed using a modified linear elastic fracture mechanics parameter to predict crack growth behavior and the fatigue lifetimes.
Kenji Higashi - One of the best experts on this subject based on the ideXlab platform.
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Superplasticity in doubly Extruded Magnesium composite ZK60/SiC/17p
Materials Science and Technology, 1998Co-Authors: Toshiji Mukai, T. G. Nieh, H. Iwasaki, Kenji HigashiAbstract:AbstractSuperplasticity in a doubly Extruded Magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly Extruded and singly Extruded composites.
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superplasticity in doubly Extruded Magnesium composite zk60 sic 17p
Materials Science and Technology, 1998Co-Authors: Toshiji Mukai, T. G. Nieh, H. Iwasaki, Kenji HigashiAbstract:AbstractSuperplasticity in a doubly Extruded Magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly Extruded and singly Extruded composites.
Toshiji Mukai - One of the best experts on this subject based on the ideXlab platform.
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Microyielding and damping capacity in Magnesium
Scripta Materialia, 2014Co-Authors: Hiroyuki Watanabe, Tadaaki Sawada, Yasuyoshi Sasakura, Naoko Ikeo, Toshiji MukaiAbstract:The damping capacity and mechanical response under uniaxial tension and compression were examined for specimens of Extruded Magnesium inclined by 0°, 15° and 30° relative to the extrusion direction. It was found that both the microyielding under uniaxial deformation and the occurrence of strain-dependent damping capacity pertain to the same physical event: the breaking away of basal 〈a〉 dislocations from weak pinning points and the subsequent sweeping motion of dislocations between strong pinning points.
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Superplasticity in doubly Extruded Magnesium composite ZK60/SiC/17p
Materials Science and Technology, 1998Co-Authors: Toshiji Mukai, T. G. Nieh, H. Iwasaki, Kenji HigashiAbstract:AbstractSuperplasticity in a doubly Extruded Magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly Extruded and singly Extruded composites.
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superplasticity in doubly Extruded Magnesium composite zk60 sic 17p
Materials Science and Technology, 1998Co-Authors: Toshiji Mukai, T. G. Nieh, H. Iwasaki, Kenji HigashiAbstract:AbstractSuperplasticity in a doubly Extruded Magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly Extruded and singly Extruded composites.
