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Min Song - One of the best experts on this subject based on the ideXlab platform.
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effects of temperature and alloying content on the phase transformation and 101 1 twinning in zr during rolling
Journal of Materials Science & Technology, 2020Co-Authors: Hao Zhang, X Z Liao, Min SongAbstract:Abstract The effects of temperature and Ti content on the deformation mechanisms of pure Zr and Zr-Ti alloys were investigated by transmission electron microscopy. The results indicate the existence of a relation between deformation-induced phase transformation from a Hexagonal Close-Packed Structure to a face-centered cubic Structure and { 10 1 ¯ 1 } deformation twinning. That is, when one is suppressed, the other will be promoted. The phase transformation was suppressed while the { 10 1 ¯ 1 } compressive twinning was promoted with increasing the rolling temperature and/or Ti content. This can be attributed to the activation of basal dislocations at high temperature and the increased stacking fault energy with Ti content.
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three dimensional crystallographic orientation relationships for Hexagonal close packed Structure to face centered cubic Structure transformation in pure titanium
Scripta Materialia, 2019Co-Authors: Bingqiang Wei, Yong Liu, Min SongAbstract:Abstract In this work, two types of stress induced Hexagonal close packed Structure to face centered cubic Structure transformation were observed in cold-rolled pure titanium. The corresponding transformation mechanisms were revealed by high resolution transmission electron microscopy. By using stereographic projections and selected area electron diffraction simulations, the three dimensional orientation relationships for the two types of phase transformation were deduced for the first time. The deduced orientation relationships were also verified by high resolution transmission electron microscopy observations, and the dark side of the basal-type face centered cubic phase was revealed at the atomic scale.
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proposed mechanism of twin formation during Hexagonal close packed Structure to face centered cubic phase transition
Solid State Communications, 2018Co-Authors: Jianshi Yang, L C Liu, H R Gong, Min SongAbstract:Abstract Detailed process, critical energy, and critical shear stress of twin formation during Hexagonal-Close-Packed (HCP) to face-centered-cubic (FCC) transition are proposed through first principles calculation. It reveals that a lower critical energy is needed for HCP→FCC basal transition with twin formation than that without twin. The relative magnitude of critical shear stresses is strongly correlated with c/a ratio of HCP metals, and fundamentally determines the appearance of HCP→FCC basal transition and phase-transition twin. The predicted results bring about reasonable explanations to two puzzling points regarding Mg and twin formation in the literature.
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mechanisms for deformation induced Hexagonal close packed Structure to face centered cubic Structure transformation in zirconium
Scripta Materialia, 2017Co-Authors: Henglv Zhao, Min SongAbstract:Abstract Two distinctive orientation relations between Hexagonal Close-Packed (HCP) phase and face-centered cubic (FCC) phase were observed simultaneously in cold-rolled pure Zr, which were denoted as B-type and P-type orientation relations according to whether the phase interface is parallel to the basal plane or prism plane of the HCP matrix. The mechanisms for the phase transformation generating the two different HCP-FCC orientation relations were thoroughly analyzed. B-type orientation relation was achieved when HCP to FCC phase transformation occurred via collective gliding of Shockley partial dislocations on basal planes, while P-type orientation relation was attained through pure-shuffle and shear-shuffle mechanisms.
Takayoshi Nakano - One of the best experts on this subject based on the ideXlab platform.
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development of ti zr hf y la high entropy alloys with dual Hexagonal close packed Structure
Scripta Materialia, 2020Co-Authors: Takeshi Nagase, Mitsuharu Todai, Takayoshi NakanoAbstract:Abstract TiZrHfYLa0.2 high-entropy alloys (HEAs) with dual Hexagonal-closed-packed (HCP) Structures were designed based on the concept of liquid phase separation (LPS) and segregation for enhancing the immiscibility of the constituent elements. The LPS leads to a particular solidification microStructure on the free surface side and Cu-hearth contacted area in the ingots. The dual HCP Structures with equi-axis Ti–Zr–Hf dendrite and Y-La-rich interdendrite were observed at most regions of the arc-melted ingots. The mixing enthalpy among the constituent elements and predicted phase diagrams constructed by the Materials Project were effective for the alloy design of the HEAs with dual HCP Structures.
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Plastic deformation mechanisms of biomedical Co–Cr–Mo alloy single crystals with Hexagonal Close-Packed Structure
Scripta Materialia, 2018Co-Authors: Wataru Kaita, Koji Hagihara, Luís Augusto Rocha, Takayoshi NakanoAbstract:Abstract This is the first report of the successful fabrication of Co–Cr–Mo biomedical alloy single crystals with a Hexagonal Close-Packed (hcp) Structure and the resultant clarification of its deformation behavior. The (0001)〈11 2 ¯ 0〉 basal and {1 1 ¯ 00}〈11 2 ¯ 0〉 prismatic slip systems were found to be predominately operative. The critical resolved shear stresses for the basal and prismatic slip systems at ambient temperature are ~ 204 and ~ 272 MPa, respectively, which are much higher than ~ 54 MPa for {111}〈11 2 ¯ 〉 slip in the face-centered cubic (fcc) Co–Cr–Mo phase, quantitatively demonstrating that the hcp phase acts as an effective strengthening phase.
Debin Shan - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Evolution and Mechanical Properties in Superlight Mg-Li Alloy Processed by High-Pressure Torsion
MDPI Open Access Publishing, 2019Co-Authors: Jae Ik Yoon, Debin Shan, Bin Guo, Hyoung Seop KimAbstract:Microstructural evolution and mechanical properties of LZ91 Mg-Li alloy processed by high-pressure torsion (HPT) at an ambient temperature were researched in this paper. The microStructure analysis demonstrated that significant grain refinement was achieved after HPT processing with an average grain size reducing from 30 mu m (the as-received condition) to approximately 230 nm through 10 turns. X-ray diffraction analysis revealed LZ91 alloy was consisted of ff phase (Hexagonal Close-Packed Structure, hcp) and beta phase (body-centered cubic Structure, bcc) before and after HPT processing. The mean value of microhardness increased with the increasing number of HPT turns. This significantly increased hardness of specimens can be explained by Hall-Petch strengthening. Simultaneously, the distribution of microhardness along the specimens was different from other materials after HPT processing due to the different mechanical properties of two different phases. The mechanical properties of LZ91 alloy processed by HPT were assessed by the micro-tensile testing at 298, 373, 423, and 473 K. The results demonstrate that the ultra-fine grain LZ91 Mg-Li alloy exhibits excellent mechanical properties: tensile elongation is approximately 400% at 473 K with an initial strain rate of 1 x 10(-2) s(-1).11
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microstructural evolution and mechanical properties in superlight mg li alloy processed by high pressure torsion
Materials, 2018Co-Authors: Qian Su, Jie Xu, Yuqiao Li, Jae Ik Yoon, Debin ShanAbstract:Microstructural evolution and mechanical properties of LZ91 Mg-Li alloy processed by high-pressure torsion (HPT) at an ambient temperature were researched in this paper. The microStructure analysis demonstrated that significant grain refinement was achieved after HPT processing with an average grain size reducing from 30 μm (the as-received condition) to approximately 230 nm through 10 turns. X-ray diffraction analysis revealed LZ91 alloy was consisted of α phase (Hexagonal Close-Packed Structure, hcp) and β phase (body-centered cubic Structure, bcc) before and after HPT processing. The mean value of microhardness increased with the increasing number of HPT turns. This significantly increased hardness of specimens can be explained by Hall-Petch strengthening. Simultaneously, the distribution of microhardness along the specimens was different from other materials after HPT processing due to the different mechanical properties of two different phases. The mechanical properties of LZ91 alloy processed by HPT were assessed by the micro-tensile testing at 298, 373, 423, and 473 K. The results demonstrate that the ultra-fine grain LZ91 Mg-Li alloy exhibits excellent mechanical properties: tensile elongation is approximately 400% at 473 K with an initial strain rate of 1 × 10−2 s−1.
R E Ryltsev - One of the best experts on this subject based on the ideXlab platform.
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a single phase sctizrhf high entropy alloy with thermally stable Hexagonal close packed Structure
Intermetallics, 2020Co-Authors: S A Uporov, Kh S Estemirova, V A Bykov, D A Zamyatin, R E RyltsevAbstract:Abstract High-entropy alloys forming non-cubic crystal Structures are intriguing systems for both scientific and functional viewpoints. Hexagonal-Structured HEAs are among them. In this work, we have fabricated a single-phase Hexagonal Close-Packed phase in ScTiZrHf system. To verify its structural stability, we anneal the alloy samples at 973 K for a long time from 15 up to 140 h. Structural analysis reveals that the HEA retains its single-phase Structure after the thermal treatment. To characterize the material, we examine its electron-transport and magnetic properties over a wide temperature range. The alloy electrical resistivity has purely metallic temperature dependence, while its absolute values are rather high. The thermal conductivity in this material is very low. The analysis of the transport properties reveals a noticeable lattice contribution ( ≈ 50% ) in total thermal conductivity probably caused by a strongly defected crystal Structure. The alloy magnetization demonstrates complicated temperature dependence, which is well described by a superposition of Curie–Weiss and valence-electron contributions. Based on this suggestion, we fit experimental magnetization data and extract the electron density of states (DOS) at the Fermi level as ≈ 1 e V − 1 . To address the properties of interatomic interaction in the system, we perform ab-initio molecular dynamics simulations of the liquid phase. The data obtained indicate unambiguously the absence of strong chemical interaction between alloy components as well as the nearly additive character of the liquid mixture that supports the results obtained experimentally.
M. C. Gao - One of the best experts on this subject based on the ideXlab platform.
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rare earth high entropy alloys with Hexagonal close packed Structure
Journal of Applied Physics, 2018Co-Authors: J W Qiao, Jeffrey A. Hawk, M L Bao, Y J Zhao, H J Yang, Yong Zhang, M. C. GaoAbstract:The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the Hexagonal Close-Packed (HCP) Structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. The corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs.The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the Hexagonal Close-Packed (HCP) Structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. The corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs.
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High-Entropy Alloys in Hexagonal Close-Packed Structure
Metallurgical and Materials Transactions A, 2016Co-Authors: M. C. Gao, S. M. Guo, B Zhang, J W Qiao, Jeffrey A. HawkAbstract:The microStructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic Structures have been studied extensively in the literature, but reports on HEAs in the Hexagonal Close-Packed (HCP) Structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.