Shun Guo

Origin of ultralow Young׳s modulus in a metastable β-type Ti-33Nb-4Sn alloy.

Although there is difficulty in growing a Ti-33Nb-4Sn single crystal due to its ultralow β-phase stability, the single-crystal elastic constants of metastable β-type Ti-33Nb-4Sn (wt%) alloy were extracted successfully from its polycrystal by in-situ synchrotron X-ray diffraction technique, to clarify the origin of the ultralow Youngs modulus in its polycrystal. It is indicated that compared to binary TiCr, TiV and TiNb alloys, the Ti-33Nb-4Sn alloy possesses slightly lower β-phase stability with respect to {110}<110>(-)shear (i.e., C׳) but much lower β-phase stability regarding to {001}〈100〉 shear (i.e., C44). An analysis by the Hill approximation suggests that the ultralow isotropic polycrystalline Young׳s modulus (EH) of Ti-33Nb-4Sn alloy originates from the extremely low shear modulus C44 as well as the relatively low C׳. This indicates that in addition to C׳, C44 has a significant contribution to the Youngs modulus of polycrystal, which challenges a conventional understanding that the Youngs modulus of β-type Ti alloys is predominantly determined by C׳.

Wear response of metastable β-type Ti–25Nb–2Mo–4Sn alloy for biomedical applications

The wear response of a newly developed metastable β-type Ti–25Nb–2Mo–4Sn (abbreviated as Ti-2524) alloy was investigated and compared with that of (α+β)-type Ti–6Al–4V alloy. Experimental results show that solution-treated (ST) Ti-2524 specimen has the lowest wear rate due to the combined effects of excellent ductility and lubricative Nb2O5. Although similar Nb2O5 forms on the surface of the cold rolled plus annealed (CRA) Ti-2524 specimen, the beneficial effect of Nb2O5 on the wear resistance is counteracted by the increase in wear rate caused by low elongation. Thus, the wear rate of the CRA Ti-2524 alloy is higher than that of ST Ti-2524 specimen. As for the ST Ti–6Al–4V alloy, no lubricative Nb2O5 forms on its worn surface owing to the absence of Nb. In addition, the ST Ti–6Al–4V alloy exhibits an elongation roughly similar to the CRA Ti-2524 specimen. Therefore, the ST Ti–6Al–4V specimen possesses a higher wear rate than the CRA Ti-2524 specimen.

Direct evidence for competition between metastable ω and equilibrium α phases in aged β-type Ti alloys

Precipitation response of a recently developed β-type Ti–25Nb–2Mo–4Sn alloy (wt%) during aging was investigated in detail. Experimental results indicate that the metastable ω or equilibrium α phase can form alternatively even under the same aging condition, depending on the condition prior to the aging, i.e., solution treatment or severe cold rolling. This provides, for the first time, the direct evidence for the competition between ω and α in aged β-type Ti alloys. This peculiar aging response is found to be closely related to high-density dislocations and grain boundaries which suppress the formation of ω but favor the precipitation of fine α phase.

Rare earth texture analysis of rectangular extruded Mg alloys and a comparison of different alloying adding ways

The microstructures and textures of four rectangular extruded Mg alloys, Mg–3Gd, Mg–3Nd, Mg–1Gd–1Nd and Mg–1.5Gd–1.5Nd (all in wt%) were investigated by using optical microscopy (OM), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The results demonstrate that the extruded alloys all reveal fully recrystallized microstructure and weak non-basal texture. For textures of the four extruded alloys, it is shown that the basal planes of majority grains tilt away from the sheet plane normal toward the extrusion direction. Compared with two binary alloys, the ternary alloys possess weaker texture strengths. Through orientation distribution function analysis, two types of rare earth textures, {01

A β-type TiNbZr alloy with low modulus and high strength for biomedical applications

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Tribological properties of Cu-based composites with S-doped NbSe2

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Effect of thermo-mechanical treatment on mechanical and elastic properties of Ti–36Nb–5Zr alloy

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