@article{yang_chen_ma_zhong_zhao_xiao_fang_2021, title={Improvement of strength and ductility in a gradient structured Ni fabricated by severe torsion deformation}, volume={826}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2021.141980}, abstractNote={The tensile deformation behavior and microstructure evolution of gradient structured (GS) Ni processed by severe torsion deformation (STD) were systematically investigated. The results show that the gradient shear strain from STD introduces gradient distributions of grain size, microhardness, frequency of low angle grain boundaries, Σ3 twins and geometrically necessary dislocations (GND) density along the radial direction. With the increasing torsional angle of STD, the yield strength and ultimate tensile strength increase correspondingly while the uniform elongation first decreases and then increases. When the torsional angle increases to a maximum torsional revolution of 16, this specific GS Ni undergoes a maximum shear strain and lead to a promoted strength-ductility synergy, showing yield strength of 592 MPa, ultimate tensile strength of 1019 MPa and uniform elongation of 8.58%, as well as the highest work hardening rate. The simultaneous improvement of mechanical property is due to the strong partitioning between the fine grain region and central coarse grain region, which induces a significant work-hardening at the early plastic deformation stage. Therefore, a high shear strain and delicate control of its gradient in STD can lead to a unique gradient structure in metals, which is a good strategy to improve the mechanical properties of rod products.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Yang, Liang and Chen, Zhuo and Ma, Xinkai and Zhong, Dongling and Zhao, Xiaojun and Xiao, Lei and Fang, Xiaotian}, year={2021}, month={Oct} }
 @article{ma_li_sun_hou_fang_zhu_koch_2019, title={Achieving Gradient Martensite Structure and Enhanced Mechanical Properties in a Metastable beta Titanium Alloy}, volume={50A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-019-05157-5}, number={5}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Ma, Xinkai and Li, Fuguo and Sun, Zhankun and Hou, Junhua and Fang, Xiaotian and Zhu, Yuntian and Koch, Carl C.}, year={2019}, month={May}, pages={2126–2138} }
 @article{ma_li_fang_li_sun_hou_cao_2019, title={Effect of strain reversal on the stress-induced martensitic transformation and tensile properties of a metastable beta titanium alloy}, volume={784}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2019.01.010}, abstractNote={In this study, the effect of strain reversal on the evolution of microstructure and mechanical properties was investigated. Metastable β titanium alloy samples with single β phase were twisted up to 360° with different strain paths: monotonic torsion (MT) and cyclic forward-reverse torsion (CFRT). The results revealed CFRT with strain reversal accumulated lower dislocation density and less martensitic transformation in comparison with MT under the same accumulative strain. The stress-induced martensitic transformation (SIMT) was retarded by strain reversal and this suppression of martensitic transformation is more pronounced with the decreasing amplitude of strain reversal. It was further observed that CFRT samples with a gradient α″ martensite have a higher mechanical property both in strength and ductility than MT samples, which are due to interactions between α″ martensite and dislocation slip, especially the kinks of α″ martensite.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Ma, Xinkai and Li, Fuguo and Fang, Xiaotian and Li, Zhongkai and Sun, Zhankun and Hou, Junhua and Cao, Jun}, year={2019}, month={May}, pages={111–116} }
 @article{ma_li_sun_hou_li_fang_2019, title={Strain rate dependence of the indentation size effect in Ti-10V-2Fe-3Al alloy}, volume={35}, ISSN={["1743-2847"]}, DOI={10.1080/02670836.2019.1612596}, abstractNote={ The influence of strain rates on the indentation size effect (ISE) was explored experimentally. A strong ISE phenomenon on the hardness of Ti–10V–2Fe–3Al (Ti-1023) alloy was found when the peak-load was less than 3500 mN, regardless of the variation of loading rates. However, as indenter strain rates increased, the degree of ISE reduced considerably, which was related to the decrease of the internal indentation length scale ranging from 23.08 to 6.80 µm. Furthermore, a positive strain rate sensitivity of the hardness in the whole peak-load range was found in Ti-1023 alloy, which showed a linear function of indenter load. The underlying mechanism was well explained by the variation of geometrically necessary dislocation and statistically stored dislocations in Ti-1023 alloy. }, number={9}, journal={MATERIALS SCIENCE AND TECHNOLOGY}, author={Ma, Xinkai and Li, Fuguo and Sun, Zhankun and Hou, Junhua and Li, Jinghui and Fang, Xiaotian}, year={2019}, month={Jun}, pages={1107–1113} }