@article{xiao_chen_wei_liu_yin_hu_zhou_zhu_2021, title={Effect of dislocation configuration on Ag segregation in subgrain boundary of a Mg-Ag alloy}, volume={191}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2020.08.040}, abstractNote={Interfacial segregation has been reported to play a critical role in the thermal-mechanical stability of nanocrystalline Mg alloys. Here we report Ag-segregation-assisted formation of nanocrystalline Mg-Ag alloy with high proportion of sub-grain boundaries during conventional rolling. The segregation structure is determined by dislocation configurations and subsequent strain field and misorientation of the sub-grain boundary. It indicates that the alloying elements, which induce <c+a> dislocations, would help to improve the stability of interfaces.}, journal={SCRIPTA MATERIALIA}, author={Xiao, Lirong and Chen, Xuefei and Wei, Kang and Liu, Yi and Yin, Dongdi and Hu, Zhaohua and Zhou, Hao and Zhu, Yuntian}, year={2021}, month={Jan}, pages={219–224} }
 @article{liu_cao_mao_zhou_zhao_jiang_liu_wang_you_zhu_2020, title={Critical microstructures and defects in heterostructured materials and their effects on mechanical properties}, volume={189}, ISSN={["1873-2453"]}, url={https://doi.org/10.1016/j.actamat.2020.03.001}, DOI={10.1016/j.actamat.2020.03.001}, abstractNote={Systematic study was conducted on the microstructures and mechanical properties of nickel samples with two distinct types of heterostructures. The first is featured with coarse-grained lamellae embedded in a matrix consisting of a very high density of dislocation structures. The second is featured with coarse-grained zones embedded in the ultrafine-grained matrix. The second type of heterostructures exhibits better strength and ductility, although it has a smaller average grain size than the first type. The zone boundaries in the second type of heterostructures are less prone to cracking than those in the first type. Intersecting micro-shear-bands formed net-like patterns in the second type of heterostructures during tensile deformation. This is the first ever observation of structural micro-shear-bands in a heterostructured material. It supports the claim that heterostructure promotes the formation of dispersive shear bands. In contrast, a macroscopic shear band formed and caused early failure of the sample with the first type of heterostructures. Our results indicate that well-developed ultrafine/nano grained matrix in heterostructured materials are necessary for preventing crack formation and shear band localization. This should be considered as a key factor for optimizing the mechanical properties of heterostructured materials.}, journal={ACTA MATERIALIA}, author={Liu, Yanfang and Cao, Yang and Mao, Qingzhong and Zhou, Hao and Zhao, Yonghao and Jiang, Wei and Liu, Ying and Wang, Jing Tao and You, Zesheng and Zhu, Yuntian}, year={2020}, month={May}, pages={129–144} }
 @article{liu_cao_zhou_chen_liu_xiao_huan_zhao_zhu_2020, title={Mechanical Properties and Microstructures of Commercial-Purity Aluminum Processed by Rotational Accelerated Shot Peening Plus Cold Rolling}, volume={22}, ISSN={["1527-2648"]}, DOI={10.1002/adem.201900478}, abstractNote={Commercial‐purity aluminum with 99.7% purity is processed by rotational accelerated shot peening (RASP) and cold‐rolling. RASP samples are rolled at room temperature to a thickness reduction of 20% and 30%, for the purpose of surface roughness reduction and strengthening. Detailed microstructural characterization and hardness tests reveal that cold‐rolling cause grain growth at the surfaces of RASP samples from ≈472 to ≈1000 nm. Moderate cold‐rolling is effective in smoothing the surface of RASP samples, while improving strength and maintaining ductility. However, cold‐rolling to more than 30% thickness reduction eventually diminishes the gradient nanostructure. During cold‐rolling of RASP samples, a transition zone with strong strain incompatibility is noticed by a sharp rise in hardness at some point of the hardness‐distribution curve from the surface to the core of the sample. This transition zone is a result of quick generation of geometrically necessary dislocations. Although the transition zone with strong strain incompatibility is short‐lived, it is anticipated to be common among gradient‐nanostructured materials under cold‐rolling condition.}, number={1}, journal={ADVANCED ENGINEERING MATERIALS}, author={Liu, Yanfang and Cao, Yang and Zhou, Hao and Chen, Xuefei and Liu, Ying and Xiao, Lirong and Huan, Xiaowei and Zhao, Yonghao and Zhu, Yuntian}, year={2020}, month={Jan} }
 @article{jiang_zhou_cao_nie_li_zhao_kawasaki_langdon_zhu_2020, title={On the Heterogeneity of Local Shear Strain Induced by High-Pressure Torsion}, volume={22}, ISSN={["1527-2648"]}, DOI={10.1002/adem.201900477}, abstractNote={A ductile duplex stainless steel consisting of a ferrite phase and an austenitic phase is chosen as a model material to investigate the development of shear strain patterns under high‐pressure torsion. Systematic analysis on the macroscopic and microscopic heterogeneities of local shear strain reveals that complex shear patterns can be developed only above a high strain level where the grain sizes are already refined to a steady state. It is concluded that grain boundary‐mediated deformation mechanisms provide sufficient freedom for reshaping the austenite phase domains, and thus the intrinsic factor required for the formation of these complicated shear patterns is well‐developed ultrafine grains and/or nanograins.}, number={1}, journal={ADVANCED ENGINEERING MATERIALS}, author={Jiang, Wei and Zhou, Hao and Cao, Yang and Nie, Jinfeng and Li, Yusheng and Zhao, Yonghao and Kawasaki, Megumi and Langdon, Terence G. and Zhu, Yuntian}, year={2020}, month={Jan} }
 @article{sha_xiao_chen_cheng_yu_yin_zhou_2019, title={Atomic structure of gamma '' phase in Mg-Gd-Y-Ag alloy induced by Ag addition}, volume={99}, ISSN={["1478-6443"]}, DOI={10.1080/14786435.2019.1606466}, abstractNote={ABSTRACT Mg–Gd based alloys are typical high strength magnesium alloys owing to their outstanding age hardening behavior. The mechanical strength of aged Mg–Gd alloys is enhanced by high density prismatic-shaped precipitates in Mg matrix. Moreover, the addition of Ag has been found to enhance the strength of Mg–Gd based alloys further by forming a plate-shaped precipitate, named as γ″, on basal planes of Mg. However, the structure of this precipitate is not well understood due to the complex alloying system. In this work, the atomic structure of γ″ phase is investigated using atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Based on the accurate atomic structure from three independent directions, e.g. in [0001]Mg, [110]Mg and [010]Mg zone axes, the unit cell of γ″ is well established. The γ″ phase has a hexagonal structure, and its lattice parameters are a = 0.55 nm and c = 0.42 nm. The orientation relationship between γ″ phase and Mg matrix is (0001)γ″//(0001)Mg and <110>γ″//<010>Mg.}, number={16}, journal={PHILOSOPHICAL MAGAZINE}, author={Sha, Xuechao and Xiao, Lirong and Chen, Xuefei and Cheng, Guangming and Yu, Yandong and Yin, Dongdi and Zhou, Hao}, year={2019}, month={Aug}, pages={1957–1969} }
 @article{zhou_huang_sha_xiao_ma_hoeppel_goeken_wu_ameyama_han_et al._2019, title={In-situ observation of dislocation dynamics near heterostructured interfaces}, volume={7}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2019.1616330}, abstractNote={ABSTRACT There has been a long-standing controversy on how dislocations interact with interfaces. Here we report in-situ observations that in a Cu–brass heterostructured TEM film Frank–Read sources are the primary dislocation sources. They were dynamically formed and deactivated throughout the deformation in grain interior, which has never been reported before. This observation indicates that strain gradient near interfaces cannot be quantitatively related to the density gradient of geometrically necessary dislocations, and it was primarily produced by Frank–Read source gradient instead of dislocation pile-ups. These findings provide new insights on how to design heterostructured interfaces to enhance mechanical properties. GRAPHICAL ABSTRACT}, number={9}, journal={MATERIALS RESEARCH LETTERS}, author={Zhou, Hao and Huang, Chongxiang and Sha, Xuechao and Xiao, Lirong and Ma, Xiaolong and Hoeppel, Heinz Werner and Goeken, Mathias and Wu, Xiaolei and Ameyama, Kei and Han, Xiaodong and et al.}, year={2019}, pages={376–382} }
 @article{liu_wang_cao_nie_zhou_yang_liu_an_liao_zhao_et al._2019, title={Unique defect evolution during the plastic deformation of a metal matrix composite}, volume={162}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2018.11.038}, abstractNote={During the plastic deformation of a metal matrix composite (MMC) containing non-deformable particles, high dislocation density and strong back stresses are expected because the particles help with blocking and accumulating dislocations. Here we report that the MMC has lower, instead of higher, dislocation density than the corresponding monolithic matrix material when they are deformed to high plastic strains, because smaller sub-grains in the MMC lowered dislocation generation rate and meanwhile promoted the dislocation interaction and annihilation in the matrix. This unique defect density evolution is a hitherto unknown but important factor affecting the mechanical properties of MMCs.}, journal={SCRIPTA MATERIALIA}, author={Liu, Yanfang and Wang, Fang and Cao, Yang and Nie, Jinfeng and Zhou, Hao and Yang, Huabing and Liu, Xiangfa and An, Xianghai and Liao, Xiaozhou and Zhao, Yonghao and et al.}, year={2019}, month={Mar}, pages={316–320} }
 @article{cai_ma_moering_zhou_yang_zhu_2015, title={Enhanced mechanical properties in Cu-Zn alloys with a gradient structure by surface mechanical attrition treatment at cryogenic temperature}, volume={626}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2014.12.070}, abstractNote={This paper describes the effects of gradient structure on mechanical properties of Cu–Zn alloys processed by surface mechanical attrition treatment (SMAT) at liquid nitrogen temperature (77 K). This method leads to the formation of a gradient structure with surface fine-grained regions and a coarse-grained interior. In this study, a fine-grained surface layer with a thickness of 10 μm is formed on a coarse-grained Cu–Zn alloy sheet after the cryogenic SMAT process. Microstructural observations and microhardness measurements demonstrate that a significant microstructure refinement in grain size and a gradient increase in hardness from the coarse-grained core to the top surface. Tensile tests at room temperature showed superior strength–ductility synergy for the SMAT sample.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Cai, Baozhuang and Ma, Xiaolong and Moering, Jordan and Zhou, Hao and Yang, Xincheng and Zhu, Xinkun}, year={2015}, month={Feb}, pages={144–149} }
 @article{zhou_wang_guo_ye_jian_xu_ma_moering_2015, title={Finite element simulation and experimental investigation on homogeneity of Mg-9.8Gd-2.7Y-0.4Zr magnesium alloy processed by repeated-upsetting}, volume={225}, ISSN={["0924-0136"]}, DOI={10.1016/j.jmatprotec.2015.06.010}, abstractNote={A novel severe plastic deformation (SPD) process called repeated-upsetting (RU), which produces homogenous samples of large size, is employed to process a high performance magnesium alloy Mg-9.8Gd-2.7Y-0.4Zr at 350 °C with 1–4 passes. Homogenous microstructure and mechanical properties can be achieved after 4 passes of RU. Experimental and finite-element modeling results show that effective strain accumulation with more passes can improve both grain refinement and micro-hardness of samples.}, journal={JOURNAL OF MATERIALS PROCESSING TECHNOLOGY}, author={Zhou, H. and Wang, Q. D. and Guo, W. and Ye, B. and Jian, W. W. and Xu, W. Z. and Ma, X. L. and Moering, J.}, year={2015}, month={Nov}, pages={310–317} }
 @article{yang_ma_moering_zhou_wang_gong_tao_zhu_zhu_2015, title={Influence of gradient structure volume fraction on the mechanical properties of pure copper}, volume={645}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2015.08.037}, abstractNote={This paper reports the influence of gradient structure volume fraction on the tensile mechanical behaviors of pure copper processed by surface mechanical attrition treatment at cryogenic temperature. Superior combinations of tensile strength and ductility are observed in a certain volume fraction, in which strain hardening uprising after yielding is also observed. The gradient structure produces a synergetic strengthening and extra work hardening. These findings suggest the existence of an optimum volume fraction of gradient structure for the best mechanical properties.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Yang, Xincheng and Ma, Xiaolong and Moering, Jordan and Zhou, Hao and Wang, Wei and Gong, Yulan and Tao, Jingmei and Zhu, Yuntian and Zhu, Xinkun}, year={2015}, month={Oct}, pages={280–285} }
 @article{ma_zhou_narayan_zhu_2015, title={Stacking-fault energy effect on zero-strain deformation twinning in nanocrystalline Cu-Zn alloys}, volume={109}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2015.07.027}, abstractNote={It has been reported that most deformation twins in nanocrystalline face-centered-cubic metals do not produce macroscopic strain. Here we report the decrease of zero-strain deformation twinning with decreasing stacking-fault energy. One of the two major mechanisms that produce zero-strain twinning is cooperative slip of three partials under external applied stress. Lower stacking-fault energy weakens this mechanism and statistically reduces the fraction of twins with zero-strain.}, journal={SCRIPTA MATERIALIA}, author={Ma, X. L. and Zhou, H. and Narayan, J. and Zhu, Y. T.}, year={2015}, month={Dec}, pages={89–93} }