| 1 | Enhanced dynamic deformability and strengthening effect via twinning and microbanding in high density NiCoFeCrMoW high-entropy alloys显示文摘High density alloys with enhanced deformability and strength are urgently required in energy,military and nuclear industries,etc.In this work,we present a new kind of NiCoFeCrMoW high entropy alloys(HEAs)which possess higher densities and sound velocities than copper.We systematically investigate the phase structure,quasi-static tensile,dynamic compression and related deformation mechanism of these HEAs.It is shown that single FCC or FCC+μdual phases were formed in the HEAs depending on Mo and W content and annealing temperature.Excellent quasi-static tensile and dynamic compression properties have been achieved for these HEAs,e.g.Ni_(30)Co_(30)Fe_(21)Cr_(10)W_(9)HEA annealed at 1573 K exhibited a yield and ultimate tensile strength and elongation of~364 MPa,~866 MPa and~32%,respectively,in quasi-static test;a yield strength of~710 MPa and no fracture under the dynamic strain rate of 4100 s^(-1).Superior strain rate sensitivity(SRS)of yield strength than that of previously reported FCC HEAs have been evidenced.The dynamic stress-strain constitutive relation can be described by the modified Johnson-Cook model.As for the dynamic deformation mechanism,it is envisaged that the regulation of stacking fault energy and Peierls barrier in current HEAs resulted in occurrences of abundant nanoscale deformation twins and microbands during high strain rate compression.The synergistic microbanding and twinning effectively contributes to the enhanced dynamic deformability and strengthening effect.Besides,the interactions of dislocations with precipitates,stacking faults(SFs)with twins,and between SFs also contribute to extraordinary work-hardening capacity. | Xuli Liu Yidong Wu Yansong Wang Jinbin Chen Rui Bai Lei Gao Zhe Xu William Yi Wang Chengwen Tan Xidong Hui | 2022 | Journal of Materials Science & Technology2022，，32： | 1 |
| 4 | Differential bone metabolism and protein expression in mice fed a high-fat diet versus Daurian ground squirrels following natural pre-hibernation fattening显示文摘This study compared the effects on bone metabolism and morphology of pathological obesity induced by excessive fat intake in a non-hibernator(mice)versus healthy obesity due to pre-hibernation fattening in a hibernator(ground squirrels).Kunming mice were fed a high-fat diet to provide a model of pathological obesity(OB group).Daurian ground squirrels fattened naturally in their pre-hibernation season(PRE group)were used as a healthy obesity model.Micro-computed tomography(micro-CT)and three-point bending tests were used to determine the microstructure and mechanical properties of bone.Western blots were used to analyze protein expression levels related to bone metabolism(Runt-related transcription factor 2(RunX2),osteocalcin(OCN),alkaline phosphatase(ALP),osteoprotegerin(OPG),receptor activator of nuclear factor-κB ligand(RANKL),cathepsin K,matrix metallopeptidase 9(MMP9),patched protein homolog 1(Ptch1),phosphorylatedβ-catenin(P-β-catenin),and glycogen synthase kinase-3β(GSK-3β)).Compared with controls,there was no obvious bone loss in the OB mice,and the stiffness of the femur was increased significantly.Compared with summer active squirrels,bone formation was enhanced but the mechanical properties did not change in the PRE group squirrels.In OB mice,western blots showed significantly increased expression levels of all proteins except RunX2,OPG,and Ptch1.PRE ground squirrels showed significantly increased expression of most proteins except OCN and Ptch1,which decreased significantly,and P-β-catenin and OPG,which did not change.In conclusion,for non-hibernating mice,moderate obesity had a certain protective effect on bones,demonstrating two-way regulation,increasing both bone loss and bone formation.For pre-hibernating ground squirrels,the healthy obesity acquired before hibernation had a positive effect on the microstructure of bones,and also enhanced the expression levels of proteins related to bone formation,bone resorption,and Wnt signaling. | Xuli GAO Shenyang SHEN Qiaohua NIU Weilan MIAO Yuting HAN Ziwei HAO Ning AN Yingyu YANG Yu ZHANG Han ZHANG Kenneth BSTOREY Hui CHANG | 2022 | Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)2022，23，12： | 0 |
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