Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical p...Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.展开更多
A large-sized CuZr-based bulk metallic glass （BMG） composite with enhanced mechanical properties is prepared successfully. With the addition of Ta to CuZr-based alloys, the critical composite size changes and the mi...A large-sized CuZr-based bulk metallic glass （BMG） composite with enhanced mechanical properties is prepared successfully. With the addition of Ta to CuZr-based alloys, the critical composite size changes and the microstructure diversifies. The composite with 0.5 at,% Ta addition has the largest critical size with the microstructure of single CuZr（B2） phase uniformly dispersing in amorphous matrix. This composite exhibits good mechanicat properties, i.e., large compressive plasticity and work-hardening ability, which should be attributed to the uniformly distributed CuZr（B2） phase. The increased critical size of CuZr-based BMG composite can be explained by the fact that proper Ta addition can suppress the precipitation of crystalline phases other than B2 CuZr phase during solidification. This study may be helpful for the fabrication of large- sized BMG composites with excellent mechanical properties.展开更多
Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr mart...Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents（i.e.,7.0,10.0,and 14.0at.%）,the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature（M_s）decreases from（412±5）K to（329±5）K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons（i.e.,e_v/a and c_v）,respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.展开更多
基金L.Deng acknowledges financial support by the Chinese Scholarship Council(CSC)support by German Research Foundation(DFG)(Nos.PA 2275/4-1,PA2275/6-1 and KO5771/1-1)+1 种基金support by the National Natural Science Foundation of China(Nos.51701213 and 51790484)the National key research and development program(2018YFB0703402)。
文摘Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.
基金financially supported by the National Natural Science Foundation of China (NSFC, Granted Nos. 51161130526 and 51101004)
文摘A large-sized CuZr-based bulk metallic glass （BMG） composite with enhanced mechanical properties is prepared successfully. With the addition of Ta to CuZr-based alloys, the critical composite size changes and the microstructure diversifies. The composite with 0.5 at,% Ta addition has the largest critical size with the microstructure of single CuZr（B2） phase uniformly dispersing in amorphous matrix. This composite exhibits good mechanicat properties, i.e., large compressive plasticity and work-hardening ability, which should be attributed to the uniformly distributed CuZr（B2） phase. The increased critical size of CuZr-based BMG composite can be explained by the fact that proper Ta addition can suppress the precipitation of crystalline phases other than B2 CuZr phase during solidification. This study may be helpful for the fabrication of large- sized BMG composites with excellent mechanical properties.
基金Item Sponsored by National Natural Science Foundation of China(51501103)Fundamental Research Funds for the Central Universities on Northwestern Polytechnical University of China(GEKY1008)
文摘Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents（i.e.,7.0,10.0,and 14.0at.%）,the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature（M_s）decreases from（412±5）K to（329±5）K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons（i.e.,e_v/a and c_v）,respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.
