Simultaneously improved the strength and ductility of laser powder bed fused Al-Cr-Fe-Ni-V high-entropy alloy by hot isostatic pressing:Microcrack closure and precipitation strengthening  

作　　者：Ziwei Liu Zhen Tan Dingyong He Zheng Zhou Xingye Guo Wei Shao Haihua Yao Yunfei Xue Li Cui 

机构地区：[1]Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124,China [2]Beijing Engineering Research Center of Eco-materials and LCA,Beijing 100124,China [3]School of Materials Science and Engineering,Beijing Institute of Technology,Beijing 100081,China

出　　处：《Journal of Materials Science & Technology》2024年第13期55-68,共14页材料科学技术（英文版）

基　　金：National Natural Science Foundation of China(Grant Nos.51901004,52001025,and 52171060);State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.

摘　　要：Hot isostatic pressing(HIP)is usually applied to reduce the defects including cracks and pores in the materials prepared by laser powder bed fusion(LPBF).In the present research,in order to improve the relative density and mechanical property,HIP was employed on the LPBF-processed Al-Cr-Fe-Ni-V high-entropy alloy(HEA)with microcracks and pores.The microstructure evolution and property improvement induced by HIP were investigated.In the LPBF-processed HEA,the microcracks were caused by residual stress and element segregation,and these microcracks as well as the pores reduced significantly after HIP treatments.Remarkably,HIP temperature has a more critical effect on the microcrack closure than the holding time,thus,microcracks and pores still existed after HIP-1 treatment(1273 K,8 h),while HIP-2 treatment(1473 K,4 h)could close the microcracks significantly.The crack closure was attributed to the interfacial diffusion of the alloying element under high temperature accompanied by high pressure,and the degree of element diffusion at both interfaces of the cracks determined the bonding strength after crack closure.Higher temperatures at high pressure induced more adequate element diffusion and higher bonding strength.The above high temperature and high pressure also induced the growth of the L1_(2) phase and the precipitation of the B2 phase in HEA.Consequently,the tensile strength and elonga-tion of the LPBF-processed HEA after HIP-2 treatment were simultaneously enhanced(80.7%and 222.5%higher than that of LPBF-processed HEA,respectively).This could be attributed to the combined effect of microcrack/pore closure and precipitation strengthening.The strengthening effect of the B2 phase and L1_(2) phase accounted for 53%(dislocation by-pass mechanism)and 47%(dislocation shearing mechanism)of the total precipitation strengthening,respectively.

关 键 词：High-entropy alloy Laser powder bed fusion Hot isostatic pressing Crack closure Precipitation strengthening 

分 类 号：TG146.23[一般工业技术—材料科学与工程]