Exceptional strength-ductility synergy of additively manufactured CoCrNi medium-entropy alloy achieved by lattice defects in heterogeneous microstructures. (10th November 2022)

• Record Type: Journal Article
• Authors: Wang, Jianying; Zou, Jianpeng; Yang, Hailin; Zhang, Lijun; Liu, Zhilin; Dong, Xixi; Ji, Shouxun
• Is Part Of: Journal of materials science & technology. Volume 127(2022)
• Page Start: 61
• Page End: 70
• Publication Date: 2022-11-10
• Subjects: Medium-entropy alloys -- Selective laser melting -- Strength-ductility synergy -- Defects -- Microstructure; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2022.03.024
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Giant strengthening in SLMed CoCrNi alloys by subsequent deformation and annealing. CoCrNi alloy delivers yield strength of 1161.6 MPa and strain of 31.5%. The refined hierarchical microstructure and lattice defects result in high strength. Abstract: The selective laser melting (SLM) with subsequent cold rolling and annealing is used to produce high-density lattice defects and grain refinement in the CoCrNi medium-entropy alloys (MEAs). The superior comprehensive mechanical properties have been achieved in the as-SLMed CoCrNi alloy after rolling and annealing. The as-SLMed alloys delivered the yield strength of 693.4 MPa, the ultimate tensile strength of 912.7 MPa and the fracture strain of 54.4%. After rolling with 70% reduction in thickness and annealing at 700 °C for 2 h. the yield strength, ultimate tensile strength and fracture strain reached 1161.6 MPa, 1390.8 MPa and 31.5%, respectively. The exceptional strength-ductility synergy is mainly attributed to the refined hierarchical microstructures with coarsening grains at a level of 30 µm and ultrafine grains at a level of 1 µm, and the heritage of dislocation-formed sub-grains and other lattice defects. This investigation demonstrates that the SLM with subsequent rolling and annealing is beneficial to fabricate high strength and ductile MEAs with single face-centered cubic (fcc) structure.