Influence of Co addition on the deformation behavior and mechanical properties of Ni–16Cr–11Mo–2Cu alloy

Abstract The roles of Co on the strain-hardening behavior, deformation mechanism, mechanical properties and facture mode of Ni–16Cr–11Mo–2Cu alloy were thoroughly investigated using tensile tests, SEM, EBSD, TEM and HRTEM. Two alloys with a similar sole FCC-γ phase constitution, near grain size only except the composition difference of 30 wt% Co were fabricated in purpose. Co addition can overcome the strength-ductility trade-off by enhancing the strain-hardening rate and capacity. The deformation behavior evolves from slip-dominated to SFs-dominated after Co addition, due to significant decrease of stacking fault energy, the critical stresses for both SFs and twinning by Co addition. In terms of facture mode, dimples-dominated ductile fracture is transformed to quasi-cleavage fracture composed of cleavage planes and dimples after Co addition. This is probably owing to the special role of SFs on intensifying stress/strain incompatibility phenomenon in polycrystalline alloys.