Microstructure and mechanical properties of NiCoCrMoW medium-entropy alloys via controlling of cobalt content and Al/Ti co-doping

The microstructure and mechanical properties of NiCoCrMoW alloys with different Co and Al/Ti co-doping contents were investigated. The strength and hardness of the alloys were enhanced with the increase of Co content, and alloys with different Co contents all form an FCC phase. However, with the increase in Al/Ti co-doping content, the grain size of the alloy decreased, and the phase composition of the alloys changed from FCC and B2 phases to FCC, B2, and μ phases. The tensile strength , yield strength, and hardness of alloys increased. Among them, Ni 34.5 Co 42.5 Cr 5 Mo 5 W 5 Al 6 Ti 2 exhibited the best mechanical properties, with a tensile strength of up to 1287 MPa and an elongation of up to 35 %. Aging treatment promoted the precipitation of the L1 2 phase, resulting in a significant increase in the yield strength. These results provide guidance for the composition and processing design of NiCoCrMoW alloys. • The more Co and Al/Ti co-doping content, the greater the strength and hardness. • With the increase of Al/Ti co-doping content, the phase changed from FCC and B2 to FCC, B2 and μ phases. • After aging, the yield strength can be significantly increased.