Direct achievement of ultra-high strength and good ductility for high Co-Ni secondary hardening steel by combining spark plasma sintering and deformation.

• High Co-Ni steel was successfully synthesized by SPS and deformation process. • The ultra-high strength of 1997.3 MPa and good ductility of 11% was achieved. • The strengthening mechanism of the SPSed high Co-Ni steel was revealed. A combination of spark plasma sintering and deformation was developed to fabricate ultra-high strength steel with good ductility in this investigation. Microstructure and mechanical properties of the produced M54 steel were subsequently investigated. Martensite matrix produced by distinctive mechanism of spark plasma sintering led to ultra-high strength of the specimen S and D. Also, the specimen D exhibited good ductility due to gradually closing of micro-pores during SPS compression. Thus, based on the combined procedures, the produced high Co-Ni steel directly achieved ultra-high strength and good ductility without complicated traditional heat treatment process. [ABSTRACT FROM AUTHOR]