Synthesis and characterization of a ultrafine grained (CoCrFeNi)80Mn10Ti10 multi-principal element alloy nanocomposite

Abstract

In this paper, a ultrafine-grained (CoCrFeNi)80Mn10Ti10 multi-principal element alloy (MPEA) nanocomposite reinforced by TiO nanoparticles was fabricated by an innovation alliance of mechanical alloying (MA) and spark plasma sintering (SPS). The microstructural evolution, mechanical properties, strengthening mechanism, and fracture mechanism of the (CoCrFeNi)80Mn10Ti10 MPEA were investigated systematically. The (CoCrFeNi)80Mn10Ti10 MPEA powder presented BCC and FCC phases. Following SPS, the phase transformation from BCC to FCC phases has occurred in the (CoCrFeNi)80Mn10Ti10 MPEA. And the (CoCrFeNi)80Mn10Ti10 MPEA after SPS (referred as SPS11 MPEA) presented a bimodal microstructure consisted of ultrafine grained FCC matrix phase (∼285 nm) and uniformly dispersed TiO nanoparticles (∼87 nm). And a large number of annealing twins were also observed in the SPS11 MPEA. The SPS11 MPEA exhibited an excellent combination of compressive yield strength of 1500 MPa, compressive strength of 2700 MPa and strain of 36%. The nanoindentation tests showed that TiO phase possessed the higher nano-hardness, 12.92 GPa, while it was just 6.56 GPa for FCC matrix phase. According to the nanoindentation results, it is estimated that the TiO phase had the better anti-wear ability, compared to FCC phase in the SPS11 MPEA. The quantitative contributions of different strengthening mechanisms suggests the fine grain strengthening and dispersed oxide precipitation strengthening make the SPS11 MPEA possess excellent compressive yield strength and fracture strength. The high compression stain of the SPS11 MPEA is thought to be attributed to the formation of dislocations cell structure and deformation twins during plastic deformation.