The microalloying effect of ce on the mechanical properties of medium entropy bulk metallic glass composites

Abstract

Novel ultra-strong medium entropy bulk metallic glasses composites (BMGCs) Fe65.4−x Cex Mn14.3 Si9.4 Cr10 C0.9 and Ti40−x Cex Ni40 Cu20 (x = 0, 1.0), through the martensite transformation induced plasticity (TRIP effect) to enhance both the ductility and work-hardening capability, were fabricated using magnetic levitation melting and copper mold suction via high frequency induction heating. Furthermore, the Ce microalloying effects on microstructure and mechanical behaviors were studied. The Fe-based BMGCs consisted of face-centered cubic (fcc) γ-Fe and body-centered cubic (bcc) α-Fe phase, as well as Ti-based BMGCs containing supercooled B2-Ti (Ni, Cu) and a thermally induced martensite phase B19’-Ti (Ni, Cu). As loading, the TRIP BMGCs exhibited work-hardening behavior, a high fracture strength, and large plasticity, which was attributed to the stress-induced transformation of ε-Fe martensite and B19’-Ti (Ni, Cu) martensite. Ce addition further improved the strengthening and toughening effects of TRIP BMGCs. Adding elemental Ce enhanced the mixing entropy ∆Smix and atomic size difference δ, while reducing the mixing enthalpy ∆Hmix, thus improving the glass forming ability and delaying the phase transition process, and hence prolonging the work-hardening period before fracturing. The fracture strength σf and plastic stress εp of Ti39 CeNi40 Cu20 and Fe64.4 CeMn14.3 Si9.4 Cr10 C0.9 alloys were up to 2635 MPa and 13.8%, and 2905 MPa and 30.1%, respectively.