Microstructure and mechanical properties of lightweight Ti3Zr1.5NbVAlx(x=0,0.25,0.5 and 0.75) refractory complex concentrated alloys

Combining high strength and good ductility is an urgent requirement for traditional structural materials,but yet a challenge.Newly emerging ductile Ti3Zr1.5VNbAlx(x=0,0.25,0.5,0.75) refractory complex concentrated alloys(RCCAs) with high specific strength were designed and synthesized via vacuum arc-melting.Alloying effects of Al on microstructure and mechanical properties were systematically investigated.It was found that the phase composition in this alloy system changes from the single disordered body-centered cubic(BCC) phase to a nano-scale mixture of co-continuous disordered BCC and ordered B2 phases with the increase of Al concentration.This structure transition results in a remarkable increase in the yield strength of the RCCAs,i.e.,from 790 to 1118 MPa,leading to a superior specific yield strength of 199.4 MPa cm3g-1for the Al0.75 alloy,meanwhile,the tension plasticity maintained at～10%.TEM observation demonstrates that cell-forming structure and HDDWs induced by wave slip play a crucial role of considerable plasticity in Al0.25 alloy,whereas in Al0.5 alloy,microbands induced by planar slip dominant deformation behavior.The current work is important not only for providing novel high strength and tough structural materials with low density,but also sheds light on designing highperformance lightweight alloys with tunable microstructure.