Microstructure and mechanical properties of Ti_x(AlCrVNb)_100-x light weight multi-principal element alloys

The Ti_x(AlCrVNb)_100-x (x = 20, 40, 60 and 80) low-density multi-principal element alloys (MPEAs) were prepared by vacuum arc-melting. The density, crystal structure, microstructure and mechanical properties of this new Ti_x(AlCrVNb)_100-x are reported. The density of alloys decreases with increasing Ti content from 5.81 to 4.79 g/cm³. The microstructure of Ti20 consists of body-centered cubic (BCC) and minor amount of nano-sized particles segregating at grain boundaries, resulting in the brittleness of Ti20. But Ti40, Ti60 and Ti80 all consist of a single BCC solid solution phase. In addition, the experimentally observed phase constitutions are compared with the equilibrium and non-equilibrium thermodynamical modeling results. The compression yield strength decreases from 1122 MPa for Ti40 to 600 MPa for Ti80, due to the decreased atomic size difference. The combination of room-temperatured specific strength and ductility of Ti40 was found to be superior to most single-phase BCC MPEAs in the as-cast state. Promising room-temperature tensile properties were found for Ti60, better than those of most single-phase BCC MPEAs. The solid solution strengthening was found to be the dominant strengthening mechanism, making up more than 90% of the yield strength of Ti40–Ti80.