Bimodal grain size structure design to optimize the mechanical properties of TiZrNbTa high entropy alloys/Ti composites

Grain refinement is perfectly efficient for improving strength, but accompanies by a dramatic loss of ductility. Here we report a bimodal grain size structure design by inducing ultra-high strength TiZrNbTa high entropy alloy (HEA) with nanoscale grain size into pure Ti with coarse grain size to achieve the strength-strain balance by establishing bimodal grain size distribution (BGSD). Through optimizing the TiZrNbTa HEA content, the 60 wt.% TiZrNbTa/Ti titanium matrix composite (TMC) exhibits a yield strength of 1426 ± 30 MPa, ultimate compressive strength of 2133 ± 88 MPa, and an acceptable compressive strain of 22.3% ± 1.8%, respectively. The compressive yield strength of 60 wt.% TiZrNbTa/Ti TMC is 3.6-fold for c.p. Ti (393.0 ± 7.1 MPa). The unusual high strength is attributed to the nanoscale grain size provided by TiZrNbTa HEA, and the acceptable compressive strain is obtained from the co-effect of coarse grain Ti and TiZrNbTa HEA. The excellent mechanical properties of 60 wt.% TiZrNbTa/Ti TMC undoubtedly greatly increase the possibility of its application as an orthopedic implant in the biomedical field.