Research on Three-Roll Screw Rolling Process for Ti6Al4V Titanium Alloy Bar

The effects of both the microstructure and the original grain size on three-roll screw rolling process of Ti6Al4V titanium alloy bar were studied in the present work. The microstructure of Ti6Al4V titanium bar had a great influence on the mechanical properties of the rolling bar. When the original size was large, the grains were apparently refined but the microstructure was uneven. But for semi-finished titanium bar composed of fine equiaxed grains, the grains after rolling were fine and uniform. During the rolling process, the Ti6Al4V titanium alloy microstructure changed from equiaxed structure to the basket-weave one. After annealing at 800 degrees C for 1.5 hours and then cooling in air, the average tensile strength decreased from 984 MPa to 964 MPa; while after annealing at 950 degrees C for 1.5 hours and then cooling by water, and aging at 540 degrees C for 6 hours then cooling by air, the average tensile strength increased from 979 MPa to 1107 MPa.