Microstructure evolution and high-temperature tensile behavior of the powder extruded 2.5 vol% TiBw/TA15 composites

In this paper, 2.5 vol% TiBw/TA15 composites were fabricated by low-energy milling and subsequent powder extrusion. After low-energy milling process, the fine TiB2 powders were adhered on the surface of the spherical TA15 powders. Next, the blended powders were extruded at 1100 degrees C with extrusion ratio of 10:1. The Widmanstatten alpha + beta microstructure with thickness of 550-620 run in alpha phase was obtained and the strong (0001)(alpha)//ED and (101)(alpha)//ED texture was formed after powder extrusion. The TiB whiskers (TiBw) twisted along the extrusion direction and led to the 'wall' structure. High-temperature tensile behavior of this studied composites was investigated at 800-950 degrees C with strain rate of 0.001-0.1 s(-1). According to the stress-strain curves, the activation energy (Q) was calculated to be 325 kJ mol(-1), higher than the TA15 matrix, which is due to the combined effect of phase morphology, extrusion texture and TiBw reinforcements. In addition, the tensile strain has effect on microstructure evolution. Static spheroidizing has been processed in the grip area of tensile sample. As the tensile strain increased, the volume fraction of and the average grain size a phase decreased. Moreover, voids nearby the TiBw reinforcements were observed due to the incoordination deformation between TiBw and TA15 matrix.