Insight into the formation mechanism and interaction of matrix/TiB whisker textures and their synergistic effect on property anisotropy in titanium matrix composites

Abstract

Considerable studies on processed pure titanium and titanium alloys have proved the possibility of property anisotropy induced by crystallographic textures, but limited information is available for the intrinsic coupling of matrix and reinforcement textures and their synergistic effect on property anisotropy in titanium matrix composite (TMCs). In the present work, an advanced EBSD/EDS coupling method was used to investigate the formation mechanism of primary α and secondary α textures in the matrix alloy. It is revealed for the first time that the reinforcement TiBw displays a {100}〈010〉 texture after hot rolling and has little effect on the matrix texture component but weakens texture intensity. Significant anisotropies in the tensile strength and ductility can be all noted at room and high-temperatures, which is the synergistic effect of the matrix texture and the aligned TiBw. The mean Schmid factor of each slip system was calculated to evaluate the influence of matrix texture on the minimum active stress of slip deformation in the different tensile directions. The analysis shows that the strong T-type matrix texture results in higher strength but lower ductility when loaded in the transverse direction. Moreover, a generalized shear-lag model was modified to quantitatively evaluate the strengthening contribution of aligned TiBw, which decreases with increasing off-axis angle and test temperature. A new parameter, defined as the critical aspect ratio of the off-axis whisker, was proposed to rationalize why the TiBw failure mechanism converts from TiBw fracture to TiBw/matrix interfacial debonding with increasing off-axis angle and test temperature.