Microstructure evolution during hot-packed rolling and mechanical properties anisotropy of as-rolled network-structured TiBw/ TA15 composites

In this study, the scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) was used to investigate the evolution of the TiB whiskers (TiBw) orientation, microstructure, and texture during hot rolling. The mechanical properties at room-temperature were tested for as-rolled composites in different loading directions. Based on the calculated and measured Schmid Factors (SFs), the effect of texture on the modes of dislocation slip in different directions was researched. A generalized shear-lag model was modified to evaluate the strengthening contribution of TiBw in different directions. The effects of matrix texture, TiBw orientation, and Hall-Petch (H-P) relationship on the anisotropy of mechanical properties of as-rolled composites were comprehensively analyzed. Results show that recrystallization (DRX) mechanisms include continuous DRX (CDRX) and discontinuous DRX (DDRX) during hot rolling. When the rolling reduction was 70%, the matrix alloy displayed the {11 2 0} <101 0> texture (the crystal c-axis point to the TD, i.e. T-Texture) and recrystallization texture. With the increase of rolling reduction, the strength of as-rolled composites increased. The best mechanical properties were obtained in the rolling direction (RD) at 60% rolling reduction, in which the tensile strength and plasticity were increased by 14% and 17.3% respectively compared with as-sintered composites. The prismatic <a> slip and the basal <a> slip were activated in RD and transverse direction (TD) respectively during room-temperature tensile. The strengthening contribution of TiBw decreases from RD to TD. Analysis of the synergistic effect of TiBw load-transfer reinforcement and H-P reinforcement on property anisotropy shows that the combination of the H-P relationship and TiBw orientation weakens the as-rolled composites anisotropy.