In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs) were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs). Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the surfaces of the spherical TA15 titanium metallic powders.

The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation.

The process of TiB whiskers (TiBw) squeezed out and the growth of sticking out TiBw were investigated in TiBw/Ti-6Al-4V composites via adding 5 vol% TiB₂ powders. TiB₂ distributed along the surface of Ti-6Al-4V powders by low energy milling, resulted in the enrichment region of B and Ti elements. During sintering, TiBw nucleated and grew along the [010] direction with the diffusion of B and Ti atoms in the enrichment region. Due to larger thermal expansion ratio of TiBw, the TiBw were squeezed out from the Ti matrix, and the sticking out TiBw grew gradually with the diffusion of B and Ti atoms from the enrichment region. Because of the high interfacial strength between TiBw and Ti matrix, the matrix adhered to TiBw, and hindered the squeezing out of TiBw. Eventually, the cone TiBw stuck out the Ti matrix, and the other end of TiBw pinned in Ti matrix. Moreover, the diameter of TiBw near surface between TiB₂ and Ti matrix was larger than other areas, resulting from the high concentration of B and Ti atoms. The solubilized B atoms near TiBw were absorbed by TiBw, which was considered as the other B source of TiBw.

In this work, the influence of various rolling temperatures and thickness reductions on the dynamic recrystallization (DRX) behavior of AZ31 magnesium alloy sheets was investigated. Meanwhile, the texture variation controlled by DRX behavior was analyzed. Results suggested that, with the help of DRX behavior, reasonable matching of rolling temperature and thickness reduction could effectively refine the grain size and improve the microstructure homogeneity. Using the grain refinement and microstructure homogeneity as the reference, the critical rolling process parameters were 400 °C—30%, 300 °C—30%, and 250 °C—40% in the present work. In terms of basal texture variation, the occurrence of twins produced the largest maximum texture intensity. However, for the sheets with DRX behavior, the maximum texture intensity decreased sharply, but would steadily increase with the growth of DRXed grain. Additionally, for DRXed grains, the //RD (RD: rolling direction) grains would gradually annex the //RD grains with the growth of DRXed grains, which finally made their texture component become the dominant texture state. However, when the deformation continued, the in DRXed grains would rotate toward the RD again. Weighted by the fracture elongation of AZ31 magnesium alloy sheet, the critical thickness reductions were 30–40% under the rolling temperature of 400 °C.

AZ31 magnesium alloy sheets with 2 mm thickness were successfully fabricated by multi-pass lowered-temperature rolling. The evolution of the microstructure, texture, and mechanical properties during the rolling process was investigated. Based on the effect of multiple dynamic recrystallization, multi-pass lowered-temperature rolling not only refined the grain size obviously but also markedly improved the microstructure homogeneity. The resulting sheets had the optimal microstructure morphology with an average grain size of 4.38 μm. For the texture evolution, the stress state of the rolling process made the (0002) basal plane gradually rotate toward the rolling plane. However, the activation of non-basal slips due to the higher rolling temperature slightly rotated the (0002) basal plane point to the rolling direction (RD). As a result, the grain refinement strengthening and the texture strengthening together increased the yield stress to 202 MPa in the transverse direction (TD) and 189.8 MPa in the RD. Importantly, the resulting sheet concurrently exhibited excellent fracture elongation, about 38% in the TD and 39.2% in the RD. This was mainly ascribed to the finer grain size, giving rise to a significant effect of grain boundary sliding and the activation amount of non-basal slips.