Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering

Abstract

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.

Effects of Hot-Hydrostatic Canned Extrusion on the Stock Utilization, Microstructure and Mechanical Properties of TiBw/TC4 Composites with Quasi-Continuous Network

“…It should also be noted that there were a small number of micro-pores in the matrix and the size of them was less than 2 µm. The presence of these micro-pores would not become the starting source of the crack and therefore did not adversely affect the properties of the composites [ 20 ].…”

“…However, there was no discussion about which parts were liable to rupture. In our previous work on the TiB whisker-reinforced TA15 matrix composites [ 20 ], the TiB whiskers, whose longitudinal axes were parallel to the tensile load direction, were prone to break during the tensile testing process. In the extrusion process, the TiB whiskers whose longitudinal axes were inconsistent with the extrusion direction would twist with the flow of the matrix and this part of the whiskers was mainly subjected to shear.…”

“…So, it was less likely that this part of the whiskers would break. It could also be confirmed by the phenomenon that only the debonding between TiB whisker and matrix occurred but not the fracture of TiB whisker for the TiB whisker whose longitudinal axes were perpendicular to tensile load direction during the tensile testing process of the TiB whisker-reinforced TA15 composites fabricated by vacuum hot-pressing sintering [ 20 ]. The whiskers whose longitudinal axes were parallel to the extrusion direction were subjected to tensile stress during the extrusion process and were more prone to break.…”

High Temperature Deformation Behavior of In-Situ Synthesized Titanium-Based Composite Reinforced with Ultra-Fine TiB Whiskers

“…Titanium alloy reinforced with fibers or particles, also known as titanium matrix composites (TMCs) are commonly used in aerospace and marine industries that require their high specific strength and good corrosion resistance [ 1 , 2 , 3 ]. Generally, TiC, SiC and TiB are often used as reinforcing phases in titanium alloys, and they indeed improved the performance of titanium alloys to some extent [ 2 , 4 ].…”

Mechanical Response and Failure Evolution of 304L Stainless Steel under the Combined Action of Mechanical Loading and Laser Heating

“…With the increase of laser power density, dimples rupture (density and of the voids/cracks The development of voids is the characteristic of large deformation within the primary grain boundary. Moreover, at higher power densities, the cracks initiated in the localized region merged into each other while creating the voids of increased size [33].…”