Research On The Anti-oxidation Behavior And Mechanical Properties Of (TiBw+TiCp)/TC4Composites With A Novel Network Microstructure

The objective of this article is to increase the mechanical properties and high temperature oxidation resistance of titanium matrix composites (TMCs).TiC particles and TiB whiskers reinforced titanium matrix composites with a network microstructure were successfully fabricated by in situ technique, powder metallurgy method, low-energy ball milling and hot-press sintering processes based on the system of large and spherical TC4powders and fine graphite (C), titanium diboride (TiB2) powders. The characteristics of the reinforcement morphology and distribution are studied by a scanning electron microscopy (SEM). To evaluate the bending strength, tensile strength, nanohardness and elastic modulus of TMCs with different reinforcement relative contents, three-point bending, tensile test and nanoindentation testing at room temperature are carried out. The reason that the mechanical properties of TiCp/TC4composites with a network microstructure are improved by adding TiB whiskers is analyzed. High temperature oxidation resistance of TMCs with a network structure is discussed in detail. Oxidation process is analyzed by X-ray diffraction(XRD), SEM and energy dispersive spectrometer (EDS). Oxidation mechanism of TMCs with a network microstructure is summarized. The effects of reinforcements relative content on oxidation resistance is studied.The analysis of ball milling process exploration shows that the microstructure and bending properties of the composites with a network microstructure are not obviously affected by the milling process. The first milling process is that three raw materials were mixed together, and the second one is that TC4powders and the TiB2powders were mixed, and then, the mixed two powders and C powders were mixed.The research on the microstructure of the hybrid (TiCp+TiBw)/TC4composites with a novel network microstructure shows that the reinforcements distribute homogeneously around the TC4particle."TiCp wall" is formed from in situ TiCp. TiB whiskers with self-joining shapes are increased with increasing TiB volume fraction.The bending properties are obviously improved by adding TiBw reinforcement instead of TiCp reinforcement. The bending strength increases with increasing TiB volume fraction, and the bending strength and the ultimate strength of (4vol.%TiCp+2vol.%TiBw)/TC4composites with a network microstructure reach to827MPa and599MPa, respectively. Nanohardness and elastic modulus increase from the matrix center to the network boundary. The main reasons for the superior strength can be attributed to the gradinet distribution of TiB whiskers in the network structure. The novel self-joining structures of TiB whiskers are believed to be benefical to the mechanical properties.The results of high temperature oxidation resistance shows that the isothermal oxidation kinetic curves mainly follow parabolic rate law at600℃and700℃. The oxidation products are mainly consisted of rutile-TiO2and Al2O3. The oxidized "ceramic wall" can effectively join and pin the cell oxidation films, and the film/metal interface bonding strength can be effectively increased. Therefore, the hybrid (TiCp+TiBw)/TC4composites with a novel network microstructure posses superior oxidation resistance.The addition of TiB whiskers can reduce the oxidation resistance of the composites with a novel network microstructure.It is attributed to the formation of volatile B2O3.