The Study Of (TiB₂+Al₃Ti)/ZL101 In Situ Composite

The synthetic technology of in situ composites is that a kind of new type material preparing technology. In-situ composites have excellent mechanical properties comparing with the composites in which the reinforcing phase is added by outside. In this paper, (TiB₂+Al₃Ti)/ZL101 in situ composites have been manufactured by the method of solid-liquid reaction. The selection and formation thermodynamics of reinforcing phase, the relationship between matrix and reinforcing phase and reinforcing mechanism have been studied carefully. The microstructures, phase configurations and the distribution of the reinforced phase (TiB₂+Al₃Ti)/ZL101 in situ composite have been studied by means of analysis of TEM method. The mechanical properties of the composite have also been tested. The morphology of microstructure has been characterized by metallographic microscope, scanning electron microscope, transmission electron microscope (TEM). The main results are as follows:(1) According to the orthogonal experimental result and considering the best combination for the properties of tensile strength and ductility, experimental result is analyzed by orthorhombic experimental analysis. Three levels and four factories orthogonal experiment show that the composition of this composite is defined as 1%TiB₂, 5%Al₃Ti, and the temperature of melting are 1000℃.(2) The tensile strength, the ductility and the hardness of (TiB₂+Al₃Ti)/Z101 in situ composite after heat treatment are 323MPa, 4.7% and 121HB, and the increasing rate are 23.3%,14.6%and23.5% respectively in comparison with those of ZL101 matrix.(3)Microstructure analysis shows that the grain size ofα-Al and eutectic Si of (TiB₂+Al₃Ti)/Zl101 in situ composite is smaller than that of ZL101 matrix. After heat treatment, all eutectic Si grain is changed into particle and its size is about 5μm. But the eutectic Si grain of ZL101 matrix is partly changed to particle and its size is about 15μm.(4)TEM analysis shows that the shapes of TiB₂ and Al₃Ti are particle and rod. The in-situ reinforcing phases are distributed uniformly in the matrix and the interface withα-Al is good combination, and they demonstrate remarkable grain-refining effect on the matrix.(5)The reinforcing mechanism for the in-situ composites of (TiB₂+Al₃Ti)/ZL101 is fine-grain reinforcing, solution reinforcing, dispersion reinforcing and dislocation reinforcing.