The Study Of In Situ TiB₂ Particle Reinforced Cast Aluminum 101 Matrix Composite

Due to the need for environmental protection and energy-saving, lightweight vehicles has become the world trend of development of public transport. In order to save energy and improve the carrying capacity, also reduce the weight of the structural parts, it has important theoretical and practical significance to develop a new type material with high strength in stead of the traditional cast iron. And particle reinforced aluminum matrix composites possess several additional advantages such as light weight, wear-resisting, high temperature-resisting, high specific strength and modulus. So they are widely used in motor industry.The electromagnetic-mechanical stirring device which was applied to prepare in situ TiB₂ particle reinforced cast aluminum 101 matrix composite was developed, and has successfully used in mixed-salt technology. Then the paper investigated the reactive thermodynamic procession of Al-KBF₄-K₂TiF₆ and the strengthening mechanism of in-situ composite. In addition, it also researched that what is the effect of the reaction temperature, stirring speed and cooling velocity to the size and distribution of TiB₂ in the composite and obtained the reasonable technological parameter.The study shows that:1. It can restrain some slag by controlling the atomic proportion of Ti and B as 1:2.2 in the reaction system of Al-KBF₄-K₂TiF₆ and will obtain pure TiB₂ reinforce in the metal metallic melt. Using the scanning electricity microscope to analyze its microstructure, finally it is demonstrated that the TiB₂ particles are hexagonal and extremely tiny, also evenly well-distributed in the matrix and their average size is about 300nm.2. Using the LSM mixed-salt reaction has successfully prepared the in-situ TiB₂ particle reinforced cast aluminum 101 composite. And the paper determined that the reasonable reaction temperature is about 880℃and stirring speed is 700～800rpm. Meanwhile, the cooling rate is about 75～90℃/s.Compared with the matrix alloy, the tensile strength, elastic modulus, yield strength of the composite increases by 24.6%, 29.4%, 24.6%. The results of the analysis of the tensile fracture morphology indicate that the reinforcement mechanism of in-situ TiB₂ particles reinforced aluminum matrix composites as cast includes Orowan strengthening, grain-refined strengthening,dislocation strengthening.