Preparation Of TiC/7075Al Matrix Semi-solid Billet

It is studied that the TiC/7075 Al matrix Semi-solid billet was fabricated by in-situ reactive Near-liquidus method.The course of reaction of Al-C-Ti,microscopic morphology were studied by using Optical microscope,X-ray,TEM etc.The influences of the process parameters such as prefabricated blocks C/Ti molar ratio, aluminum melt temperature, Al content, pouring temperature and other factors were investigated. To determine the appropriate experimental parameters and get the better Semi-solid organization .The thermodynamic calculation shows that : The adiabatic temperature Tad come to 2343K>1800 K of Al-Ti-C system,show that the in-situ reactive can be happened and stabled.In the Al-Ti-C system in-situ synthesis of TiC particle reaction mechanism is:External heat source so that between Ti and Al to generate the response Al3Ti occurs first, followed by the exothermic reaction caused Al3Ti and C and between Ti and C to form TiC reaction.The results show that the optimal process parameters are as follows:①When the prefabricated block C/Ti molar ratio of 1.25:1,aluminum melt temperature reached 950℃,in-situ reaction occurred,Al content of 35%(mass %), the reaction completely, only to generate TiC particles;②The Temperature of Near-liquidus casting choice for the 635℃~650℃, and the better Semi-solid organizations can be obtained;③The addition of Mg powder shortened the induction time in situ reaction, so the response is faster, the test to add the amount of Mg powder is 1/300 of the total weight is more appropriate;④The Semi-solid organizations of in-situ reaction Near-liquidus casting TiC/7075Al matrix found that Near-liquidus casting 7075 Al has the typical rose-like organization, with the increasing of in-situ TiC particles content, the number of equiaxed grains organization increased, rose-shaped grains decreased, gradually to the alloy of nearly spherical transforming equiaxed grains.When TiC come to 6.0%,equiaxed grains average size with 54.4μm can be obtained.