Effect Of Grain Refine On Microstructure And Mechanical Property Of ZLSi7Cu2Mg Alloy

ZLSi7Cu2 Mg alloy is widely used in the engine cylinder and lid with small density、corrosion resistance and good casting properties. With the progress of science and technology, the development of industry put forward higher properties requirement in engine cylinder and lid, simply by changing the composition is hard to improve the overall property of the material, therefore, we need to increase mechanical properties of the material by grain refinement.In this paper, ZLSi7Cu2 Mg alloy as the research object, through the orthogonal experiment respectively change the addition amount、pouring temperature and holding time of Al-5Ti-0.3Cand Al-5Ti-0.6B-0.2C master alloy in ZLSi7 Cu2Mg alloy, compare the different experimental scheme effects on microstructure refinement、mechanical properties and SDAS of ZLSi7 Cu2Mg,determine the best experimental plan,on the basis of the research studied the refinement mechanism.The main research content is as follows:(1)Refining of the Al-5Ti-0.3C master aloy on ZLSi7Cu2 Mg aloy.The main second phases of Al-5Ti-0.3C master alloy is TiC, as the heterogeneous nucleation core of α-Al, it can refine the microstructure and reduce the SDAS of ZLSi7Cu2 Mg al oy.The mechanical properties of ZLSi7 Cu2Mg alloy is better after refining with Al-5Ti-0.3C. Compare with the original state, the tensile strength 12.5% increase and the elongation 36.9% increase.(2)Refining of theAl-5Ti-0.6B-0.2Cmaster aloy on ZLSi7Cu2 Mg aloy.The main second phases of Al-5Ti-0.6B-0.2Cmaster alloy include TiC doped with trace B and TiB2, the two kinds of particles are dispersed in the matrix, as the non-spontaneous nucleation of α-Al, it can obviously refine the microstructure and reduce the SDAS of ZLSi7Cu2 Mg al oy.The mechanical properties of ZLSi7 Cu2Mg alloy is better after refining with Al-5Ti-0.6B-0.2C. Compare with the original state, the tensile strength 16.7% increase and the elongation 52.1% increase. Under the same conditions, the refinement with Al-5Ti-0.6B-0.2C is better than with Al-5Ti-0.3C. This is because doped with trace B, nucleation particles increases and makes the TiC particles is more stable, so that the refinement is enhanced.