The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with t...The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with the amount of Ca added to the melt.The optimal microstructure and properties were obtained by adding 0.06 wt%Ca to Al-7 Si-0.3 Mg alloy.The secondary dendrite arm spacing(SDAS)of the primaryαphase decreased from 44.41μm to 19.4μm,and the eutectic Si changed from coarse plates to fine coral.The length of the Fe-rich phase(β-Al5 Fe Si)decreased from 30.2μm to 3.8μm,and the Brinell hardness can reach to 66.9.The ultimate tensile strength,yield strength,and elongation of the resulting alloy increased from 159.5 MPa,79 MPa,and 2.5%to 212 MPa,86.5 MPa,and 4.5%,respectively.The addition of Ca can effectively refine the primaryαphase and modify the eutectic Si phase,likely because Ca enrichment at the front of the solid-liquid interface led to undercooling of the alloy,reduced the growth rate of the primaryαphase,and refined the grain size.Also,it could increase the latent heat of crystallization,undercooling,and the nucleation rate of eutectic Si,which was beneficial to the improvement of the morphology of eutectic Si.展开更多
基金financially supported by the National High-tech R&D Program of China (No. 2014AA041804)International S&T Cooperation Program of China (No. 2014DFA53050)
文摘The effect of Ca addition on the elemental composition,microstructure,Brinell hardness and tensile properties of Al-7 Si-0.3 Mg alloy were investigated.The residual content of Ca in the alloy linearly increased with the amount of Ca added to the melt.The optimal microstructure and properties were obtained by adding 0.06 wt%Ca to Al-7 Si-0.3 Mg alloy.The secondary dendrite arm spacing(SDAS)of the primaryαphase decreased from 44.41μm to 19.4μm,and the eutectic Si changed from coarse plates to fine coral.The length of the Fe-rich phase(β-Al5 Fe Si)decreased from 30.2μm to 3.8μm,and the Brinell hardness can reach to 66.9.The ultimate tensile strength,yield strength,and elongation of the resulting alloy increased from 159.5 MPa,79 MPa,and 2.5%to 212 MPa,86.5 MPa,and 4.5%,respectively.The addition of Ca can effectively refine the primaryαphase and modify the eutectic Si phase,likely because Ca enrichment at the front of the solid-liquid interface led to undercooling of the alloy,reduced the growth rate of the primaryαphase,and refined the grain size.Also,it could increase the latent heat of crystallization,undercooling,and the nucleation rate of eutectic Si,which was beneficial to the improvement of the morphology of eutectic Si.
