In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase...In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase.Microstructure and morphology of Mg_(2)Si were observed by synchrotron X-ray to-mography and TEM,and first-principles calculations were also performed to testify the effect of Eu mod-ification.Results show that the size of primary Mg_(2)Si particles decreases and eutectic Mg_(2)Si phase trans-forms from lamellar to fibrous by Eu addition.After heat treatment,sharp angles of primary Mg_(2)Si par-ticles passivate,and eutectic Mg_(2)Si dissolves and appears to be short dot-like.Meanwhile,nano-sizedβ"phase precipitates in the matrix.For morphology of Mg_(2)Si with Eu modification,TEM results show that Eu impedes the growing of Mg_(2)Si,which is verified by first-principles calculations that Eu atom preferentially adsorbs on Mg_(2)Si{100}facet.The adsorption and suppression growing of Mg_(2)Si transform the morphology of Mg_(2)Si and thus improve the elongation.UTS and elongation of the heat-treated Eu modified composites are 281 MPa and 8.4%,which improved 81%and 200%compared to the as-cast Al-15%Mg_(2)Si composite.The strengthening mechanism mainly results from precipitation strengthening of nano-sizedβ"precipitates in the heat-treated composite.展开更多
基金the National Natural Science Foun-dation of China(No.U21A2042)the National Science Fund for Distinguished Young Scholars of China(No.51825401).
文摘In order to improve mechanical properties of Mg_(2)Si/Al composites,Eu element was added to mod-ify Mg_(2)Si morphology,and T6 heat treatment was used to control Mg_(2)Si morphology and precipitate strengthening phase.Microstructure and morphology of Mg_(2)Si were observed by synchrotron X-ray to-mography and TEM,and first-principles calculations were also performed to testify the effect of Eu mod-ification.Results show that the size of primary Mg_(2)Si particles decreases and eutectic Mg_(2)Si phase trans-forms from lamellar to fibrous by Eu addition.After heat treatment,sharp angles of primary Mg_(2)Si par-ticles passivate,and eutectic Mg_(2)Si dissolves and appears to be short dot-like.Meanwhile,nano-sizedβ"phase precipitates in the matrix.For morphology of Mg_(2)Si with Eu modification,TEM results show that Eu impedes the growing of Mg_(2)Si,which is verified by first-principles calculations that Eu atom preferentially adsorbs on Mg_(2)Si{100}facet.The adsorption and suppression growing of Mg_(2)Si transform the morphology of Mg_(2)Si and thus improve the elongation.UTS and elongation of the heat-treated Eu modified composites are 281 MPa and 8.4%,which improved 81%and 200%compared to the as-cast Al-15%Mg_(2)Si composite.The strengthening mechanism mainly results from precipitation strengthening of nano-sizedβ"precipitates in the heat-treated composite.
