Preparation Of Al-Ce Based Master Alloy And Its Application In ZA105 High Zinc Magnesium Alloy

As is well known that the application and popularization of Mg-Al alloy are limited by using at higher than 120℃. Recent researches found that Mg-Zn-Al alloys are considered to be a new magnesium alloys with a promising future and high temperature creep resistence because of their high temperature performance, low cost and good casting performance. However the tensile strength and impact-toughness of the alloys still remain to be further improved.The pure alloy elements join in the magnesium alloy have been intensively studied in the majority magnesium alloys studies, but in this paper the way of elements addition was broken. The master alloy is prepared with alloying elements, which not only eliminates the specific gravity differences among alloying elements but also diminishes the melting point differences. Based on the previous studies, Al, Ce, Sb, Ti are adopted as the main alloying elements and ZA105 high zinc magnesium alloy is chosen as the matrix alloy in this paper. The effects of the self-regulating master alloys on the microstructure and mechanical properties of ZA105 high zinc magnesium alloy are investigated. Al and Ce elements are rated as the main alloying elements, with Sb,Ti,Mn joined, two new type Al-Ce based master alloy are prepared, which are Al-40%Ce-5%Sb-4.8%Ti (5#) and Al-40%Ce-5%Sb-4.8%Ti-5%Mn(6#) master alloys respectively, the result shows that:The microstructure of ZA105 high zinc magnesium alloy consists ofα-Mg matrix,τ-Mg32 (Al, Zn)49,φ-Al2Mg5Zn2 and Al4Ce compound phase with 5# master alloy addition. With the increase of 5# master alloy addition, the net-like secondary phase is broken into short strip or blocks gradually and these phases evenly distribute in the matrix of alloy. The matrix of alloy becomes fine obviously too. Especially when the amount of master addition is 2.0wt.%, the secondary phases which are all small blocks distribute in the maximum dispersively. The tensile strength of the alloy at room and high temperature reach the matrix, which are 195MPa(RT),177MPa(150) and 152MPa(200℃) respectively,8.33%,18.00%and 16.92%higher than ZA105 high zinc magnesium alloy without 5# master alloy addition respectively. When the amount of 5# master alloy addition is 1.0wt.%, the impact-toughness of alloy reaches maximum, which is 8.45J/cm2,16.23%higher than ZA105 high zinc magnesium alloy without 5# master alloy addition. With the further addition of 5# master alloy in ZA105 high zinc magnesium alloy, a needle-like phase appeared. The uniformly distributed secondary phases gradually joined together by the needle-like phase and form a long strip or broken net-like phase. Meanwhile, the needle-like phase also seriously dissevers the matrix and reduces the tensile strength at room and high temperature of the alloy, especially the impact-toughness. The hardness of ZA105 high zinc magnesium raises with the increase 5# master alloy addition due to the increase of hard particle phase in the alloy all the time.The matrix and secondary phases of ZA105 high zinc magnesium alloy change a lot with the increase of 6# master alloy addition, as similar as the alloy with 5# master alloy addition. But when the amount of 6# master alloy addition is 3.0wt.%, the secondary phases which are all blocks distribute in the matrix, the matrix is also refined apparently and the tensile strength and impact-toughness all reach maximum, which are 198MPa(RT),178 MPa(150℃), 155MPa(200℃) and 9.21 J/cm2 respectively,18.67%,10.00%,19.23%and 26.69%higher than the alloy without 6# master alloy addition. With the amount of 6# master alloy addition increasing, the microstructure and the mechanical properties(the tensile strength and impact-toughness) of ZA105 high zinc megnisium alloy are the same as the alloy with 5# master alloy addition, the hardness of the alloy is also improved with the increase of 6# master alloy addition.Contrasting the effect of 5# and 6# master alloy on the microstructure and mechanical properties of ZA105 high zinc magnesium alloy, found that the improvement of 6# master alloy on the secondary phases of ZA105 high zinc magnesium alloy is superior to that of 5 master alloy, especially the mechanical properties. The tensile strength at room and high temperature of ZA105 high zinc magnesium alloy with 6# master alloy addition is better than that with 5# master alloy addition, especially the impact-toughness, which is 10.46%higher than the alloy with 5# master alloy addition. However, the hardness is slightly lower than that with 5# master alloy addition.