Effect of Ga on the Microstructure and Mechanic Al Properties of AZ81 Alloy
The effect of Ga on the microstructure and mechanical properties of Mg-8wt.%Al alloy at room temperature were investigated by SEM and X-ray analysis. The microstructure of as-cast Mg-8wt.%Al alloy was consist of α-Mg matrix, β- Mg17Al12 and α+β eutectic phases. The primary β- Mg17Al12 phase precipitate along the α-Mg matrix grain boundary and in the discontinuous reticular shape. Ga addition in the as-cast Mg-8wt.%Al alloy change the microstructure significantly. When the addition is less then 2% Gd could be detected and distributed mainly within β- Mg17Al12 phase and in the interface of α-Mg matrix and β- Mg17Al12. With increasing Ga content α-Mg matrix grains and β- Mg17Al12 phase are refined. The amount of α+β eutectic structure increase as well. The holes within β phase are diminished. When Ga content was more than 2% with increasing of Ga content β phase was broken along the concentration of Ga. With the increase of Ga content to 4%, a new phase of Ga2Mg form in the microstructure and β phase precipitate in the shape of smooth baboon along the grain boundary. The mechanical properties test showed that as-cast Mg-8wt.%Al-2wt.%Ga alloy has the optimum combination of ultimate tensile strength of 248 MPa and elongation of 10%.
Zhong Wei Gu, Yafang Han, Fu Sheng Pan, Xitao Wang, Duan Weng and Shaoxiong Zhou
J. Sun et al., "Effect of Ga on the Microstructure and Mechanic Al Properties of AZ81 Alloy ", Materials Science Forum, Vols. 610-613, pp. 884-891, 2009