Experimental investigation and theoretical analysis of the microstructure of thixomolded AZ91D were carried out to comprehensively understand the morphology transformation of solid particles and the solidification beh...Experimental investigation and theoretical analysis of the microstructure of thixomolded AZ91D were carried out to comprehensively understand the morphology transformation of solid particles and the solidification behavior. Typical microstructure of thixomolded AZ91D is composed of a-Mg and β-Mg17Al12, characterized with aun, aprim and eutectic. Four kinds of aun are classified according to the morphology and generation mechanism, such as spherical （al）, irregular （a2）, entrapping liquid alloy inside （a3） and entrapping pool inside （a4）. Under the effect of heating, shearing, collision, agglomeration or fragmentation, a2 and a4 can be the middle states ofal and a3. Similarly, a4 and a3 can also break into a2 and become al at the end. Controlled by undercooling, aprim nucleates and spherically grows within the remaining liquid alloy of thixomolded AZ91D until instability growth. The investigated microstructure was theoretically proved according to the analysis of Mg-Al binary phase diagram.展开更多
基金Projects (2006BA104B04-1 2006BAE04B07-3) supported by the National Science and Technology Supporting Program of China+1 种基金Project (2007KZ05) supported by the Science and Technology Supporting Project of Changchun City, ChinaProject supported by the "985 Project" of Jilin University, China
文摘Experimental investigation and theoretical analysis of the microstructure of thixomolded AZ91D were carried out to comprehensively understand the morphology transformation of solid particles and the solidification behavior. Typical microstructure of thixomolded AZ91D is composed of a-Mg and β-Mg17Al12, characterized with aun, aprim and eutectic. Four kinds of aun are classified according to the morphology and generation mechanism, such as spherical （al）, irregular （a2）, entrapping liquid alloy inside （a3） and entrapping pool inside （a4）. Under the effect of heating, shearing, collision, agglomeration or fragmentation, a2 and a4 can be the middle states ofal and a3. Similarly, a4 and a3 can also break into a2 and become al at the end. Controlled by undercooling, aprim nucleates and spherically grows within the remaining liquid alloy of thixomolded AZ91D until instability growth. The investigated microstructure was theoretically proved according to the analysis of Mg-Al binary phase diagram.
