Morphologies of Al₄Sr Intermetallic Phase and Its Modification Property upon A356 Alloys

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• 作者：Chengwei Liao ; Jianchun Chen ; Yang Li ; Rui Tu ; Chunxu Pan
• 关键词：Intermetallics ; Modification ; Hot extrusion ; Heat treatment ; Microstructure
• 刊名：Journal of Materials Science & Technology
• 出版年：2012
• 出版时间：June, 2012
• 年：2012
• 卷：28
• 期：6
• 页码：524-530
• 全文大小：1671 K

文摘

In general, the modification performance of Al-Sr master alloys is primarily dependent upon the morphologies and sizes of the Al₄Sr intermetallic phase. In this paper, the crystal structure, morphologies, sizes, hardness and elastic modulus of Al₄Sr in Al-Sr master alloys prepared from variant processes were studied by means of optical metallurgical microscope, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nanoindentation system. The results revealed that the microstructures and modification performance of the Al₄Sr phase were related to the preparation processes. That is to say, when a ¡°direct reaction-hot extrusion¡± process was used, the Al₄Sr phase exhibited a homogeneous distribution in the Al matrix with small size and roundish shapes, which ensured the Al-Sr master alloy wire advantages involving high recovery, good reproducibility, no delitescence of modification, no corrosion on equipments, and good workability. However, in the case of the traditional ¡°direct reaction¡± process, the Al₄Sr phase was in large size with shapes of rectangular stripe and plates, which limited the Sr content increasing due to the brittleness of the Al-Sr alloy It was also found that the morphology and size of the Al₄Sr phases changed during heat treatment at high temperature up to 600 ¡ãC.