SiCp/A390复合材料中析出相的形貌及界面结构演变

The evolution of morphology and interfacial microstructure of precipitated phases in SiCp/A390 composites

采用快速凝固的A390铝合金粉体和SiC颗粒,通过粉末冶金法+热挤压工艺制备了SiCp/A390复合材料,并对复合材料进行了T6处理,利用扫描电镜(SEM)、透射电镜(TEM)及高分辨透射电镜(HRTEM)对复合材料时效过程中第二相的析出形貌及界面结构进行了表征,测定了复合材料的力学性能,探讨了析出相的演变规律、析出相与基体的界面结构及其对力学性能的影响。结果表明:SiCp/A390复合材料经固溶+时效处理后,合金元素从基体中析出形成GP区,然后转变为颗粒状的δ″相。随着时效时间的延长,这些颗粒状δ″相继续长大成δ'相和δ相;同时,时效析出相与基体之间界面结构随时效时间的延长发生着转变,其转变规律为:完全共格界面GP区→共格界面的δ″相→半共格界面δ'相→非共格界面δ相;SiCp/A390复合材料的抗拉强度随着时效时间延长先增加后降低,在时效6 h时,复合材料的力学性能达到最大值。

SiCp/A390 composites were prepared by powder metallurgy method and hot extrusion process using rapidly solidified A390 alloy powder and SiC particles,and then were treated with T6. The morphology and interfacial structure of the second precipitated phase during the aging process of the composites were characterized using scanning electron microscopy(SEM),transmission electron microscopy(TEM) and high resolution electron microscopy(HRTEM),and the mechanical properties of the composites were determined. Further,the evolution law of precipitated phases,the interfacial structure between precipitated phases and matrix and its influence on mechanical properties were discussed. The results indicate that the alloying elements precipitate out of the matrix and form GP zones after solid solution and aging treatment of SiCp/A390 composites,and then turn into granular δ″ phase. The granular δ″ phase grows into δ' phase and δ phase and the interfacial structure between aging precipitated phases and matrix transforms with the extension of aging time following the rule: fully coherent interface of GP zones→ coherent interface δ″ phases →half coherent interface δ' phases → incoherent interface δ phases; The tensile strength of SiCp/A390 composites increases firstly and then decreases with the extension of aging time,and the mechanical properties of the composites reach maximum at the age of 6 h.