(華南理工大學 國家金屬材料近凈成形工程技術研究中心，廣州 510640)
摘 要: 研究局部擠壓慢壓射A356壓鑄件不同部位處的微觀組織及沖擊性能。結(jié)果表明：鑄態(tài)下共晶Si粒子大多為纖維狀或長針狀，呈不均勻的網(wǎng)狀分布，沖擊吸收功在1.17~2.35 J的范圍內(nèi)變化后；經(jīng)T6熱處理后，團簇狀Al-Si共晶相明顯減少，共晶Si粒子呈現(xiàn)出粒狀或短棒狀，且細小均勻，Si粒子的長寬比和面積分數(shù)都有顯著降低，沖擊吸收功在1.45~3.80 J的范圍內(nèi)變化，比鑄態(tài)有明顯提高。分析2種情況下不同部位處的斷裂方式，數(shù)學回歸分析表明，沖擊性能由二次枝晶間距和Si粒子長寬比共同決定。
關鍵字: A356壓鑄件；慢壓射壓鑄；微觀組織；沖擊性能
（State Engineering Research Center for Metallic Materials Net-shape Processing,
South China University of Technology, Guangzhou 510640, China）
Abstract:The microstructures and impact properties of slow injection A356 die casting with partial squeeze were investigated. The results show that as for the as-cast castings, eutectic Si particles are characterized as fibrous or long acicular shape as well as in homogenous distribution, and the impact absorbed energy varies from 1.17 to 2.35 J. After T6 heat treatment, the eutectic Si particles become small granular or short bacilliform, and the aspect ratio and area fraction of Si particles decrease evidently. The energy of the T6-treated castings is 1.45−3.80 J, which is higher than that of the as-cast castings. Furthermore, the fracture mechanisms of different regions in the castings were analyzed and discussed. Through mathematical regression analysis, it is indicated that the impact property depends on both the aspect ratio and secondary dendrite arm spacing of the Si particles.
Key words: A356 casting; slow injection die casting; microstructure; impact property
