挤压温度对高硅铝合金材料组织与性能的影响

Effect of extrusion temperature on microstructure and properties of high-silicon aluminum alloy

针对应用广泛的低密度、低膨胀、高热导、高比强的高硅铝合金,采用空气雾化水冷与真空包套热挤压工艺相结合的方法,制备了Al-30Si与Al-40Si过共晶高硅铝合金材料,并通过金相微观组织分析、力学性能检测及拉伸试样断口扫描,研究了不同热挤压温度对合金的组织形貌与性能的影响.结果表明:所制备的高硅铝合金材料组织十分细小且Si相均匀弥散分布,随着挤压温度的升高,硅相晶粒增大,挤压温度在370℃～490℃范围内,硅晶粒长大不十分明显,但超过此温度区间有一个明显长大的过程;抗拉强度随挤压温度的升高、合金中Si含量的增加及原始粉末粒度的增大而下降;随着挤压温度的升高,合金材料的断裂方式由韧性断裂方式过渡到韧性与脆性共存的混合断裂方式.

High-silicon aluminum alloy is a widely applied material possessing low density, low thermal expansion coefficient, and high thermal conductivity. In this study, Al-30Si and Al-40Si hypereutectic high-silicon aluminum alloy were fabricated with a method in which air-atomization was followed by vacuum canning hot-extrusion process. Effect of extrusion temperature on microstructure and properties was discussed by means of optical microscopy, SEM fracture surface analysis, and tensile strength testing. Experimental results indicate that, silicon crystal is fine and evenly distributed in the matrix, its particle size increases with the increase of extrusion temperature-grain growth is not obvious in 370℃ --490℃ temperature range. Tensile strength decreases with the increase of extrusion temperature, silicon content and particle size of starting powder. The fracture mode of the material changes gradually from tough fracture mode to a mixture of tough and brittle ones with the increase of extrusion temperature.