SiCp颗粒含量对SiCp/ Mg–5Al–2Ca复合材料组织与性能的影响

Effects of SiCp content on the microstructure and mechanical properties of SiCp/Mg–5Al–2Ca composites

摘要:

本研究通过搅拌铸造法制备了三种不同体积分数(2%,5%, 10%)的SiCp/Mg–5Al–2Ca复合材料,并在673 K下进行了热挤压。铸态复合材料中,少量SiCp颗粒的加入就能破坏了Al₂Ca相沿基体合金晶界分布并有效细化Al₂Ca相析出尺寸。随着SiCp体积分数的增高,Al₂Ca相尺寸有所降低,但不明显。经过热挤压后,Al₂Ca相破碎并沿挤压方向排布,基体合金晶粒得到细化。晶粒尺寸以及Al₂Ca相尺寸随着SiCp体积分数的增高呈微小降低。与单组元基体合金相比较,挤压态SiCp/Mg–5Al–2Ca复合材料的屈服强度和加工硬化率随着SiCp体积分数的增高而逐渐增高,而延伸率则逐渐下降；抗拉强度最大值则出现在SiCp体积分数为5%时。复合材料中SiCp颗粒以及Al₂Ca相的脱粘以及开裂是导致复合材料断裂的主要原因。

Abstract:

The Mg–5Al–2Ca alloys reinforced by 2 vol.%, 5 vol.% and 10 vol.% 5μm SiCp were fabricated by stir casting. The cast composites were subject to hot extrusion. In the cast composites, addition of SiCp disturbs the network distribution of Al₂Ca phase along grain boundaries. After extrusion, grains of the matrix are refined further and the Al₂Ca phase broke into particulates. Moreover, the Al2Ca phase and grain size can be further refined by the addition of SiCp. As compared with monolithic Mg–5Al–2Ca alloy, the addition of SiCp conduces to obvious improvement of TYS and work hardening rate, however, at the expense of elongation. Unlike the TYS, the UTS of SiCp/Mg-5Al-2Ca composite does not change monotonously with increasing SiCp’s content, the highest UTS appears when the SiCp’s volume fraction is 5%. The interfacial debonding between SiCp and Al₂Ca phase and cracked particles are considered as the main crack source for SiCp/Mg–5Al–2Ca composite.