热处理对汽车用镁/铝复合板的扩散动力学及力学性能的影响

Effect of Heat Treatment on the Diffusion Kinetics and Mechanical Properties of Mg/Al Composite Plates for Vehicles

目的探明热处理工艺参数对镁/铝复合板界面金属间化合物(IMCs)生长的影响规律,并揭示IMCs对镁/铝复合板力学性能的影响。方法首先通过热轧复合实验,制备了镁/铝复合板,其次通过不同的热处理工艺以及对界面微观结构特征的表征实验研究了温度和时间对镁/铝复合板界面金属间化合物和界面结合质量的影响规律,最后通过理论计算,从扩散动力学的角度分析了界面相的形成机制和长大行为。结果镁和铝之间反应主要生成2种金属间化合物,即靠近铝侧的Mg_(2)Al_(3)和靠近镁侧的Mg_(17)Al_(12);一定厚度的金属间化合物有利于界面结合强度的提高,其中当IMCs层厚度为4μm时,界面结合强度最高,为32.5 MPa,随着IMCs层厚度的增加,界面结合质量逐渐降低,最终稳定在12.4 MPa附近。结论界面结合强度变化主要是由于热处理改变了界面的结合方式,由最初的Mg-Al直接接触到不连续的Mg-IMCs-Al接触再到最后的连续的Mg-IMCs-Al接触,改变了界面裂纹萌生和失效的方式。

The work aims to explore the effect laws of heat treatment process parameters on the growth of intermetallic compounds(IMCs)at the interface of Mg/Al composite plates and reveal the effect of IMCs on the mechanical properties of Mg/Al composite plates.The Mg/Al composite plate was firstly prepared through hot rolling composite experiments,and then the effect laws of temperature and time on the interfacial intermetallic compounds and interfacial bonding quality of the Mg/Al composite plate were investigated through different heat treatment processes as well as experimental characterization of the interfacial microstructural features,and finally the formation mechanism of the interfacial phases and the growth behaviors were analyzed through theoretical calculations in the viewpoint of the diffusion kinetics.Two main IMCs,Mg_(2)Al_(3) near the Al side and Mg_(17)Al_(12) near the Mg side,were formed through the reaction between Mg and Al.A certain thickness of IMCs was beneficial to improving the interface bonding strength.The highest bonding quality of 32.5 MPa was achieved when the thickness of the IMCs layer was 4μm.As the thickness of the IMCs layer continued to increase,the bonding quality gradually decreased and stabilized around 12.4 MPa.The change in interface bonding strength is primarily due to the alteration of the bonding mode at the interface caused by heat treatment.Initially,there is direct contact between Mg and Al.Then,it transits to intermittent contact between Mg-IMCs-Al,and finally to continuous contact between Mg-IMCs-Al,affecting the initiation and failure mechanisms of interface cracks.