Mechanical properties and fracture behavior of Al(111)/MgAlB₄(0001) interface in Al matrix composites: a first-principle calculation study

Abstract

Hexagonal crystal MgAlB4 is a strengthening phase in Al matrix composites, which can excellently improve ultimate tensile strength. In this paper, the surface perform, interfacial bonding characteristic, fracture mechanism, and electronic properties of the Al(111)/MgAlB4(0001) interface were thoroughly investigated by the first principles method. The results reveal that the OT site and MT site configurations were more unstable than the HCP stacking. Besides, from the calculated results of interfacial energy and work of adhesion, the HCP stacked Al(111)/B(Al)-terminated/MgAlB4(0001) interface expresses stronger stability than other interfacial models, this mainly attributes to higher work of adhesion and lower interfacial energy of the HCP stacked Al(111)/B(Al)-terminated/MgAlB4(0001) interface. Analysis of electronic structure reveals that the Al-termination and Mg-termination Al(111)/MgAlB4(0001)interface presents Al-Al and Al-Mg metallic bonds at the interface, respectively, but the B(Al)-termination Al(111)/MgAlB4(0001)interface expresses strong Al-B covalent bonds characteristic, which leads to the highest interface stability. The results of tensile fracture revealed that the HCP stacked B(Al)-termination interface transferred the external stress to Al bulk, due to the Al-B covalent bond formed near the interface. Therefore, ceramic phase MgAlB4 can effectively promote the particle reinforcement of Al matrix composites.