Copper / Steel Compound Plate Dip Aluminum Take Aluminum / Steel Composite Casting And Its Interfaces

Al/st. composite casts were successfully produced by inserting an explosively welded Cu/st. composite plate into aluminium melt. The microstuctures of Al/st. interface were investigated and its bonding strength was tested as well. The bonding mechanism of the interface, the cause of the high bonding strength and other related questions are discussed.The results showed that copper plate formerly welded on the steel plate has been dissolved into alminium melt totally, and the Al/st. interface after casting remained to be undular like the Cu/st. interface after explosively welding. Continuous intermetallic layer with a thickness about 20 m appeared on the Al/st. interface and a lot of blocklike phases existed in the aluminium matrix near the interface. The results of element area scanning and powder x-ray spectra revealed that the continous intermetallic layer comprised two different layers, of which the one near steel was Fe2Als and the other was FeAla. The blocklike phases were also identified as FeAls and their formation was supposed to be related with the infiltration of the aluminium melt along the steel grain boundary. Due to the great difference of thermal expansion between the matrix and the intermetallic layers, a lot of cracks were found in the Fe2Al5 layer at the ridge. When the specimen was cooled in air after annealing, the cracks were propagated to the trough, crest and the blocklike phases.The bonding strength of Al/st. interface reached 80.5MPa, which was identified by tensile-shear test. The investigation of the fracture surface showed that the brittle part happened at the ridge and the plastic one at the trough and crest. The wave crest and trough separated the cracks at interface and impeded the propagation of cracking, which might increase the bonding strength of Al/st. interface.