| Metal matrix composites have been widely utilized in aerospace,electronics, automotive and other industries with a broad space for developmentand application prospects. Taking steel as matrix, aluminum as reinforcement,steel/Al laminated composites have been fabricated endowing the two materialswith both high strength, high hardness, excellent electrical and thermalconductivity of steel and superior wear resistance, ductility, corrosion resistance,low specific gravity and tidy surface performance of Al, which obtain aeconomical efficiency and admirable comprehensive performance with a broaddevelopment prospects.However, due to the significant difference of melting point, thermalexpansion coefficient and mechanical properties of steel and aluminum, parts ofnon-continuous brittle metal compounds such as FeAl, FeAl2and FeAl3wouldemerge between the two contact surfaces after hot combination following withannealing in a high temperature, which cause the deterioration of themechanical properties of the composites seriously. Nowadays, the maintechniques that are available for the preparation of steel/Al composite materials include solid-phase welded method, plastic processing method, adhesionprocess and other techniques.In this study, two methods were used to inhibit the brittle intermediatecompounds. One of the methods was to manufacture steel/Al plates directly bytwo-pass hot rolling on purpose of crashing the intermediate compounds with ahigh temperature and large reduction. It was found that during the first-passrolling, there was no intermetallics presented at the interface, afterwards, partsof continuous or non-contiguous Fe-Al intermetallics such as FeAl, FeAl2andFeAl3produced at the interface after heated at600℃for a while, the existenceof these intermetallics became the main initiation areas of crack, which couldpromote the crack propagation and thus reduced the anti-punching performanceof the laminated composites. However, all these intermetallics would be crashed,pulled away from each other and eventually disappeared in the matrix by a largereduction during the second-pass hot rolling. As a consequent, the atoms withinthe matrix would contact each other, forming a strong metallurgical bonding.What’s more, the low-temperature annealing after the second-pass hot rollingwould eliminate the internal residual stress, dislocation and inhomogeneity ofthe tissue, thus improving the stamping crack resistance, which is appropriate toutilize in low temperature periodically. The other method was to fabricate steel(Q235)/Cu/Al (5052) laminated sheets by adding thin Cu sheet into the interfaceof steel/Al sheet in order to inhibit the formation of Fe-Al brittle compoundsand improve the binding property. The manufacturing process in detail was as following: Firstly, Cu/Al sheets were rolled together until0.4mm thickness,subsequently, Al/Cu sheets were clad-rolled together with Q235steel sheet witha reduction of40%after heated at a low temperature following with heatpreservation, afterwards, series of different reductions were conducted by asecond-pass hot rolling after heated at high temperature followed by ahigh-temperature annealing. The results showed that there were threecontinuous gradient diffusion layers distributed on the interface, Al2Cu, Al4Cu9and Cu. All these intermediate layers were tightly combined with matrix,endowing with a bending cycle of45times without crack on the interface,which is suitable for application in high temperature repeatly.Furthermore, the growth of the intermetallics has certain regularity, thediffusion extension and growth rate of the intermetallics improve with theincrease of annealing temperature and time. None of the intermetallics can beobserved on the interface even with the prolongation of annealing time at a lowtemperature. The interface morphology of the steel (Q235)/Al (5052) plates wasobserved by SEM, the interface morphology of the steel (Q235)/Cu/Al (5052)sheets was analyzed by EBSD techniques. |
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