Effects of annealing and cold roll-bonded interface on the microstructure and mechanical properties of the embedded aluminum-steel composite sheet

Embedded aluminum-steel composite sheets used in heat exchanger were produced by cold roll bonding(CRB). The influences of annealing temperature and annealing time on the microstructure and the bonding strength of the composite sheet were investigated. The recrystallization of the steel layer began at 525℃ and finished at 600℃. With the increase of the annealing temperature, the peel strength of the composite sheet whose original steel sheet surface was treated by scratch brush initially increased and then decreased, which was resulted from the competition of the mechanical locking and metallurgical bonding. After annealing, the cracks which formed between the broken work-hardened steel surface layer and its matrix during cold roll bonding remained. The composite sheet produced by CRB with the steel surface treatment of flap disc had less interfacial defects, higher bonding quality, higher diffusion rate of Al and Fe atoms at the interface and larger metallurgical bonding extent than the composite sheet produced by CRB with the steel surface treatment of scratch brush under the same conditions of annealing,which was helpful to shorten annealing time, reduce energy consumption and improve production efficiency.

嵌入式铝/钢带材轧制复合铝层和钢层厚度的变化规律

采用冷轧复合法制备嵌入式铝/钢复合带材,研究了嵌入式铝/钢带材冷轧复合压下率、铝带初始厚度对轧制复合变形区内铝层和钢层厚度比变化的影响规律;采用切片法计算变形区内界面剪切应力分布,分析了铝层和钢层厚度比变化的原因。结果表明:在特定压下率(r_(con))条件下,从轧制入口到出口变形区铝层与钢层厚度比呈先减小后保持基本不变的变化趋势;当压下率r<r_(con)或r>r_(con)时,铝层和钢层厚度比(RA/S)呈先减小后增加的变化趋势;当初始铝带厚度由0.50 mm减小至0.10 mm时,r_(con)由45%减小至30%;随着压下率的增加,变形区界面剪切应力增大,该剪切应力使铝层与钢层之间发生相对滑动(r<r_(con))、无相对滑动(r=r_(con))和粘着流动(r>r_(con));仅当压下率r>r_(con)时,拉伸断口铝层与钢层不分层,复合带材具有良好的界面结合状态。