提出了瞬时脉冲电流对铝合金超快固溶和后续时效强化的处理方案,采用宏微观实验手段分析了材料力学性能和微观组织演变规律.结果表明:随着放电电压的增大,预拉伸后7075铝合金材料屈服强度逐渐减小,但延伸率呈现"小幅度增大—减小—大幅度增大"的变化趋势.当脉冲电流峰值超过86 kA(对应的放电电压超过9 kV)时,材料力学拉伸曲线出现了波特文-勒夏特利(Portevine Le Chatelier,PLC)效应.当脉冲电流峰值超过96 kA(对应的放电电压超过10 kV)时,试样的延伸率增大508.09％以上.微观表征发现,10 kV电压下材料中位错密度减小,η'相回溶到铝基体并形成过饱和固溶体,从而显著提高了材料塑性.结果表明,瞬时脉冲电流能够实现7075铝合金超快(＜1 ms)固溶.对固溶后7075铝合金采用人工时效处理,材料硬度在人工时效21 h达到峰值,峰值时效处理后材料的硬度达到常规固溶淬火的98.69％.
Abstract
The ultrafast solution with pulsed instantaneous currents and subsequent aging strengthening of aluminum alloys were proposed and the mechanics properties and microstructure evo-lution of aluminum alloys were analyzed by means of macro and micro experiments.The results show that the yield strength of 7075 aluminum alloys decreases gradually with the increase of discharge voltages,but the elongation of 7075 aluminum alloys shows a trend of"small increase-decrease-large increase".When the peak pulse currents exceed 86 kA(corresponding to a discharge voltage of more than 9 kV),the mechanics tensile curve of the material appears the Portevine Le Chatelier(PLC)effects.When the peak pulse currents exceed 96 kA(corresponding discharge voltage exceeds 10 kV),the elongation of the samples increases by more than 508.09％.It is found that the dislocation density in the materials decreases at 10 kV voltage,η'phase dissolves back into the aluminum matrix and forms susaturated solid solution,which significantly improves the plasticity of the materials.The re-sults show that ultrafast(＜1 ms)solution of 7075 aluminum alloys may be achieved by pulsed instan-taneous currents.The strength of 7075 aluminum alloys reaches the peak after 21 hrs of artificial ag-ing,and the hardness after peak aging reaches 98.69％of that of conventional solution quenching.
维普
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