以冷却速率101～103K/s的不同凝固条件制备了Cu-10Ag合金及其原位纤维复合材料.研究了铸态和形变态合金的结构与性能.铸态合金的结构由Cu相、Ag沉淀相和(Cu+Ag)共晶组成.通过大变形发展为Cu-Ag合金原位纳米纤维复合材料,其中由Ag沉淀相所形成的Ag纤维尺寸(d)与真实应变(η)呈指数函数关系:d=C·exp(-0.228η),(Cu+Ag)共晶中Ag层转变为更细的纳米Ag纤维.Cu-Ag合金原位纳米纤维复合材料显示了两阶段应变强化效应:在低真实应变阶段主要表现为加工硬化或位错强化,在高真实应变阶段主要表现为超细Ag纤维强化或界面强化.快速凝固的Cu-Ag合金原位纳米纤维复合材料比慢速凝固材料具有更高的包括极限拉伸强度和电导率在内的综合性能.在形变过程中复合材料的强度与电导率的演变出于相同的结构原因.
The Cu-10wt%Ag alloy was prepared under two different solidification conditions with cooling rates of 101～103K/s. The influences of the solidification rate on the microstructure, the strength and the electrical resistivity of the Cu-Ag alloy in situ filamentary composites were studied.It was found that the size of Ag filaments formed by Ag precipitates in the cold deformed composites grain size and therefore was under the influence of solidification rate. The rapid solidification refined the original dendrites of the cast alloys, reduced the spacing between the dendrites, increased the proportion of (Cu) + (Ag) eutectic and at last refined the Ag filaments of the composites. The alloys solidified in different cooling rates showed a two-stage strain strengthening effect. It was suggested that the main strengthening mechanisms for the in situ filamentary composites are the work hardening at the low strain stage as η＜ηp and the ultra-fine Ag filaments or interfaces strengthening at the high strain stage as η＞ηp, here ηp is the turning point in the true stain dependence of UTS.The alloy solidified rapidly possessed lower UTS at the first stage and higher UTS at second stage than that solidified slowly. The similar tendency was observed for the true strain dependence of electrical resistivity.
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