新型Cu-Fe-(C)复相合金的变形及时效析出行为对比研究

Deformation and Precipitation Behavior of Advanced Cu-Fe-(C) Alloys

采用真空感应熔炼和快速凝固法制备了组织性能优异的新型Cu-Fe-(C)复相合金材料,并通过OM、TEM以及力学性能测试分别对熔铸态、超低温深冷轧态、时效态组织和变形行为进行了研究。结果表明,添加溶质元素C有利于避免Cu-3%Fe(质量分数)合金铸态晶界偏析,降低晶内γ-Fe相尺寸,增加其在基体内的数量密度,使得该合金屈服强度较低,而延伸率却较高;超低温深冷轧变形可使Cu-Fe-(C)合金基体内γ-Fe相发生γ-Fe→α-Fe马氏体转变,屈服强度提升至520MPa以上,但是C元素的引入,会使合金残留部分细小γ-Fe相而维持高塑性;进一步经不同温度时效1 h时,2种合金均随温度升高逐渐发生回复再结晶导致硬度降低,不过Cu-Fe-C合金经400℃/1 h处理后发生再结晶的同时,还会析出更多更细小的α-Fe沉淀相,并残留较多位错,最终导致其具有较高的强度和延伸率。此外,对不同状态的沉淀相分布进行了统计和理论强度计算,深入分析了合金强度差异的本质原因。

The advanced Cu-Fe-(C) alloys with dual-phase structure was prepared by combining a vacuum melting and rapid solidification.The microstructure evolution and deformation behaviors of Cu-Fe-(C) alloys under different conditions were studied by OM, TEM and mechanical properties test. The results show that the addition of C element is beneficial to avoid the grain boundary segregation of the Cu-3wt%Fe alloy in the as-cast state, reduces the size of the fine γ-Fe phases and increases the number density in the matrix, so that the alloy has a lower yield strength and higher elongation;although most of the γ-Fe phases can be transformed into α-Fe phases after cold rolling at low temperature, resulting in the significant increased yield strength above 520 MPa, yet, the addition of C can reduce the transformation rate of γ-Fe→α-Fe in the alloy during the cold rolling, causing the higher elongation in this state;additionally, if the cold rolled alloys are aged for 1 h at different temperatures, the hardness of the alloys decreases with the increase of the temperature,corresponding to the recovery and recrystallization;however, compared with alloy 1#, much more fine precipitates and remained dislocations can be found in the alloy 2# after aging at 400 ℃ for 1 h, finally resulting in the higher strengths and elongation. In addition,based on the TEM characterization on the precipitates in the alloys and the calculated strengthening contribution of them, the different strengthening mechanisms were discussed in this paper.