Cu-2.1Fe合金中共格γ-Fe粒子的粗化规律与强化效果

STUDY OF THE COARSENING AND HARDENING BEHAVIORS OF COHERENT γ-Fe PARTICLES IN Cu-2.1Fe ALLOY

采用TEM,SEM,硬度及电导率测试等手段,研究了Cu-2.1Fe合金在不同温度长期时效后析出相形貌和合金性能的变化.结果表明,500℃为合金最佳时效温度,峰时效硬度平台期较长.合金峰时效时γ-Fe粒子平均直径约12 nm,且与基体完全共格.g-Fe粒子长大后会渐渐失去共格效应且方形化,粗化规律符合Lifshitz-Slyozov-Wagner(LSW)规律,粗化激活能为222 kJ/mol.Fe粒子的时效强化效果不显著,最大强度增量约100 MPa.Cu-2.1Fe合金欠时效时遵循的强化机制为共格强化机制,合金过时效后强化机制为Orowan强化机制,理论预测与实验结果符合良好.

As one of the most widely used integrated circuit（IC） lead frame materials,Cu-2.1Fe alloy（C19400） shows excellent comprehensive properties,such as 90° bend fatigue,90° bend formability,corrosionproof,solder ability and resistance of solder peeling off.As a successful medium-strength and high-conductivity copper alloy,the Cu-2.1Fe alloy is strengthened by precipitation hardening and work hardening.Metastable coherent γ-Fe particles will precipitate from supersaturated copper matrix during aging.The effects of long-term aging at different temperatures on the γ-Fe coarsening characteristics and the mechanical properties of Cu-2.1Fe alloy were investigated,by means of conventional TEM,SEM,hardness,tensile strength and electrical conductivity testing.The results show that solution-treated Cu-2.1Fe alloys can reach its peak hardness and maintain for a longer time when aging at 500 ℃.The maximum of strength occurred at a particle size of about 12 nm in mean diameter.The coarsening kinetics of γ-Fe follows Lifshitz-Slyozov-Wagner（LSW） theory and the activation energy for growth is estimated to 222 kJ/mol.Furthermore,it is found that coherent Fe particles gradually evolve into semi-coherent and cubical particles after aging for a long time and at high temperatures.The aging strengthening effect of Fe particles is not significant,and the maximum increment of stress is about 100 MPa.The strengthening mechanism of undeformed Cu-Fe alloy is coherency strengthening during the under-aged stage and changes to Orowan mechanism during the over-aged stage.Experimental results are in agreement with theoretical predictions.