退火温度对冷静液挤压铜包铝线材组织和力学性能的影响

EFFECTS OF ANNEALING TEMPERATURE ON THE MICROSTRUCTURES AND PROPERTIES OF COPPER CLADDING ALUMINUM WIRE PREPARED BY COLD HYDROSTATIC EXTRUSION

研究了退火温度对冷静液挤压铜包铝线材组织和性能的影响规律,在界面断裂形式分析的基础上探讨了其作用机理,结果表明:直径为6 mm的冷静液挤压态铜包铝线材合理的退火温度为350℃,低于200℃退火时,纯Cu包覆层只发生回复,复合线材的力学性能得以部分恢复;350℃退火时,铜层再结晶基本完成;复合线材的抗拉强度降到最低,延伸率则达到最高;400℃退火时,铜层晶粒开始长大,复合线材的延伸率开始劣化,界面结合强度随温度的变化呈先增加后降低的趋势,而界面的断裂则由低温退火时的铝基体塑性断裂转变为高温退火后Cu/Al界面的脆性断裂。

The effects of annealing temperature on the microstructure and mechanical property of copper cladding aluminum wires fabricated by cold hydrostatic extrusion were investigated, and its influence mechanism was discussed on the basis of different interface fracture modes. The experimental results showed that the appropriate annealing temperature is 350 ℃ for as-extruded wires with 6 mm in diameter. As the annealing temperature is below 200 ℃, a recovery process appeared in copper sheath and the mechanical properties of the cladding partly recovered. The recrystallization of copper proceeded sufficiently at 350℃, the tensile strength and elongation of the cladding wire reached minimum and maximum, respectively. The growth of copper grains occurred during annealing at 400 ℃, which decreased obviously the elongation of the wire. With the increase in annealing tem- perature, the interface strength of the Cu/Al bimetal wire increased to a maximum value and then decreased, the interface fracture location transformed from Al side to the Cu/Al interface and the fracture mode transformed from ductile to brittle.