挤压温度对7085铝合金挤压棒组织和性能的影响

Influence of Extrusion Temperature on Microstructure and Properties of 7085 Aluminum Alloy Extrusion Rod

采用室温拉伸、金相显微镜(OM)、扫描电镜(SEM)等分析方法,研究了挤压温度对7085铝合金挤压棒组织和性能的影响。结果表明,经热处理后的挤压棒纵向、横向拉伸性能随挤压温度的变化而显著变化。随挤压温度升高,挤压棒纵向的屈服及抗拉强度均显著降低,而伸长率变化不大;横向的屈服强度显著降低,抗拉强度变化不大,伸长率显著提高;纵向、横向的拉伸性能差异随挤压温度的升高而迅速降低。通过高倍组织观察发现,当挤压温度为380℃时,经热处理后呈现出典型的条带状变形组织形貌,温度提高到420℃时,挤压过程中发生了显著的动态再结晶,形成了细小的等轴颗粒。晶粒形貌的差异,直接影响到力学性能及断裂机理。动态再结晶的形成,消除了挤压时形成的挤压效应,降低了挤压棒纵向的强度,同时,使合金横向断口由沿晶断裂为主转变为典型的穿晶滑移断裂为主的特征,有效改善了合金的塑性。

The influence of extrusion temperature on the microstructure and properties of 7085 extruded rods was investigated by tensile test at room temperature,optical microscopy(OM)and scanning electron microscopy(SEM).The results indicate that the longitudinal and transverse tensile properties of extruded rods after heat treatment are varied significantly with extrusion temperature.With the increase of extrusion temperature,the longitudinal yield and tensile strength of the alloy are decreased significantly,while it can be neyletted in elongation.The transverse yield strength is decreased significantly with the little in tensile strength,while the elongation is increased greatly.The difference between longitudinal and transverse tensile properties is decreased rapidly with the increase of extrusion temperature.The macrostructure observation presents typical banded deformation morphology when the extrusion temperature is 380℃.When the temperature is increased to 420℃,significant dynamic recrystallization occurs during the extrusion process,leading to the formation of fine equiaxed particles.The difference of grain morphology directly affects the tensile properties and fracture mechanism.The‘extrusion effect’formed during extrusion is eliminated by dynamic recrystallization,reducing the longitudinal strength of the extrusion rod.Meanwhile,the dominated characterization of transverse fracture is converted from intergranular fracture to typical transgranular slip,effectively improving the plasticity of the alloy.