均匀化对锻造车轮用6061铝合金铸棒组织和性能的影响

Effects of Homogenization on Structure and Properties of 6061 Aluminum Alloy Billet for Forged Wheel Hub

采用光学显微镜、扫描电镜、能谱分析和力学性能测试等手段,对油气滑半连续铸造φ254 mm 6061铝合金圆棒的均匀化态微观组织和后续锻造轮毂过程进行研究。结果表明,铸锭偏析层中含Fe相的数量、大小和形貌,与锻造成形、裂纹形成扩展和轮毂力学性能有着直接的关系。当Fe含量由0.32%降低到0.22%,均匀化温度由550℃提高到约570℃,保温13 h时,铸锭R/2处均匀化态组织中Al_(2)Cu相完全回溶、MgSi相少量残留、AlFeSi相更断续弥散,β-AlFeSi相的面积分数由1.08%减少到0.73%,MgSi相的面积分数由1.11%减少到0.67%;同时,偏析层区域的均匀化组织中β-AlFeSi相和MgSi相的富集量明显减少,β-AlFeSi相的最大尺寸由60.2μm减小到29.9μm,面积分数由1.57%减少到0.89%,减少变形过程中粗大脆硬β-AlFeSi相周围区域的应力集中。此时,锻造轮毂成形性最好,有效的抑制了锻造裂纹的产生,轮毂本体的抗拉强度由322 MPa提高到378 MPa,伸长率由10.2%提高到12.2%。

The homogenized microstructure and subsequent forging process of oil and gas slip 6061 aluminum alloy bar withϕ254 mm by semi-continuous casting were investigated by OM,SEM,EDS and mechanical property test tech⁃niques.The results indicate that the quantity,size,and morphology of Fe-rich phase in the segregation layer of the ingot are directly related to forging forming,crack formation and propagation,and mechanical properties of the wheel hub.With Fe content decreasing from 0.32%to 0.22%and homogenization temperature rising from 550℃to 570℃,and holding time of 13 h,the Al_(2)Cu phase at R/2 of the ingot is completely dissolved,a small amount of MgSi phase remains,and the AlFeSi phase is intermittently dispersed,where the area fraction ofβ-AlFeSi and MgSi phase is reduced from 1.08%,1.11%to 0.73%,0.67%,respectively.Meanwhile,the aggregation amounts ofβ-AlFeSi and MgSi phase in the segregation layer are significantly reduced,where the maximum size ofβ-AlFeSi phase is reduced from 60.2μm to 29.9μm,and the area fraction is reduced from 1.57%to 0.89%,reducing the stress concentration in the area around the coarse and brittleβ-AlFeSi phase during deformation.At this point,the forged wheel hub exhibits desirable formability,which effectively suppresses the generation of forging cracks.The tensile strength and elongation of the wheel hub are increased from 322 MPa,10.2%to 378 MPa,12.2%,respectively.