Effects of Homogenization on Structure and Properties of 6061 Aluminum Alloy Billet for Forged Wheel Hub
The homogenized microstructure and subsequent forging process of oil and gas slip 6061 aluminum alloy bar with ϕ254 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 Al2Cu 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 of β-AlFeSi and MgSi phase is reduced from 1.08％,1.11％to 0.73％,0.67％,respectively.Meanwhile,the aggregation amounts of β-AlFeSi and MgSi phase in the segregation layer are significantly reduced,where the maximum size of β-AlFeSi phase is reduced from 60.2 μm to 29.9 μm,and the area fraction is reduced from 1.57％to 0.89％,reducing the stress concentration in the area around the coarse and brittle β-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.
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