文摘
Al-12Zn-2.4Mg-1.2Cu (wt%) alloy billets as-deposited were extruded to be Φ100 mm bar, Φ100 mm × lΦ 80 mm seamless pipe and 160 mm × l15 mm stripper plate under different deformation ways. The microstructures of the products as-heat-treated were studied by optical metallographic and scanning electron microscope, and the mechanical properties were also measured. Metallographic microstructures show that the grains in the initial billets are almost equiaxed with diameter about 20 μm. There are some second phases precipitated distributing in the grains and on the grain boundary. The deposited ventages around the grains as-deposited were welded together by a welding metallurgy way during extrusion process. The flow lines were clearly observed in the extrusion direction in all different extruded products. For the products as-heat-treated, the tensile strengths, the yield strengths and the elongations of the bars are 688 MPa, 654 MPa and 12% in the cross direction (CD), while 698 MPa, 674 MPa and 10.5% in the longitude direction (LD); for the plates they are 783 MPa, 748 MPa and 7% in CD; while 751MPa, 719 MPa, and 8% in LD; for the pipes they are 781 MPa, 735 MPa and 9% in LD. Scanning electron microscope examination reveals the fracture characteristics of the fractured specimens exhibit three different fracture models which are ductile fracture, mixed fracture and brittle fracture corresponding to bars, pipes and plates, respectively.
