Investigation on microstructure and mechanical properties of Al-5.50Zn-2.35Mg-1.36Cu alloy fabricated by hot extrusion process

Hot extrusion experiments were conducted on Al-5.50Zn-2.35Mg-1.36Cu (wt%) alloy under various temperatures and extrusion speeds. Results indicated that dynamic recovery occurred at low temperature and then dynamic recrystallization was triggered at higher temperature or speed. High billet temperature reduced the grain size and increased the volume fraction of Al23CuFe4 and AlMgZn. When the extrusion speed was enhanced to 0.5 mm/s, the peak of MgZn2 phase diminished in the results of X-ray diffraction. The strong brass and S components appeared in all the extruded specimens. Texture intensity gradually decreased with increasing temperature and the fraction of texture components was also significantly affected by the extrusion parameters. The extruded alloy exhibited the highest ultimate tensile strength of 350.2 MPa at 480 degrees C and 0.5 mm/s and the best elongation of 16.78% at 520 degrees C and 0.1 mm/s. Moreover, the extrusion speed had more significant effects on the tensile properties than that of the temperature.