Study of microstructure and mechanical properties of aluminum 7075 alloy extruded in a semi-solid state

In this paper, the effect of strain-induced melt activation process parameters and the effect of forward extrusion parameters on the semi-solid state in the microstructures and the mechanical properties of aluminum 7075 alloy are investigated. The isothermal holding time, isothermal temperature, and predeformation ratio-which are parameters of strain-induced melt activation method-have been selected at 5-20 min, 590-620 degrees C and 10%-40% respectively. Also, the extrusion ratio is 68%-89% and the extrusion speed is 0.05-0.5 m/s; the parameters are driven from forward extrusion. Samples at an extrusion ratio of 68%, 75%, and 82% were extruded defectively. Sound products were obtained at an extrusion ratio of 89%. So among these stated parameters, it was derived that the extrusion ratio has the greatest effect on obtaining sound products. At predeformation ratios higher than 30%, the shape factor decreased, and the grain size increased, it was clear that a predeformation ratio higher than 30% is inefficient for the process. The yield and ultimate stress for thixo-extruded samples were higher than for hot extruded samples. As expected, most of the mechanical properties in between sound samples (yield stress of 327 MPa, ultimate stress of 459.5 MPa, and elongation 14%) were related to the sample of finest-grained microstructures. The finest-grained sample (25.85 mu m) was achieved at isothermal holding time, isothermal temperature, predeformation ratio, and extrusion rate equal to, 20 min, 590 degrees C, 30%, 0.2 m/s respectively.