Abstract
An AZ91 alloy pretreated by ultrasonic vibration (UV) was subjected to extrusion to refine the microstructure. The results indicated that the UV pretreatment had a strong influence on the microstructure evolution and mechanical properties of the extruded AZ91 alloy. With UV pretreatment, a fine and uniform microstructure with an average grain size of 13.5 μm was obtained, and the fraction of the fiber-like, partially-recrystallized, structure was markedly reduced. In addition to the superior mechanical properties such as a yield strength of 256 MPa, an ultimate tensile strength of 320 MPa and a fracture elongation of 9.7% were achieved in the extruded AZ91 alloy with UV pretreatment.
