Influences of Extrusion Temperature on Microstructure and Properties of AZ91D Alloy

In order to improve integrated mechanical properties of AZ91D alloy,its hot extrusion deformation was done.The five temperature(300,330,360,390 and 420 ℃) and extrusion ratio of 45 were adopted.The forward extrusion was done on prompt forming oil-pressed machine of 6400 kN.The tensile test and metallographic structure observation of the samples were done after extruding.The results show that dynamic recrystallization occurs during hot extrusion deformation,and makes grains fine and microstructure homogeneous,therefore hot extrusion can improve mechanical properties of the alloy effectively.Meanwhile,with the increase of temperature,the tensile strength and yield strength improve.But when beyond 390℃,recrystallization continues to the end,while grains grow up too,so yield strength keeps going up,while tensile strength reduces.When temperature is 390℃,tensile strength reaches 390 MPa,yield strength goes up to 288 MPa and the elongation rate is 11%.It is the optimum extrusion program.