Research On The Properties Of Warm Deformation Of Magnesium Alloy AZ91D

The research on the plastic deformation of magnesium alloys is one of the hot spots on the material field. As their structure, magnesium alloys have the smaller plastic deformation at the normal atmospheric temperature, and their many forming technologies should be proceeded at the higher temperature. It is very important for the forming technologies to research on warm deforming behavior of the magnesium alloys.This article takes the magnesium alloy AZ91D most widely used in industry as the research object, through the thermal simulation compressing experiment, the normal pulling experiment, and the analysis of microstruture, synthetically discusses the deforming behavior and microstruture changing rule of magnesium alloy AZ91D at the as-cast and homogenizing annealing states, the following findings are obtained:Through the thermal simulation compressing experiment, a study is carried out that is on hot deforming behavior and microstruture changing rule of magnesium alloy AZ91D at the as-cast and homogenizing annealing states. After the analysis of the hardness is done to the compressed samples. The result indicates that the hot deformations of the two states have the character of dynamic recrystallization;the stress-strain curves of the different state in the same deforming condition are analyzed and found that the homogenizing annealing process can improve the capability of figuration at the low temperature and low strain rate ( below 200℃, 0.001s-1～0.01s-1 ), but it has little effect on the capability of figuration when the deformation temperature is over 300℃;the three-dimensional plots of the sample's rupture degree-strain rate-deformation temperature of magnesium alloy AZ91D at the different state are drawed and the relations between the triple are Perceived visually;the hardness of the compressed samples is the best at 300℃and 0.001s-1 and 0.1s-1 strain rate. Finally with the experimental results, the reasonable deformation condition of magnesium alloys AZ91D at the different state is ascertained and the models of the deforming resistive stress are established.Moreover, the hot deforming behavior of magnesium alloy AZ91D is compared with magnesium alloy AZ31 and ZK60 at the same deforming condition( 200℃～400℃and 0.01s-1～0.1s-1). The result indicates that the hot deforming behavior of magnesium alloy AZ91D is inferior to magnesium alloy AZ31, however, it is superior to magnesium alloy ZK60.In the pulling experiment, it is found that the plasticity is higher while the strength is lower by comparing with the tensile strength, yield strength and elongation of magnesium alloy AZ91D at the as-cast and homogenizing annealing states. Fractographies of the tensile fractures also demonstrate that though both the tensile fractures at homogenizing annealing and the as-cast state belong to quasi-cleavage fracture, but the number of the ductile dimple at homogenizing annealing state is more larger, and so the plasticity of as-cast AZ91D magnesium alloy at normal temperature is improved and the result is consistent with the mechanics analysis.