Zone Melting And Directional Solidification Of AZ91D Organization And Relative Distribution Of

This subject adopted the standard of AZ91D magnesium alloy ingot to process casting experiments, which used the bridgeman directional solidification system to process directional solidification experiments. The effects of different draw speed and heating temperatures on the microstructures of AZ91D magnesium alloys and the distribution of the second phases(β-Mg17Al12) was investigated in this experiment,the study found that:When the melting temperature of AZ91D magnesium alloy was the same,the organization by the columnar dendrite to the transformation of the columnar crystal in the directional solidification organization of AZ91D magnesium alloy with the speeding up of draw speed,when the draw speed reached100μ m/s,solidified structure for intermittent discontinuity of columnar crystal, central region have similar internal isometric, solidification organization started from columnar crystal to internal isometric transformation;When draw speed was the same,the grain boundary of directional solidification organization was more and more clear with the increase of heating temperature,grain number gradually increased,and grain direction gradually converged.We could obtain more stable uniform columnar crystal structure when the temperature was778℃and draw speed was50μm/s.Directional solidification organization was compared under different zone melting times in experimental process of AZ91D magnesium alloy,and found that the second phase(P-Mg17A112) of AZ91D magnesium alloy had a marked change in the vertical distribution with the increase of number of zone melting,the bottom of sample was almost no second phase, and the second phase distribution was more the more to the top of sample through the three zone melting.In addition, the second phase in the form of spherical most diffused distribution in columnar crystal grain boundary and a small amount of dispersion inside the distribution of grain size in the directional solidification organization of AZ91D magnesium alloy,this were obviously different with ordinary solidification mesh distribution of the second phase.