The Effect Of Cooling Rate On Magnesium Alloy's Microstructure And Properties

AZ31 and AZ91 magnesium alloys have been studied in this paper. Different cooling rates were obtained by a cooling block set in the sand mould. Mixture gas including F6S and N2 was used as the protective atmosphere in the experiment. Cooling carve was recorded by AX110. In the side of cooling block the cooling rate was 4.95 4.95k/s maximally, while in the other side it was only 0.4k/s. It has been found that the dendrite arm spacing changed as the cooling rate changed. We can obtain the relationship between dendrite arm spacing and cooling rte by analyzing the result. For example, the relationship about AZ31 alloy was y=75.365x-0.3333, while the relationship about AZ91 alloy was y=62.861x-0.3363.At the same time, the relationship between dendrite arm spacing and mechanical properties was obtained as follows:AZ31 alloy :UTS=0.0006X2-0.3288X+232.77 YS=0.0107 X2-1.9247X+189.96â–½=6E-06X2-0.0019X+0.1851 HV=0.0213X2-3.496X+393.25AZ91 alloy:UTS=0.01X2-2.1698X+297 YS=0.0106 X2-1.9901X+199.9â–½=6E-05X2+0.0086X-0.2322It is also found the fluid mechanism from the results of the experiment. It's proved that the fluid process involved two stages. The solidification process is explained by fluid mechanism, and the different mechanical properties of them are also studied.