The Research Of Fluidity And Hot Tearing For Cast NZ30K Mg Alloy

Mg-3Nd-0.2Zn-0.4Zr (NZ30K) alloy is a new magnesium alloy developed by Shanghai Jiao Tong University. It possesses well mechanical property and corrosion resistance, and has been applied to casting production in small range. However, the fluidity and hot tearing of NZ30K alloy has not been studied systemically at present. Therefore, in this paper, experiments are performed to study the pouring temperature (superheat: 60, 90, 120, 150℃) and mold temperature (the temperature difference between solidus line and mold temperature-TDSM: 100, 200, 300, 400℃) on fluidity and hot tearing susceptibility. Meanwhile, Anycasting4.0 simulation software is used to predict temperature field and stress field.Research confirms that within pouring temperature range from 700℃to 790℃and mold temperature range from 150℃to 450℃, the fluidity of NZ30K alloy is improved by 1.2 times, to 85.3cm, for AZ91D alloy, within pouring temperature range from 658℃to 748℃and mold temperature range from 68℃to 368℃, the fluidity increases by 1.8 times, to 108.4cm. The fluidity of two alloys is almost same at low superheat. Then with the increasing of superheat, AZ91D possesses better fluidity than NZ30K alloy, and the maximum increment is 23.1cm.It is found that the influence of mold temperature is obvious than that of pouring temperature. Hot tearing resistance could be strongly improved by raising mold temperature. When mold temperature is over 350℃(NZ30K), there are no hot tears. The influence of pouring temperature is obvious at low mold temperature (TDSM=400℃). At this temperature, hot tearing susceptibility decrease first and then increase. The better superheat temperature range is 90-120℃. In general, NZ30K has better hot tearing resistance when TDSM is same.From present study, in order to achieve better fluidity and hot tearing resistantance for permanent mold casting, the range of pouring and mold temperature were suggested to be 688-718°C and over 368°C for AZ91D alloy, 730-760°C and over 350°C for NZ30K alloy, respectively.Comparing the experimental results and simulation results through Anycasting4.0, it is found that stress field could qualitatively reflect the influence of mold temperature on hot tearing susceptibility.