| Due to the pressure of environmental pollution and energy shortage,the material has put forward higher requirements for energy saving and emission reduction.As a green engineering material,magnesium alloys has been widely concerned in the aerospace and automotive industries.However,the absolute mechanical property index of magnesium alloy can't be achieved the requirement of industrial applications now.The purity of magnesium alloy melt is one of the important factors to affect their properties,and magnesium alloy melt will inevitably be brought into some inclusions(Fe,Ni,et al)from melting tools,equipment and flux which result in the decrease of the properties of magnesium alloys.In particular,the influence of impurity iron is very large,which not only reduces the corrosion resistance of magnesium alloy,but also has a great influence on mechanical properties.At present,there are a lot of purification methods and techniques of research.However,the effect of Steel mould with different components on the impurity content of magnesium alloy at high melting temperature and the mechanism of the interaction between the magnesium alloy melt and the tool die is few studied.Therefore,we need further research,and provide a theoretical basis for the optimization design of mould,and provide the basic data for the multi magnesium alloy phase diagram with impurity calculation.Based on the commercial AZ series magnesium alloy as the research object,and the pandat thermodynamics calculation software is used to establish the multiple magnesium alloy phase diagram of AZ series with Fe,Ni,to study the solubility of Fe and Ni in AZ series magnesium alloy.The calculation results show that the solubility of Fe in AZ series magnesium alloy was increased with the increase of temperature,and the solubility of Fe in AZ31 was the largest.With the addition of Mn,the solubility of Fe in AZ series magnesium alloy was decreased.The solubility of Ni in AZ series magnesium alloy was increased with the increase of temperature,and the solubility of Ni in AZ31 was the largest.The solubility of Ni in AZ system magnesium alloy is two orders of magnitude higher than that of Fe in AZ system magnesium alloy,and with the addition of Mn,the solubility of Ni in AZ system magnesium alloy was not changed.The enthalpy of formation of binary intermetallic compounds in Mg,Al,Zn,Mn,Fe was rationalized using the Miedema model at the solid state diffusion,Al-Fe,Al-Mn has the lowest enthalpy of formation in all binary intermetallic compounds.Similarly,the enthalpy of formation of binary intermetallic compounds in Mg,Al,Zn,Mn,Ni was rationalized using the Miedema model at the solid state diffusion,Al-Ni,Al-Mn has the lowest enthalpy of formation in all binary intermetallic compounds.The Gibbs free energy of binary intermetallic compounds in the(AZ31-Fe?AZ61-Fe?AZ80-Fe?AZ91-Fe magnesium alloy without Mn),(AZ31-Fe?AZ61-Fe?AZ80-Fe?AZ91-Fe magnesium alloy with Mn)were calculated using the Pandat thermodynamics calculation software,respectively.The results show that FeAl,Fe-Al-Mn have the lowest Gibbs free energy at melting temperature,respectively.The Gibbs free energy of binary intermetallic compounds in the AZ31-Ni?AZ61-Ni?AZ80-Ni?AZ91-Ni magnesium alloy with or without Mn were calculated.The results show that Al3Ni2 and AlNi have the lowest Gibbs free energy at melting temperature.On the basis of the above theoretical calculation and analysis,experimental verification object is selected to study the interaction between it and carbon steel in the smelting process,which showed that the experimental results are in consistent with the calculated results.The effect of carbon steel on the Fe content in the melt of AZ31 B magnesium alloy was investigated by inductively coupled plasma-atomic emission spectroscopy(ICP)at different melt temperatures and different melting holding time.The microstructure and element distribution of diffusion reaction layers were analyzed by scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The results showed that no obvious interaction was observed between AZ31 B magnesium melts and carbon steel below 720?,and the content of Fe in the magnesium alloy melt was not increased.At 720?,the Fe began to be dissolved to magnesium alloy melt from carbon steel,and at the same time Al and Mn in the magnesium alloy melt diffused to carbon steel,the Fe-Al-Mn diffusion reaction layer was formed on the surface of carbon steel.Above 720?,more Fe atoms from carbon steel were dissolved to the magnesium alloy melt and more Al and Mn atoms diffused to carbon steel,and Fe-Al-Mn layer,Fe3 Al layer and carbon steel layer with trace Al were found in carbon steel.When the melt temperature increased to 760-780?,the iron content in the melt was found to increase to above 100 ppm. |
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