Study On Ignition Proof Magnesium Alloys And Its Ignition Proof Principles Under Nitrogen Atmosphere

Spray forming technology is an effective way to prepare high-performance large-size rapidily solidified magnesium alloys.It has high cost performance advantage to use nitrogen as the atomization gas of spray forming magnesium alloy technology,however,magnesium react with nitrogen easily.The problem of using nitrogen as the atomization gas of spray forming magnesium alloy technology is how to assure the safety of spray forming.In order to prepare high-performance magnesium alloys safely by spray forming,alloying was used to prevent magnesium alloys from nitriding,the ignition proof properties of magnesium alloys were studied, and spray forming process parameters were optimized.In the present dissertation,ignition proof alloying elements were selected by thermodynamic calculation.The ignition proof properties of block magnesium with addition of Y,Ce,Nd and Ca under nitrogen atmosphere were studied by homemade device.The ignition proof properties of magnesium alloy powders and the nitridation dynamics curves were studied by thermogravimetric instrument.X-ray diffraction, scanning electron microscopy and energy spectrum were employed to study the surface nitriding film of Mg-Ca alloys.The results show that the addition of Y,Ce, Nd and Ca can significantly improve the ignition of magnesium alloys under nitrogen atmosphere,and Ca is the most effective element for heightening ignition-point.The nitridation dynamics curves of Mg-1Ca,Mg-5Ca and Mg-5Y measured at 500℃and 600℃follow the parabolic-line law.The nitriding film of Mg-Ca alloys composed of Ca₃N₂,Mg₃N₂ and CaMg₂N₂.Nitriding film is very dense and accumulated closely by a large number of irregular particles.Mg-7Al-1.5Zn-4.5Ca-1Nd alloy was prepared safely by spray forming technology with using nitrogen as atomization gas.Grain of the alloy is fine,and uniform distribution.Its tensile-strength is 450MPa and specific elongation is 7%.