The Study On The Corrosion Residual Strength Of Heat Treatment AM50Magnesium Alloy

AM50Magnesium alloy is the lightest structural metal, it has the high specificstrength, rigidity, the good damping and noise reduction capability and liquid formingability, so it can be used widely in automobile industry and aviation industry. Thecharacteristics of energy saving and easy recycling make the AM50Magnesium alloyin line with the title of “The green structure material of21st century”. However, thedevelopment and application was very limited because of low intensity and poorcorrosion resistance.This thesis takes AM50Magnesium alloy as the subject, adopting sometechnologies of heat treatment process to heat treatment, such as T4water quenchingheat treatment, T4furnace cooling heat treatment and T6heat treatment. The mainresearch direction is the influence of different technologies of heat treatment on thecorrosion residual strength of AM50Magnesium alloy. We can get the result that eachperformance of AM50Magnesium alloy is the best after dealing with the T6technology processing from the comparative analysis of microstructure, corrosionmacro morphology, polarization curve, corrosion rate and corrosion residual strength.AM50Magnesium alloy is found that it is dissolved in matrix after dealing withthe T4furnace cooling heat treatment, and achieving a good solid solution effect.From the experiments of polarization curve and weight loss test, we can find that itscorrosion resistance can be increased up to220MPa, and the strength is also improvedin the tensile test. However, because the corrosion process is pitting corrosion, thedepth of pitting corrosion affects the residual intensity of T4furnace cooling heattreatment during the process of residual intensity test. After24-hour corrosion, the restintensity is lower than as-cast AM50magnesium alloy. Since changed to another kind of heat treatment–T4water quenching, the β phase of AM50magnesium alloydissolves into the alloy group, because of the heat treatment of water quenching, apart of β phase is separated out in grain boundary. The AM50magnesium alloy of T4water quenching got through the experiment is promoted remarkably incorrosion-resistance and mechanical property. And both of those are higher thanas-cast AM50magnesium alloy and the alloy of T4heat treatment, and the strength ofextension is up to225MPa. The depth of the corrosion pit becomes shallower, but theaverage depth is deeper than the corrosion pit of as-cast AM50magnesium alloy. Sothrough the experiment of rest intensity, we get the result that T4water quenchingheat treatment is higher original titanium alloy.To achieve more ideal enhancement effect, we chose T6heat treatment. Thealloyed β phase processed by T6heat treatment is found that some is dissolved inmatrix and some is separated from crystal boundary. Compared to T4heat treatmentand casting AM50magnesium alloy, its corrosion resistance improves, and its tensilestrength reaches up to240Mpa. From our experiment of corrosion residual intensitywhich last for432hours, we have come to the conclusion that its residual intensityalso exceeds casting magnesium alloy.To sum up, for the AM50magnesium alloy processed by T6heat treatment, itscorrosion intensity, mechanical property as well as the corrosion residual intensity allimprove, which increases its working time in stress corrosion condition and broadensthe application scope of AM50magnesium alloy in practical production.