Low-cycle Fatigue Behavior Of Die-cast AS41 And AE42 Magnesium Alloys

At present, lightweight products are the pursuit of modern technology. Magnesium alloys are becoming more and more valued, because of its low density, high specific strength and specific stiffness characteristics. According to statistics,90% commercial magnesium alloys are used under die casting process. As engineering material, fatigue fracture is one of the most important failure modes of magnesium alloys. Based on that, research on low cycle fatigue behavior of die-cast magnesium alloys have a certain practical value.In this paper, Through micro structural observation XRD comparative analysis results of AS41 and AE42 die casting magnesium alloys show:AS41 magnesium alloys texture become grain refinement after solid solution, At the same time,β-Mg17Al12 Phase dissolve inα-Mg body and Mg2Si Phase becoming globalization. Because of solution and aging about the AE42 alloys, microstructure distribute more uniform and AI11RE3 and Al3RE Phase dissolve inα-Mg body more dispersion than die casting states.At room temperature, with different heat treatment states, AS41 and AE42 magnesium alloys, which can exhibit the cyclic strain hardening levels with different processing states, under the same total strain amplitudes, can show more higher low-cycle fatigue life. The cyclic strain hardening levels is related to strain amplitudes and Processing states. To AS41 magnesium alloys, under the same strain amplitude, the cyclic strain hardening levels is not significant between the die casting and solid solution state; To AE42 magnesium alloys, under the lower strain amplitude, the cyclic strain hardening at T6 is higher than die casting, under the higher strain amplitude die casting states is higher. while comparison of AS41 and AE42 magnesium alloys, under the higher total strain amplitude, AE42 alloys show the higher fatigue life than AS41 magnesium alloys, but AS41 higher under the low total strain amplitude.Under the same total strain amplitude, The low-cycle stress fatigue of two alloys increase in accordance with the AE42(F),AS41(E),AS41(T4),AE42(T6) whileΔεt/2≤0.4%; otherwise will increase in accordance with AS41(F),AE42(F),AS41(T4),AE42(T6) whileΔεt/2≤0.5%. For AS41 and AE42 magnesium alloys,with different processing states, the relations between the plastic strain amplitude and elastic strain amplitude,and reversals to failure can be described by the Basquin and Coffin-Manson equations respectively. Using the SEM analysis on the the fatigue specimens shows that the surface of defects near at the casting can initiate the fatigue cracks, and the propagate in a transgranular mode.