The Effect Of ECAP Deformation On Mechanical Property And Damping Capacity Of AZ31 Magnesium Alloy

Equal channel angular pressing (ECAP) was performed on the extruded AZ31 magnesium alloy at the temperature from 200℃to 300℃for different passes. The microstructure of the as-extruded magnesium alloy and ECAPed ultra-fine grained magnesium alloy were examined by means of optical microscopy (OM), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). Tensile deformation behavior of the as-extruded magnesium alloy and ECAPed ultra-fine grained magnesium alloy at ambient temperature were investigated. The basal plane texture was measured qualitatively by the X-ray diffractometer. The damping capacities were measured by dynamic mechanical analyzer (DMA) Q-800 type.The results showed that when ECAP was performed on AZ31 magnesium alloy at 200℃and 250℃, The grains were significantly refined because of recrystallization, The average size of grains was 2μm. When ECAP was performed at 300℃, The grains become equiaxed grains, the average size of grains was 8μm. After uniform heat treatment, few precipitated phase Al17Mg12 was seen. With increasing of ECAP passes, the yield stress of the alloy ECAP-ed at 200℃and 250℃was increased, and then decreased because of fined grains and difference of texture; the yield stress of the alloy ECAPed at 200℃and 250℃was increased, while the elongation to failure at ambient temperature was effectively improved because of fined and homogeneous textured.The investigation of the strain amplitude dependent damping capacity indicated that the curve showed strain amplitude dependent and independent regions. The curves were well interpreted by G-L dislocation model. The main factor of deciding the strain amplitude dependent damping capacity was length of mobile dislocation line and its sliding distance, but for AZ31 magnesium alloy, it was density of mobile dislocation. Capacity of strain amplitude independent of deformed AZ31 was effectively improved by removing suboundary structure and controlling density of dislocation which can keep a better ambient damping capacity, and also remain good mechanical property at the same time.The investigation of the temperature dependent damping capacity showed that the damping capacity increased when the temperature increased or the frequency decreased. The curves of the temperature dependent damping capacity of the as-extruded magnesium alloy and ECAPed AZ31 magnesium alloy exhibit two typical peaks, with increasing of temperature. Two peaks were found between 150℃and 200℃, fore and after 250℃. The first peak was induced by the viscosity-slipping of grain boundary. The second peak was induced by recrystallization. The ECAP-ed AZ31 at 200℃exhibit better the temperature dependent damping capacity than The ECAP-ed AZ31 at 300℃...