The features of plastic deformation of magnesium alloy AZ31 by tension in the temperature range 4,2-295 K are examined depending on its microstructure after squeeze casting (SC) and severe plastic deformation (SPD) via hot rolling and equal channel angular pressing. The SPD processing results in decrease of grain size and formation of a texture favorable for basal dislocations glide. It is found that in the temperature range 4.2-25 K the plastic deformation becomes unstable (serrated) with stress jumps in the SPD alloy greater than in the SC one. The temperature dependence of yield stress of the alloy is typical of thermally activated unpinning of dislocations from short range obstacles. The ratio of yield stresses for SPD and SC samples at given temperature is explained by hardening due to refinement of grain size and softening owing to favorable texture. The work hardening rate of alloy decreases a with grain size, but the ductility (strain to rupture) increases due to texture. The strain rate sensitivity of flow stress at T ≤ 100 K does not depend on alloy microstructure and is determined by intersections with forest dislocations. As the deformation temperature increases in the range 150-295 K, the strain rate sensitivity rises owing to activation of dynamic recovery and contributions of diffusion processes under plastic deformation of fine-grained materials. PACS: 62.20.-x Mechanical properties of solids; 62.20.F-Deformation and plasticity;.
|Number of pages||9|
|Journal||Fizika Nizkikh Temperatur (Kharkov)|
|Publication status||Published - Dec 2010|
- Equal channel angular pressing
- Low temperature
- Magnesium alloy
- Plastic deformation