Evolution of microstructure and hardness in AZ31 alloy processed by high pressure torsion

Evolution of microstructure in AZ91 alloy processed by high-pressure torsion

“…The material constants are H 0 = 76 MPa and k H = 233 MPa lm 1/2 , which is relatively higher than those found for AZ31 and AZ61 alloys (H 0 = 647-697 MPa and k H = 118-170 MPa lm 1/2 ) [7,22,43]. Thus, the ultrafine-grained AZ91 alloy shows a relatively higher level of hardness than for AZ31 and AZ61 alloys processed by HPT and ECAP processing at room temperature and elevated temperatures [21,22,44]. The difference in k H can be attributed to the difference in alloying constituents in the mentioned alloys, where the high content of alloying element in the AZ91 alloy resulted in a lowering of its stacking fault and thus a finer microstructure and a higher dislocation density in the AZ91 alloy after processing than in the AZ61 and AZ31 alloy [19,21,22].…”

“…The effect of dynamic recovery was absent as the alloy has been processed at room temperature. It is anticipated that the homogeneity developed gradually with further straining at room temperature as mentioned by several investigators [20][21][22][23]. The grain refinement in the processed alloy at 423 K has developed efficiently by twinning intersections and the grain subdivision mechanism.…”

“…This consistency in the AZ91 alloy has not been observed in the AZ31 alloy or AZ91 alloy processed by ECAP [26] and FSP [27]. This is attributed to the difference in the aluminium content and stacking fault energy in both alloys, which control the extent of grain refinement, dislocation density, achieved homogeneity and resultant mechanical properties [14,21,38]. The behaviour of strain hardening and homogeneity of microhardness in the AZ91 alloy follows a standard model of hardness evolution with increasing equivalent strain reported in earlier work [20].…”

“…The AZ91 alloy with a low stacking fault energy [38] shows a slow rate of dynamic recovery during processing at room temperature, thus strain hardening occurs at a fast rate during processing [20,32]. The AZ91 alloy processed in HPT showed an earlier saturation in the microhardness distribution than for the AZ31 alloy [21] processed in HPT at room temperature. The stacking fault energy is lower, and the fraction of particles of b-phase is higher in the AZ91 alloy than for the AZ31 alloy [38,39].…”

Microstructural Evolution and Properties of a Hot Extruded and HPT‐Processed Resorbable Magnesium WE43 Alloy

“…This suggests there will be an inhomogeneity across the disk but, by contrast, many results show that this inhomogeneity gradually disappears with increasing deformation. For example, there is a gradual evolution towards microhardness homogeneity in numerous metallic alloys such as Al-4wt.%Mg, [31] AZ31, [32] Al-6063 and Cu-0.1% Zr. [33,34] A detailed review is now available summarizing these trends for a large number of metals.…”