Quenched and Annealed Microstructures of Hot Worked Magnesium AZ31

Abstract

The microstructures of magnesium AZ31 are examined following hot compression testing and annealing. The grain size, fraction dynamically recrystallized and, in a couple of cases, the crystallographic texture are reported. The progress of dynamic recrystallization and the recrystallized grain size were sensitive to processing conditions, as expected. This effect was more marked in the former than in the latter, compared to other metals. It was also found that, for structures containing between 80 and 95% dynamic recrystallization, abnormal grain growth occurred during annealing. Irrespective of the whether or not abnormal grain growth occurred, the annealing step weakened the crystallographic texture.

Microstructural Development during Hot Working of Mg-3Al-1Zn

“…Several studies have examined the dynamically recrystallized grain size developed during the hot deformation of magnesium and developed equations that relate it to the deformation conditions (either stress or Z). [5][6][7]12,[27][28][29][30][31] While some researchers have shown that the relationship between the dynamically recrystallized grain size and the deformation conditions can be described using a power law (e.g., References 27 and 29 through 31), others have found that this relationship was not linear and attributed this to a change in the rate controlling dynamically recrystallized mechanism, i.e., DDRX operative at high temperatures and CDRX operative at lower temperatures. [5][6][7]12] Understanding the degree to which DRX goes to completion is also important, because a homogenous microstructure is desired for optimal final properties.…”

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

“…To date, the grain refinement due to DRX during hot deformation has been demonstrated in conventional Mg-Al-Zn alloys. [15][16][17][18][19][20][21][22][23][24][25][26][27][28] It has been reported that dynamically recrystallized grain size (DRX grain size) decreases with an increase of Zener-Hollomon parameter (Z-parameter) 29) in several magnesium alloys. 19,24,27,30,31) Watanabe et al have reported that there is initial grain sizes dependence on DRX grain size in AZ61 magnesium alloy.…”

Influence of thermomechanical processing on the grain size, texture and mechanical properties of Mg-Al alloys

“…They observed that the lowest recrystallized volume fraction corresponded to a "c-axis constraint" orientation that is mechanically similar to testing a rolled sample in tension along the rolling direction because in both cases prismatic slip is favoured. Barnett [48] attributes this behaviour to the predominance of prismatic slip favoured in detriment of twinning [48,49]. Myshlyaev et al [45] also emphasized the role of the microstructure heterogeneities, arising from twinning and multiple slip, on inducing DRX nuclei.…”

“…Annealing following LSHR does not result in major texture changes [21,49,90]. An as-extruded plate of an AZ61 alloy, 10 mm in thickness, was processed by severe hot rolling at 400…”

“…Hot working is defined as the application of deformation under the conditions of temperature and strain rate such that recovery and recrystallization processes take place simultaneously with the deformation [44]. Recovery and recrystallization processes in magnesium and its alloys are dependent on several factors such as temperature [45,46], strain rate [47], the operative deformation mechanism [48][49][50][51][52], texture [53][54][55], etc. Several studies were performed to understand the influence of each of these factors by compression or torsion tests [46, 48-51, 56, 57].…”