Secondary Processing of AZ31 Magnesium Alloy Concomitant with Grain Growth or Dynamic Recrystallization

Abstract

Plastic formability in the secondary processing of an AZ31 magnesium alloy was investigated using fine-grained and relatively coarsegrained materials, respectively. To produce components for mobile electric appliances, boss formability was examined at a relatively low temperature of 523 K. The boss with a height of 14 mm was successfully formed in fine-grained material under a nominal forming pressure of 582 MPa in 5 s. Analysis of the boss forming revealed that the forming occurred under the high-strain-rate superplastic condition. The grain size in the boss region was slightly coarsened, probably as a result of strain-induced grain growth, which is a widespread property of superplastic flow. On the other hand, even in the coarse-grained material, a relatively high boss height of 5 mm was obtained under the same forming condition. After the boss forming, grain refinement was observed in the coarse-grained material. It was suggested that the coarse-grained materials exhibited relatively high formability because of dynamic recrystallization. It was concluded that plastic forming concomitant with grain growth was more effective than that concomitant with grain refinement in AZ31 magnesium alloy. An empirical equation to perform plastic forming under the condition concomitant with grain growth was developed.

Superplasticity and superplastic forming of Mg–Al–Zn alloy sheets fabricated by strip casting method

“…Takara et al [10] proposed that the critical grain size, d crit , above which grain refinement occurs and below which grain growth occurs during deformation, could be given by the following empirical equation for the AZ31 alloy:…”

Fracture toughness in a rolled AZ31 magnesium alloy

“…The basal texture also affects the mechanical properties, strength and/or elongation-to-failure, at room temperature in a wrought magnesium alloy [13][14][15][16][17][18]. In spite of the strong basal texture in rolled magnesium alloys, the investigation of the fracture toughness is very limited [19].…”

Effect of Ultrasonic Vibration Pretreatment on Microstructural Evolution and Mechanical Properties of Extruded AZ91 Alloy

“…The recrystallized grain sizes in magnesium alloys tend to be affected drastically by the initial grain sizes. [20][21][22] Thus, one of the reasons for the different grain structures, which are expressed by means such as the average value and /or the distribution of the grain size, is related to the initial structures. In addition, since the billet was kept in the container for several minutes before the extrusion, fine precipitates, which are sufficient to form the present condition, should prevent the grain growth.…”