Improving the Mechanical Properties of AZ31 Mg Alloy by High Ratio Extrusion

Abstract

Experiments were conducted both to evaluate the potential for grain refinement, the subsequent mechanical properties at room temperature in samples of AZ31 Mg alloy and also to investigate the relationship between one-step and two-step high ratio extrusion (HRE). The one-step HRE was undertaken using a high extrusion ratio of 70:1 at 250, 300 and 350°C. And the two-step HRE was conducted with an extrusion ratio of 7 for the first step at 250, 300 and 350°C, followed by a second-step extrusion with an extrusion ratio of 10 at 250, 300 and 350°C. The initial grain size in the AZ31 ingot was 100μm and that after one-step HRE became similar to 5μm, after two-step HRE at 250, 300 and 350°C were 2, 4, 7μm, respectively, resulting in superior mechanical properties at ambient temperature. The microstructure of two-step HRE was finer and uniformer than that of one-step HRE and the strength of one-step and two-step HRE were similar, moreover, the elongation of one-step HRE was improved markedly than that of two-step HRE. Dynamic recrystallization and adjacent grain broking during HRE is introduced to explain the effects of one-step and two-step HRE on the microstructure and mechanical properties of AZ31 Mg alloy. The current results imply that the simple HRE method might be a feasible processing method for industry applications, and the multiply steps extrusion are effective to fabricate high strength of fine grained hcp metals.

Microstructure evolution in magnesium alloy AZ31 during cyclic extrusion compression

“…It is also different to the recrystallization necklace of fine grains associated with the repeated nucleation of fine grains starting from the original grain boundaries [21], which is commonly obtained in Cu, Ni and ␥-Fe during partial discontinuous dynamic recrystallization (DDRX) [21]. However, for heavily strained AZ31, recrystallization is totally complete at 573 K [22]. After CEC the network shape structure is divided and more network shape structures are formed with increasing strain (see Fig.…”

An Ebsd Study on the Microstructure and Texture Evolution of Az31 Magnesium Alloy During Accumulative Roll-Bonding

“…¡ 4 Ð (0002) Ü¡× . ¤ Õ Ð AZ31 ×È , µ 573 K ¤º¤ [20] . §¸ Ð Ù µ ¢È Ð ÄÎ ¨Û ¿, §ÄΨРÈÃ ß Ó § Õ Ê, ß ¬ ÄÕºÐÈ.…”

Development of a novel high straining backward extrusion process

“…Recently, extensive studies have been performed for various new techniques, based on the extrusion process, for imposing a higher effective strain and a better strain homogeneity. The conventional direct extrusion process with a high ratio in one/two steps [8,9] and the hydrostatic extrusion with an extra-high ratio [10] were studied. The multiple direct extrusion (MDE) process was earlier proposed [11] as a new technique for grain refinement.…”