Mechanical Properties and Structure Evolution of the Az91 Magnesium Alloy After Hot Rolling and Annealing

Abstract

Mechanical properties and structure evolution of the AZ91 magnesium alloy after hot rolling and annealing Właściwości mechaniczne oraz struktura stopu AZ91 po walcowaniu na gorąco i wyżarzaniu AbstractThe AZ91 magnesium alloy was processed up to 87.5% of total thickness reduction in several thermodynamic routes, consisted of hot rolling and intermediate annealing. The hot-rolling process was performed at a high strain rate equal to 1.6 s −1 and at a temperature of 430°C. The intermediate annealing was performed at 430°C for 15 minutes after each route. It was found that, during hot rolling, the hardness of the material increased from 32 HV to 40 HV, and the structure investigations showed a huge amount of twins formed inside the grains (which were not observed after annealing). Tensile tests have shown strong anisotropy in mechanical properties of the "as-rolled" samples dependent on the orientation between tension direction (TD) and rolling direction (RD). The samples with TD perpendicular to RD proved higher ultimate tensile strength (UTS) and (on the other hand) worse plastic properties as compared to the samples with TD parallel to RD. The annealing has an effect on the reduction of mechanical properties anisotropy. X-ray investigations have shown texture changes from the basal type with the additional (0001) <1120> component for "as-rolled" samples to the texture with the main (0001) <1010> component for annealed samples. The texture changes had a great impact on the anisotropy of mechanical properties of the investigated AZ91 magnesium alloy.

Structure and Properties of Hot-Rolled and Annealed Az61 Magnesium Alloy

“…The texture effects described in the present study have a great effect on the plastic and mechanical properties of magnesium alloys after hot rolling and annealing, and this has been reported before [5,11]. The texture changes observed in the present study during annealing after hot rolling of the AZ61 magnesium alloy may help us better understand the deformation processes in magnesium alloys and to design a deformation scheme composed of several thermodynamic passes for the effective processing of magnesium alloys.…”

“…The B "asrolled" sample where TD is perpendicular to RD is very similar to Sample A "as-rolled. " In this case, no strong anisotropy of mechanical properties was reported (as opposed to AZ91 after hot rolling, for example) [11]. Partially, the reason for this is the formation of a different texture in the case of the present study, which will be discussed later in this paper.…”

“…5c) weak (0001) <1120> and {1120} fiber texture components can be observed. The changes in the texture components may have great impact on the plasticity of deformed magnesium and its alloys due to the influence on the slip system activity in a particular grain [4,5,11]. In the magnesium alloy with the basal fiber texture (the case of AZ61 after hot rolling in the present study), the grains are oriented in a way that the c-axis is perpendicular to the rolling direction and parallel to the normal direction (ND); see Figure 1.…”

“…In the magnesium alloy with the basal fiber texture (the case of AZ61 after hot rolling in the present study), the grains are oriented in a way that the c-axis is perpendicular to the rolling direction and parallel to the normal direction (ND); see Figure 1. This orientation hampers the activation of the basal slip systems during such processes as rolling or tension and may lead to the failure of AZ61 during rolling [4,11,13]. However, after annealing AZ61 for 1 hour, the samples are free of twins, and most of the grains are oriented in such a way that the <1120> direction is parallel and <1010> is perpendicular to the RD.…”