마그네슘 합금의 고온 변형에서 용질 원소가 집합조직 형성 거동에 미치는 영향

Abstract

Magnesium alloys have excellent lightweight properties, but their industrial applications are limited by low machinability due to high plastic anisotropy. It is generally believed that this is caused by the texture that develops during processing. Various attempts have been made to control the development of texture. In a previous study, it was confirmed that texture behavior can be changed by controlling processing variables such as strain rate and temperature during processing of the AZ series. Additionally, it was found that texture development could be dramatically controlled by applying other processing methods such as Differential Speed Rolling (DSR), Equal Channel Equal Channel Angular Extrusion (ECAE), or adding rare earth elements to the alloy. However, control through these methods still has the problem of being expensive and time-consuming to apply in industry. Recently, it was confirmed that when Ca is added to magnesium alloy, a texture similar to that of rare earth elements is formed. This means that the development of texture can be sufficiently suppressed not only by adding rare earth elements but also by adding other solute elements. This study investigated the effect of different solute elements on the texture development behavior of magnesium after adding them. The elements added to magnesium are Pb, Al, and Ag, respectively. All of these alloys formed a single-phase structure through rolling and annealing. Afterwards, plane strain compression was performed under the conditions of 723K and 5*10-2s-1. Microstructural analysis and texture measurements were performed via SEM-EBSD. The flow stresses of all three alloys had similar forms. Peak stress showed differences depending on the added elements, but no significant differences were found in terms of microstructure. For all of these alloys, a rapid decrease in average grain size was confirmed by continuous dynamic recrystallization(CDRX) at a strain of -0.4. The texture maintained the same basal texture as before compression, and the maximum pole density was high for the added solute elements in the order Ag > Al > Pb. What is noteworthy here is that the solute elements Ag and Al had recrystallized grain orientations similar to the parent grains, but in Pb, recrystallized grains with more random orientations were formed. This is similar to what occurs with the addition of rare earths and Ca.