Effect of twin formation by repetitive bending on texture of AZ61 magnesium alloy sheet and improvement of formability

Abstract

Magnesium alloy is the lightest metal among structural metals being used today. However, because the rolled sheets of magnesium alloy are expensive and poor in press formability, the reduction of manufacturing costs and especially the improvement of formability are eagerly required. In order to overcome these problems, the dispersion of texture of rolled sheets caused by twin formation in repetitive bending at room temperature would be effective. In present experiment using the rolled sheets of AZ61 magnesium alloy, the relationship between the times of repetitive bending and the change of texture was investigated. In 4-times repetitive bending, the tensile twin formation and the dispersion of basal plane texture were observed by X-ray diffraction and SEM-EBSD analysis. As the result of formability test, severe 90°V shape bending R/tϭ1 and nearly twice bulging formability were attained in comparison with those of conventional rolled sheets at 473 K. The results of this study suggest that the press formability of rolled sheets of AZ61 magnesium alloy would be effectively improved by repetitive bending at room temperature.

Work-hardening and twinning behaviors in a commercially pure titanium sheet under various loading paths

“…9 and 10, the CP-Ti sheet showed the similar tendency with that of a rolled magnesium alloy sheet [33][34][35][36][37][38][39][40][41][42][43][44] where the f1012g tensile twinning was active under in-plane compression and the detwinning was active when the sheet was subjected to reverse loading from compression to tension. Recently such twinning-detwinning characteristics are used to develop a magnesium alloy sheet with weak texture [57]. The contribution of a strong basal texture to the strong anisotropy observed in CP-Ti sheets [2,3,6,7,9,10], along with the preceding results, suggests that a similar method may be applicable to develop a CP-Ti sheet with a weak texture.…”

Improvement of stretch formability of Mg–3Al–1Zn alloy sheet by high temperature rolling at finishing pass

“…It is therefore a desirable approach to improve the formability of commercial Mg alloys composed of ubiquitous elements by texture control through plastic processing techniques. In recent years, some processing techniques such as asymmetric rolling [3,9], cross rolling [10], repeated unidirectional bending [11], repetitive bending [12], equal channel angular rolling [13], wavy roll forming [14], high temperature annealing before and after warm rolling [15], combination of high temperature and warm rolling [16,17], have been evolved for enhancing the formability of Mg alloy sheets. Compared with those processing techniques, high temperature rolling exhibits different deformation characteristics, e.g.…”

Work-hardening behaviors of magnesium alloy sheet during in-plane cyclic loading

“…Sunaga et al [28] conducted a cyclic bending test on an AZ61 Mg alloy sheet. They found that the intensity ratio of the basal plane decreased with the number of bending cycles owing to the activation of {1 0 1 2} twinning; however, the ratio remained almost unchanged after the fourth cycle.…”