Enhancement of ductility in Mg-3Al-1Zn alloy with tilted basal texture by electropulsing
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oyi Tanga) Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
Paul K. Chub) Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
Yanbin Jiang Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China (Received 10 July 2009; accepted 16 September 2009)
The microstructure and texture evolution in a cold-rolled AZ31 magnesium alloy during electropulsing treatment (EPT) are investigated and correlated with the mechanical properties. The microstructure is effectively refined, and a tilted basal texture develops gradually during EPT. The yield stress in the treated samples is lower than that in the cold-rolled sample, indicating that texture softening is dominant over strengthening because of grain refinement. The phenomenon is primarily the result of the tilted basal texture. EPT improves the tensile ductility of the EPT samples significantly, albeit slightly compromising the tensile strength. The mechanism of the microstructure evolution during electropulsing is discussed from the viewpoint of grain-boundary motion. Moreover, the ductility enhancement is discussed in terms of the deformation mechanism and texture of the Mg alloy. I. INTRODUCTION
Wrought magnesium alloys are potential lightweight structural materials in the automotive and other industry because of their low density and high specific strength.1 However, the poor ductility of Mg alloys as a result of the hexagonal crystal structure and associated lack of sufficient slip systems at room temperature have hindered wider applications. Grain refinement is known to significantly improve the ductility and formability of magnesium alloys.2–4 By adopting the novel technique of electropulsing treatment (EPT), grain refinement can be achieved in Mg alloys5–7 to improve the mechanical behavior via the Hall–Petch effect.6,8 The mechanical properties of Mg alloys depend on the texture as well as grain size.3,9 Sambasiva and Prasad9 studied the influence of the texture on grain-boundary strengthening in hot-rolled magnesium and pointed out that the texture affected the Hall–Petch constants via its effect on the orientation factors resulting Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2009.0436 3674
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J. Mater. Res., Vol. 24, No. 12, Dec 2009 Downloaded: 13 Mar 2015
from the critical resolved shear stress (CRSS) in the individual slip systems. Mukai et al.3 performed ECAE on AZ31 magnesium alloy and observed a peculiar texture with the basal plane orientation inclined 45 to the extrusion direction. Owing to this texture development, their samples exhibited high ductility of 45% even at room temperature. Accordingly, texture control is one of the effective methods to improve the mechanical properties of Mg alloys.3,10–12 Our previous study7 revealed that during EPT, the recrystallized grains
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