1、Cold stamping formability of AZ31B magnesium alloy sheet undergoing repeated unidirectional bending processLei Zhanga,b, Guangsheng Huanga,b, * , Hua Zhanga,b , Bo Song a,ba National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030, Chinab College of Material
2、Science and Engineering, Chongqing University, Chongqing 400030, China-a r t i c l e i n f o-Article history:Received 11 April 2010Received in revised form 7 November 2010Accepted 28 November 2010Available online 7 December 2010-a b s t r a c t-The repeated unidirectional bending (RUB) process was c
3、arried out on an AZ31B magnesium alloy in order to investigate its effects on the cold stamping formability. The limiting drawing ratio (LDR) of the RUB processed magnesium alloy sheet with an inclination of basal pole in the rolling direction can reach 1.5 at room temperature. It was also conrmed t
4、hat cell phone housings can be stamped successfully in crank press using the RUB processed AZ31B magnesium alloy sheet. The improvement of the stamping formability at room temperature can be attributed to the texture modications, which led to a lower yield strength, a larger fracture elongation, a s
5、maller Lankford value (r-value) and a larger strain hardening exponent (n-value). 2010 Elsevier B.V. All rights reserved.Keywords: Magnesium alloy sheet;RUB;Texture;Stamping formability；Cell phone housing1. IntroductionNowadays, the products of magnesium alloys, mainly formed by casting and die-cast
6、ing, are used in the aerospace, automobile, civilian household appliances. Compared with casting and die-casting, plastic forming technology seems to be more attractive because of its competitive productivity and performance. Among the fabricationprocesses of plastic forming, stamping of magnesium a
7、lloy sheets is especially important for the production of thin-walled structural components (Chen and Huang, 2003). However, magnesium alloy sheets have low ductility at room temperature due to itsstrong (0002) basal texture, as shown in the literature (Doege and Droder, 2001). Mori and Tsuji (2007)
8、 investigated cold deep drawing of commercial magnesium alloy sheets, they demonstrated that the limiting drawing ratio of rolled AZ31 magnesium alloy sheetsannealed at 773 K can reach 1.7. Mori et al. (2009) have shown that a two-stage cold stamping process are also helpful for forming magnesium al
9、loy cups. Watanabe et al. (2004) suggested the ductility of magnesium alloy sheets can be improved by reducing (0002) basal texture at room temperature. The limiting drawing ratio for the cold deep drawing of commercial magnesium alloy sheets can be improved from 1.2 to 1.4 by reducing (0002) basal
10、plane texture (Iwanaga et al., 2004). It is well-known that equal channel angular pressing (ECAP) is an effective method to obtain a tilted basal texture, which improved signicantly the tensile elongation (Kim et al., 2003). But it is hard for ECAP to fabricate thin sheet. Recently, it is reported t
11、hat a rolled magnesium alloy sheet, with a tiled texture obtained by cross-roll rolling (Chino et al., 2006) and different speed rolling (DSR) process (X.S. Huang et al., 2009), exhibit higher stamping formability compared with a rolled magnesium alloy sheet by normal-roll rolling. It is therefore i
12、mportant to improve the formability at room temperature for a wide use of magnesium alloy sheets by changing or weakening the basal texture.Older versions of the ASM Metals Handbook (1969) on forming refer to a “special bending sheet,” which was produced by Dow Magnesium. The special bending sheet w
13、ith a modied crystallographic texture, had better forming characteristics than conventional AZ31 sheet. Previous study (G.S. Huang et al., 2009) revealed that the RUB process also improved the stretch forming of magnesium alloy sheets by weakening basal texture of sheets. The Erichsen values of the
14、RUB processed sheet signicantly increased from 3.53 to 5.90 in comparison with the cold-rolled magnesium alloy sheet. However, up to now, few researchers made efforts to study the cold stamping formability of the magnesium alloy sheets. Cold stamping products, such as housings of laptop computers an
15、d cell phones, have not been reported in other investigations. Hence, it is important to investigate the cold deformation behaviors so as to establish fundamental knowledge of the cold forming technology of magnesium alloy.In this paper, an investigation of the drawability of RUB processed AZ31 magnesium alloy sheet was performed at room temperature using uniaxial tensile tests, deep drawing and cold stamping of a cell phone housing. The performance of RUB sheet was compared with that of the as-received sheet.2. Experimental mate
