Constitutive Behavior of Commercial Grade ZEK100 Magnesium Alloy Sheet over a Wide Range of Strain Rates
- PDF / 4,431,233 Bytes
- 17 Pages / 593.972 x 792 pts Page_size
- 70 Downloads / 247 Views
CTION
MAGNESIUM alloys have attracted increased attention in recent years as lightweight materials for the transportation industry. Indeed, the low density of magnesium and its relatively high specific strength make it an excellent candidate for applications where reduction of structural weight and fuel consumption are common challenges. However, present applications of magnesium alloys are mostly limited to extruded and cast parts[3] since magnesium sheet alloys have limited formability at room temperature.[4] The limited formability is due to the hexagonal close-packed (hcp) structure of magnesium alloys, such as AZ31B sheet, which offers only a limited number of slip systems that are active at room temperature due to the strong basal crystallographic texture.[5,6] The formability can be increased by forming at elevated temperatures[7–10]; however, warm forming requires more complex tooling and lubrication strategies which increase the cost of the forming operation. SRIHARI KURUKURI, Postdoctoral Researcher, MICHAEL J. WORSWICK, Professor, Tier 1 Canada Research Chair, and ALEXANDER BARDELCIK, Research Associate, are with the Department of Mechanical & Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada. Contact e-mail: [email protected] RAJA K. MISHRA, Technical Fellow, and JON T. CARTER, Staff Researcher, are with Chemical and Materials Systems Laboratory, General Motors R & D, Warren, MI 48090. Manuscript submitted August 2, 2013. Article published online April 16, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
One of the techniques used to improve the room temperature formability of magnesium alloys is the addition of rare-earth elements such as Ce, Nd, Y, and Gd, for example, which have been shown to weaken the basal texture.[11–16] Rare-earth addition modifies and weakens the basal texture of a rolled Mg alloy, resulting in an enhancement of formability as well as reduced mechanical anisotropy at room temperature. Bohlen et al.[11] investigated the rolling texture and anisotropy of several Mg-Zn alloy sheets with different levels of Zn and rare-earth additions. They reported that the overall texture strength and the basal pole intensity aligned with the sheet normal direction was lower for rare-earth containing alloys than for conventional alloys. The anisotropy of the yield and flow strengths was reversed in comparison to conventional alloys, and the planar anisotropy or Lankford coefficient (R value) was reduced to unity. These changes were related to the fact that the dominant texture components in the rare-earth Mg-Zn alloys placed more grains in favorable orientations for basal slip and tensile twinning. Al-Samman and Li[16] studied texture modifications in Mg alloys due to rare-earth additions such as Gd, Nd, Ce, La and found that different rare-earth elements have different solid solubility and give rise to distinct microstructures. Mg alloy sheets with La, Nd, Gd have less anisotropy and ductility than those with Ce. The R value for all o
Data Loading...
