Development of a magnesium alloy sheet with enhanced formability for vehicle lightweighting

镁合金具有低密度和高比刚度，为车辆轻量化提供了巨大的可能性。与它们的使用相关的问题之一是它们在室温下的低成形性。温度越高，由于激活了额外的滑移系统，它们的成形性就得到了改善。然而，在高温下成形需要额外的工具和能源成本，并且延长了周期时间。提高镁合金成形性的另一种方法是控制其织构和组织。随机织构和细晶导致孪晶的减少和成形性的增加。通常，通过添加稀土元素(REE)作为合金元素可以获得更多的随机织构。然而，这些元素的成本很高，而且与它们的生产、加工和利用有关的许多环境和健康问题。近年来，非对称轧制作为一种在各种金属板材上获得微细组织的方法已被研究。在这一过程中，上下轧辊之间的速度差异会产生剪应力，从而促进再结晶，从而生产出更细小的板材。使用该工艺生产的板材具有更好的成形性和良好的机械性能。在本项目中，将对非对称轧制生产的镁薄板的成形性进行研究。将使用两种常见合金(AZ31和ZEK100)作为基准，并与将开发的一种新合金进行比较。这种新合金是由德国合作伙伴开发的，目的是向汽车行业提供具有更好的成形性和机械性能的轻型合金(合金中铝的比例增加)。该项目中进行的成形性研究将使我们的加拿大工业合作伙伴能够评估基准镁合金板材以及新合金板材的潜在用途，这些板材用于在常温和中温(高达250°C)下冲压生产汽车零部件。随着对轻量化汽车零部件的需求不断增长，新材料和新技术的研究项目成为我们行业在这个竞争激烈的市场中保持领先地位的必备条件。

With their low density and high specific stiffness, magnesium alloys offer great possibilities for vehiclelightweighting. One of the issues associated with their use is their low formability at room temperature. Athigher temperatures, their formability is improved due to the activation of additional slip systems. However,forming at high temperatures involves additional tooling and energy costs and lengthens the cycle time.Another way to improve magnesium formability is to control its texture and microstructure. A random texture,as well as fine grains, lead to a reduction of twinning and an increase in formabilty. Typically, more randomtextures are obtained by the addition of rare earths elements (REEs) as alloying elements. However, theseelements are costly and there are many environmental and health issues associated to their production,processing, and utilization. Recently, asymmetric rolling has been studied as a way to produce finemicrostructures in various metal sheets. During this process, the difference in speed between the top andbottom rollers induces shear stresses that promote recrystallization, therefore producing sheets with finergrains. Sheets produced using this process show improved formability and good mechanical properties. In thisproject, the formability of magnesium sheets produced by asymmetric rolling will be studied. Two commonalloys (AZ31 and ZEK100) will be used as a baseline, and compared with a new alloy that will be developed.This new alloy is being developed by German partners with the aim of offering, to the automotive sector, alight alloy with improved formability and mechanical properties (with an increased proportion of aluminium inthe alloy). The formability studies performed in this project will allow our Canadian industrial partner to assessthe potential uses of the baseline magnesium alloy sheets, as well as the new alloy sheets, for the production ofautomotive parts by stamping at room temperature and moderate temperatures (up to 250°C). With thegrowing demand for lightweight automotive components, research projects on new materials and technologyare mandatory for our industries to maintain their leadership in this highly competitive market.