Squeeze Casting of Wrought Mg Alloys for Lightweight Structural Automotive Components

2015年北美制造的汽车的平均镁含量为5公斤，而2000年每辆汽车的镁含量为3公斤。到2025年，由于其轻量化特性，镁的使用量预计将增加两倍，达到每辆车约15公斤。目前，镁合金汽车零部件主要采用传统的铸造镁合金，通过传统的高压压铸工艺（C-HPDC）制造。铸造缺陷会影响C-HPDC合金的力学性能，降低其强度和塑性。C-HPDC Mg部件由于进入模腔的熔融合金的严重湍流而易于具有高水平的孔隙率。由于常规铸造镁合金的机械性能不足，在车辆的关键区域（包括底盘、车身框架和悬架）中使用C-HPDC镁铸件存在重大限制。关键区域的结构部件需要高强度、高延展性和改进的耐腐蚀性，并且能够在循环载荷和腐蚀环境中发挥作用。为了将镁应用扩展到汽油或柴油动力车辆（GDV）或电池动力电动车辆（BEV）的结构和安全关键部件，如转向节、控制臂、副车架、单体式车身、门框和安全带支架，这些部件在使用过程中会经历高循环机械载荷，开发具有成本效益的制造工艺对于生产轻质高完整性结构汽车部件至关重要。低成本变形镁合金具有足够的延展性和强度，以确保轻质高完整性结构应用具有一致的优异塑性和高强度。该提案的长期目标是利用挤压铸造（SC）的廉价锻造镁合金的独特工程性能和质量，用于汽车应用，特别是GDV或BEV中的高完整性结构部件。拟议的研究计划将采用一个系统的设计方法，指导全面的低成本SC变形镁合金（LSCWMAs）的高塑性和强度的加工-组织-性能关系。未来五年的短期目标是：（I）开发低成本变形镁合金的挤压铸造工艺和（II）评估和表征以及LSCWMA的优化。这项新技术将使加拿大在高完整性轻质结构应用的新兴市场中处于领先地位。加拿大的原始设备制造商（福特、丰田、通用、本田和克莱斯勒）需要为其GDV和BEV提供高完整性的轻质结构应用。安大略拥有世界上最大的镁压铸公司Meridian。为潜在的先进产品开发新的镁工艺将导致加拿大制造的镁基铸件的增加，以及加拿大增值轻质产品在全球范围内的使用扩大。

The average Mg content in 2015 North America built cars was 5 kg, compared with an increase from 3 kg per vehicle in 2000. By 2025, the usage of Mg is expected to triple to about 15 kg per vehicle due to its lightweight property. The current Mg automotive components are mainly manufactured by conventional high pressure die casting processes (C-HPDC) with the conventional cast Mg alloys. The mechanical properties of C-HPDC alloys are affected by casting defects, which reduce the strength and ductility. C-HPDC Mg components are prone to high levels of porosity because of severe turbulence of the molten alloy that enters the die cavity. There is a major limitation on the use of C-HPDC Mg castings in critical areas of the vehicle including chassis, body frame and suspension due to the inadequate mechanical properties of the conventional cast Mg alloys. The structural components in the critical areas require high strength, high ductility and improved corrosion resistance, and are capable of functioning in cyclic loading and corrosive environment. To expand Mg applications into structural and safety-critical parts of both gasoline or diesel-powered vehicles (GDVs) or battery-powered electric vehicles (BEVs), such as knuckles, control arms, subframe, unibody, door frame and seat belt brackets, which experience a high cyclic mechanical loading during service, the development of cost-effective manufacturing processes is essential to produce lightweight high-integrity structural automotive components. Low-cost wrought Mg alloys possess sufficient ductility and strengths to ensure that lightweight high-integrity structural applications have consistent excellent plasticity and high strengths. The long term objective of this proposal is to exploit the unique engineering performance and qualities of inexpensive wrought Mg alloys with squeeze casting (SC) for automotive applications, particularly high-integrity structural components in GDVs or BEVs. The proposed research program will employ a systematic design approach guided by comprehensive processing-microstructure-property relationships of the low-cost SC wrought Mg alloys (LSCWMAs) with high plasticity and strengths. The short term objectives in the next five years are: (I) development of squeeze casting processes for low-cost wrought Mg alloys and (II) evaluation and characterization as well as optimization of the LSCWMAs. This new technology will put Canada at the leading edge in emerging markets for high-integrity lightweight structural applications. The OEMs present in Canada (Ford, Toyota, GM, Honda and Chrysler) need high-integrity lightweight structural applications for their GDVs and BEVs. Ontario hosts the world's largest Mg die casting company, Meridian. The development of new Mg processes for potential advanced products will lead to an increase in Mg-based castings made in Canada as well as an expansion of world-wide use of Canadian value-added lightweight products.