Cost-effective lightweight complex-shaped structural components made of magnesium: A hybrid manufacturing paradigm

汽车行业正在经历一个重大转变，在车辆设计中考虑使用轻质材料，以提高燃油/动力经济性。镁（Mg）具有低密度，密度约为铝的三分之二，高比强度和良好的疲劳性能，近年来受到了广泛的关注。然而，由于镁合金在室温下的成形性有限，限制了其在汽车结构件中的应用。铸造和锻造已被考虑用于制造疲劳关键部件，如转向和悬挂部件。铸造能够以相对较低的成本制造复杂的形状，但可能导致缺陷和较差的机械性能。另一方面，锻造提供了优异的机械性能，但仅限于简单的形状，或者需要多阶段锻造，在阶段之间有闪光修整。为了充分利用铸造的成本效益和锻造件优越的材料性能，本研究提出了一种新的镁合金混合铸造后锻造方法。在这种独特的方法中，首先将零件浇铸成具有工程材料分布的最佳中间形状，然后在接近再结晶温度下锻造成最终形状。本研究的总体目标是科学地了解铸件的初始材料分布和性能对锻造过程中组织和织构演变及其最终性能的影响。这项研究将开发科学知识和使能技术，用于制造汽车应用的Mg复杂形状的结构件。

Automotive industries are going through a major shift in using lightweight materials in vehicle design considerations to improve fuel/power economy. Magnesium (Mg) with low density, approximately two-thirds as dense as aluminum, high specific strength, and good fatigue properties, has received significant attention in the recent years. However, due to limited formability of Mg at room temperature, its application to automotive structural components has been limited. Casting and forging have been considered for manufacturing of fatigue-critical parts such as steering and suspension components. Casting enables manufacturing of complex shape at relatively low cost but can result in defects and poor mechanical properties. On the other hand, forging provides excellent mechanical properties but is limited to simple shapes, or requires multiple stage forging with flash trimming in between stages. To leverage the cost-effectiveness of casting and superior material properties of forged parts, a novel hybrid cast followed by forging of Mg alloys is proposed in this research. In this unique method the part is first cast to an optimum intermediate shape with engineered material distribution and then forged into its final shape at near re-crystallization temperature. The overall objective of this research is to develop a scientific understanding of the impact of the initial material distribution and properties of cast on the microstructure and texture evolution during the forging process and its final properties. This research will develop the scientific knowledge and enabling technologies that will be used to manufacture Mg complex-shaped structural parts for automotive applications.