Design of Twinning Induced Plasticity (TWIP) Magnesium Alloys

镁合金是最轻的结构金属，密度比铝合金轻34%，因此在迫切需要提高燃油效率的汽车和航空航天应用中非常有吸引力。然而，通过对铝合金有效的传统合金设计方法来强化镁合金已被证明是困难的。镁合金的延展性也较低，导致其在室温下成形性较差。镁合金的低强度和低延展性限制了镁合金的工业应用，需要新的合金设计和加工策略来克服这些障碍。该奖项支持镁合金设计新方案的基础研究，该方案与传统方法不同，有可能产生高强度、延展性的镁合金。计算机模拟和实验相结合将确定合金元素，可以导致高强度和延展性。这项研究的结果将为新型镁合金的设计提供指导，从而提高车辆的燃油效率并减少排放。在教育方面，本计画提供一个机会，让工科学生进行合金设计的电脑模拟与实验研究。在高锰浓度的钢中，孪生诱发塑性非常有效地实现了高强度和延展性，其中机械孪生是应变诱发的，有助于塑性流动和硬化，从而产生优越的机械性能。与之形成鲜明对比的是，尽管镁合金可以激活大量孪晶，但由于这些合金在低应力水平下由应力诱发孪晶，因此缺乏对孪晶诱导塑性的应用。因此，为了使镁合金引入孪晶诱导塑性，必须提高孪晶临界应力。在本研究项目中，将通过第一性原理计算来确定对镁合金的c/a比和变形孪晶过程中原子变换的能垒有显著影响的合金元素。这些参数控制孪晶形核和生长的临界应力。确定这些合金元素后，将进行合金合成和热机械加工，以获得最佳的力学性能。这一策略为高性能镁合金的可持续设计和加工打开了一扇新的窗口，而无需求助于昂贵和外来的合金元素。

Magnesium alloys are the lightest structural metals with densities near 34% lighter than aluminum alloys, and are thus very attractive for automotive and aerospace applications where improved fuel efficiency is urgently needed. However, strengthening magnesium alloys through the conventional alloy design approaches that are effective for aluminum alloys has proved difficult. The ductility of magnesium alloys is also low, which results in poor formability at room temperature. The low strength and ductility have limited the industrial applications of magnesium alloys, and new alloy design and processing strategies are needed to overcome these barriers. This award supports fundamental research for a new scheme for magnesium alloy design that departs from conventional approaches, and has the potential to lead to high-strength, ductile magnesium alloys. Computer simulations and experiments will be combined to identify alloying elements that can lead to high strength and ductility. The outcome of this research will provide guidelines for design of new magnesium alloys, leading to improved fuel efficiency of vehicles and reduced emissions. Educationally, this project provides an opportunity for engineering students to conduct computer simulations and experimental studies for alloy design.Twinning induced plasticity is very effective in achieving high strength and ductility in steels with high manganese concentrations in which mechanical twinning is strain-induced and contributes to the plastic flow and hardening, resulting in superior mechanical properties. In stark contrast, application of twinning induced plasticity is lacking in magnesium alloys, despite the fact that profuse twinning can be activated, because twinning is stress-induced at low stress levels in these alloys. Thus, to introduce twinning induced plasticity into magnesium alloys, the critical stress for twinning must be increased. In this research project, first principles calculations will be performed to identify alloying elements that have significant influences on the c/a ratio of magnesium alloys and the energy barrier for atomic shuffling during deformation twinning. These parameters control the critical stress for twin nucleation and growth. After these alloying elements are identified, alloy synthesis and thermomechanical processing will be conducted to achieve the optimal mechanical properties. This strategy opens a new window for sustainable design and processing of high performance magnesium alloys without resorting to expensive and exotic alloying elements.