Deformation and fatigue behavior of lightweight materials

加拿大汽车业是制造业GDP的最大贡献者，也是最大的制造业雇主，在能源、排放和安全等几个关键领域面临着越来越大的压力。交通运输业的大部分材料科学工作都是由对燃油经济性和气候变暖排放的严格监管推动的。轻量化是应对这些挑战的关键策略，因为10%的重量减轻会带来6%~8%的燃油效率提高。最近，它被描绘成一场轻量化的材料、工艺和商业模式革命的“风暴”。这与用于改善疲劳、蠕变、冲击或腐蚀性能的材料一起，已被确定为解决国家和全球重大挑战的六个关键领域之一。轻质材料的研发，预计到2020年全球市场规模将达到1860亿美元，已成为材料科学和工程领域最热门的领域之一。镁是最轻的结构金属，被认为是替代较重金属的理想轻质材料。然而，它的广泛应用还有很大的障碍，包括成形性和强度低、疲劳和可靠性、耐腐蚀性、焊接和连接。镁锂合金“不锈钢镁”和镁纳米复合材料的最新突破性发展为轻量化结构应用铺平了道路。问题仍然是，如果发生孪生和去孪晶，以及各向异性和拉伸-压缩屈服不对称是否仍然存在，这些新合金在循环变形中的表现如何。拟议的研究旨在解决这些关键问题和障碍，建立在申请人在该领域的开创性和广泛的研究经验和知识的基础上，并对镁合金和其他轻质材料的变形和疲劳有一个基本的了解。具体地说，将研究以下主题：i)将阐明和模拟新型镁合金中潜在的循环变形和孪生-去孪生机制，ii)将使用独特的高温X射线衍射仪来评估和分析织构和残余应力，该仪器允许作为温度的函数进行现场测量，iii)将研究基于“多材料”轻量化策略的不同焊接接头的变形和疲劳抗力，以及iv)将开发新的加工方法和模型来削弱织构和各向异性。这些项目将提高对变形行为的基本了解，为下一代高性能轻质材料的开发打开大门，有助于实现制造轻量化汽车的最终目标，保护我们的环境，并提高加拿大在全球市场的竞争力。

Canada's automotive industry the biggest contributor to manufacturing GDP and largest manufacturing employer is facing mounting pressures in several key areas including energy, emissions, and safety. Much of the materials science efforts in the transport industry is driven by the stringent regulation of fuel economy and climate-warming emissions. Lightweighting is a key strategy to address these challenges, since a 10% weight reduction results in a 6~8% fuel-efficiency gain. It has recently been portrayed as the "storm" of lightweighting a revolution in materials, processes, and business models. This, along with materials designed for improved fatigue, creep, impact, or corrosion resistance, has been identified as one of six areas critical to solving national and global grand challenges. The research and development of lightweight materials, which are predicted to reach a global market of US$186 billion by 2020, have become one of the hottest areas in materials science and engineering. Magnesium is the lightest structural metal and is regarded as an ideal lightweight material to replace heavier metals. However, there are big hurdles to its wide applications, including low formability and strength, fatigue and reliability, corrosion resistance, welding and joining. Recent ground-breaking developments in magnesium-lithium alloys called "stainless magnesium" and magnesium nanocomposites pave the way for lightweight structural applications. The questions remain how these new alloys behave during cyclic deformation, if twinning and detwinning occur, and if the anisotropy and tension-compression yield asymmetry still exist. The proposed research is aimed to address these key questions and obstacles building upon the applicant's pioneering and extensive research experience and knowledge in this area, and develop a fundamental understanding of deformation and fatigue of magnesium alloys and other lightweight materials. Specifically, the following topics will be examined: i) the underlying cyclic deformation and twinning-detwinning mechanisms in new magnesium alloys will be elucidated and modeled, ii) the texture and residual stresses will be evaluated and analyzed using a unique high-temperature X-ray diffractometer which permits in-situ measurements as a function of temperature, iii) the deformation and fatigue resistance of dissimilar welded joints based on the "multi-material" lightweighting strategies will be examined, and iv) new processing approaches and models will be developed to weaken textures and anisotropy. These projects will improve fundamental understanding of deformation behavior, open the door to the development of next-generation high-performance lightweight materials, contribute to achieving the ultimate goal of constructing lightweight vehicles, protecting our environment and enhancing Canadian competitiveness in the global market.