Deformation and fatigue behavior of lightweight materials

加拿大的汽车工业是制造业GDP的最大贡献者，也是制造业最大的雇主，它在能源、排放和安全等几个关键领域面临着越来越大的压力。交通运输行业的许多材料科学研究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，因为重量减轻10%可以提高6~8%的燃油效率。它最近被描绘成轻量化的“风暴”，是一场材料、工艺和商业模式的革命。这与设计用于改善疲劳，蠕变，冲击或耐腐蚀性的材料一起，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。预计到2020年，轻质材料的全球市场规模将达到1860亿美元，轻质材料的研究与开发已成为材料科学与工程领域最热门的领域之一。镁是最轻的结构金属，被认为是代替较重金属的理想轻质材料。然而，它的广泛应用存在很大的障碍，包括低成形性和强度、疲劳和可靠性、耐腐蚀性、焊接和连接。最近在镁锂合金（称为“不锈钢镁”）和镁纳米复合材料方面的突破性进展为轻量化结构应用铺平了道路。问题仍然是这些新合金在循环变形中的表现，如果发生孪晶和去孪晶，如果各向异性和拉压屈服不对称仍然存在。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之上，并发展对镁合金和其他轻质材料的变形和疲劳的基本理解。具体而言，将审查以下主题：i)将阐明和模拟新镁合金的潜在循环变形和孪生-失孪生机制；ii)将使用一种独特的高温x射线衍射仪评估和分析织构和残余应力，该衍射仪允许现场测量温度的函数；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抗疲劳性能。iv)将开发新的处理方法和模型来削弱纹理和各向异性。这些项目将提高对变形行为的基本理解，为下一代高性能轻量化材料的开发打开大门，为实现轻量化汽车的最终目标做出贡献，保护我们的环境，提高加拿大在全球市场上的竞争力。

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.