Optimizing the strength and ductility of materials through control of microstructure

通过控制微观结构优化材料的强度和延展性

• 批准号: RGPIN-2019-05414
• 负责人: Wilkinson, David
• 金额: $ 2.84万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715533
• 关键词: Optimizing; strength; ductility; materials; through

This research addresses the longstanding issue of ductile fracture in metallic alloys. Premature fracture can be catastrophic in terms of both personal injury and property damage. To prevent failure systems are often over-engineered, making them costlier and less efficient than necessary. For example, auto body panels are thicker than need be, thus impairing vehicle fuel efficiency. An in-depth, fundamentally-based understanding of the mechanisms of ductile fracture and how they are impacted by material microstructure will enable more effective designs that use materials optimally. The progress which I have made on this topic over many years has indeed contributed to the development of more robust models of ductile failure, while the use of x-ray computed tomography (XCT) to visualize the ductile fracture process in detail (something no other group in the world has done) is now embedded in textbooks. Several crucial questions remain unanswered to develop robust models for fracture under complex stress states such as bending, which is integral to processes that control, for example, crash worthiness. Over the next five years I will focus on two main areas. The first is to expand the use of in situ methods that are proving to be invaluable in linking local microstructures to the development of damage, the precursor to ductile fracture. The second is to apply these methods to the study of ductile fracture in two important classes of materials - advanced high strength steels (AHSS) and multi-phase high entropy alloys (HEAs). In situ methods involve the use of microscopy and XCT of samples while they are being deformed. This provides a detailed history of the processes that lead to fracture at a microstructural scale, including load transfer between phases in multi-phase materials. AHSS represent a class of alloys which combine high strength and ductility, making them attractive for automotive applications. However, there have been few investigations of the mechanisms which limit ductility and most of those focus on tensile elongation rather that true failure strain. This is critical since while the former explains limits to some processes such as stretch forming, true failure strain is linked to failure in bending. My group developed microscopic digital image correlation methods to tackle this problem. We now have the capability of applying this to the Generation 3 steels that are emerging as critical to fuel efficient vehicle development. Multi-phase HEAs are a new class of microcomposites that combine two high entropy alloys - one with high ductility, the other with high strength. These materials have only recently been developed; thus there is no understanding of the mechanisms that control their ductility. We need to understand how phase scale and distribution impacts damage accumulation during deformation. This research will enable us to develop optimal microstructures that delay fracture to high strains.

这项研究解决了金属合金中长期存在的延性断裂问题。过早骨折可能会造成灾难性的人身伤害和财产损失。为了防止出现故障，系统通常会被过度设计，从而导致其成本更高、效率更低。例如，车身面板比需要的更厚，从而损害了车辆的燃料效率。对延性断裂机制及其如何受材料微观结构影响的深入、基础的了解将有助于实现更有效地优化材料使用的设计。多年来我在这个主题上取得的进展确实有助于开发更稳健的延性破坏模型，同时使用 X 射线计算机断层扫描 (XCT) 详细可视化延性断裂过程（这是其他方法无法比拟的）世界上的小组所做的）现在已被纳入教科书。在复杂应力状态（例如弯曲）下开发稳健的断裂模型时，仍有几个关键问题尚未得到解答，而弯曲是控制耐撞性等过程中不可或缺的一部分。未来五年我将重点关注两个主要领域。第一个是扩大原位方法的使用，事实证明，这种方法对于将局部微观结构与损伤的发展（韧性断裂的前兆）联系起来非常有价值。第二个是将这些方法应用于两类重要材料——先进高强度钢（AHSS）和多相高熵合金（HEA）的延性断裂研究。原位方法涉及在样品变形时使用显微镜和 XCT。这提供了导致微观结构尺度断裂的过程的详细历史，包括多相材料中各相之间的载荷传递。 AHSS 代表了一类兼具高强度和延展性的合金，使其对汽车应用具有吸引力。然而，对限制延展性的机制的研究很少，大多数研究都集中在拉伸伸长率而不是真正的失效应变上。这一点至关重要，因为虽然前者解释了拉伸成型等某些工艺的限制，但真正的失效应变与弯曲失效有关。我的小组开发了显微数字图像相关方法来解决这个问题。我们现在有能力将其应用于第三代钢材，这些钢材正在成为节能汽车开发的关键。多相 HEA 是一种新型微复合材料，结合了两种高熵合金 - 一种具有高延展性，另一种具有高强度。这些材料最近才被开发出来；因此，人们不了解控制其延展性的机制。我们需要了解相尺度和分布如何影响变形过程中的损伤累积。这项研究将使我们能够开发出延迟高应变断裂的最佳微观结构。