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.

这项研究解决了长期存在的问题，在金属合金的韧性断裂。过早骨折可能会造成灾难性的人身伤害和财产损失。为了防止故障，系统往往被过度设计，使其成本更高，效率更低。例如，汽车车身面板比需要的厚，从而损害车辆的燃料效率。对韧性断裂机制以及它们如何受材料微观结构影响的深入、基础性理解将使更有效的设计能够最佳地使用材料。多年来，我在这一课题上取得的进展确实有助于开发更可靠的延性破坏模型，而使用X射线计算机断层扫描（XCT）来详细可视化延性断裂过程（世界上没有其他小组这样做）现在已经嵌入教科书中。几个关键的问题仍然没有答案，以开发强大的模型，在复杂的应力状态下，如弯曲，这是不可分割的过程，控制，例如，碰撞价值的断裂。在未来五年里，我将重点关注两个主要领域。首先是扩大使用原位方法，这种方法在将局部微观结构与损伤的发展联系起来方面证明是非常宝贵的，而损伤是韧性断裂的前兆。第二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（HEAs）的韧性断裂研究。原位方法涉及在样品变形时使用显微镜和XCT。这提供了一个详细的历史过程，导致在微观结构尺度上的断裂，包括在多相材料的相之间的负载转移。AHSS代表了一类结合了高强度和高延展性的联合收割机合金，使其在汽车应用中具有吸引力。然而，很少有研究限制延性的机制，而且大多数研究都集中在拉伸伸长率而不是真正的破坏应变。这是至关重要的，因为虽然前者解释了某些工艺的限制，如拉伸成形，但真正的失效应变与弯曲失效有关。我的团队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，这些钢材对节能汽车的开发至关重要。多相HEAs是一种新型的微复合材料，其结合了联合收割机两种高熵合金-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，因此对控制其延展性的机制还不了解。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最佳的微观结构，延迟断裂到高应变。