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.

这项研究涉及金属合金中延性裂缝的长期问题。就人身伤害和财产损害而言，过早骨折可能是灾难性的。为了防止故障系统经常被过度设计，使它们的昂贵和效率低于必要。例如，汽车车身面板比需要厚，从而损害了车辆燃油效率。深入的，从根本上基于对延性骨折机制的理解以及它们如何受到材料微观结构的影响，将实现更有效的设计，以最佳地使用材料。我多年来在这个主题上取得的进展确实有助于开发更健壮的延性故障模型，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（世界上没有其他团体所做的事情）现在嵌入了教科书中。在复杂的压力状态（例如弯曲状态）下，几个至关重要的问题仍未得到解决，以开发出良好的裂缝模型，弯曲状态是控制崩溃值得的流程不可或缺的一部分。在接下来的五年中，我将专注于两个主要领域。首先是扩大对原位方法的使用，这些方法在将局部微观结构与损伤的发展（延性裂缝的前体）联系起来是无价的。第二个是将这些方法应用于两种重要类型材料中的延性裂缝的研究 - 先进的高强度钢（AHS）和多相高熵合金（HEAS）。原位方法涉及在变形时使用显微镜和样品的XCT。这提供了导致微结构尺度断裂的过程的详细历史，包括多相材料中相之间的负载转移。 AHSS代表了一类合金，它们结合了高强度和延展性，使其对汽车应用有吸引力。但是，很少对限制延展性的机制进行研究，其中大多数专注于拉伸伸长而不是真正的故障菌株。这至关重要，因为前者解释了某些过程（例如拉伸形成）的限制，但真正的故障菌株与弯曲失败有关。我的小组开发了微观数字图像相关方法来解决此问题。现在，我们有能力将其应用于第三代钢，这对于燃油有效的车辆开发至关重要。多相HEAS是一类新的微型复合材料，它们结合了两种高熵合金 - 一种具有高延展性，另一个具有高强度。这些材料直到最近才开发。因此，对控制其延展性的机制没有理解。我们需要了解相规和分布如何影响变形过程中的损伤积累。这项研究将使我们能够开发最佳的微观结构，以将裂缝延迟到高应变。