Microstructural Impact on the Machinability of Titanium Alloys

钛合金具有轻质和高强度的优良组合，因此在许多工程应用中都是可取的。在最终生产之前，大多数钛零件必须经过机械加工过程，这往往是困难和昂贵的。钛零件和机床的损坏都很常见，关于是什么导致了这种损坏，以及如何控制它，人们知之甚少。该奖项支持基础研究，以研究钛合金零件加工过程中的变形和磨损机理。合金的超细尺度结构对于确定钛加工中刀具磨损、切割行为和分段切屑的根本原因具有重要的关键作用，了解这种结构和加工之间的基本关系将使研究人员建立必要的知识，以确定刀具设计策略，优化合金结构以实现更好的加工性，并预测部件的性能。这一新知识将在许多制造业中具有广泛的适用性，包括航空航天、汽车和基础设施。此外，这一奖项还将带来巨大的教育收益，包括为学生提供各种最先进的研究项目的机会和经验。这个跨学科团队将把机械工程和材料科学的研究人员聚集在一起，对钛合金微观结构的差异如何影响可加工性指标建立基本的理解。钛合金的显微组织非常复杂，大多数合金(包括最常用的商业合金Ti-6Al-4V)都有两种截然不同的相：各向异性的六方密排(HCP)相和更各向同性的体心立方(BCC)相。作为先前成形和热处理工艺的结果，这两个相在各种形态和织构中的许多组合是可能的。这项工作将调查加工前的微观结构如何影响可加工性指标，如切屑分割、刀具磨损、过程动力学和成品的表面完整性。这项工作的目标是确定和量化钛组织和这些可加工性指标之间的相互作用。成功的结果将为刀具和切割参数的选择提供科学的见解和理论基础，这些刀具和切割参数根据合金的微观结构和成分进行调整，并产生具有高度结构完整性的机械加工部件。这一新知识将导致能够描述和预测许多观察到的现象，如刀具上的微切屑、分段切屑和在高速切割时刀具过度磨损。这将导致合理的方法，通过优化材料规格的可加工性和产品性能，以及确定改进的方法来加工钛合金，从而降低整体加工成本。

Titanium alloys have an excellent combination of light weight and high strength, and thus are desirable for a number of engineering applications. Before final production, most titanium parts must undergo a machining process, which is often difficult and costly. Damage to both the titanium part and the machine tool are common, and little is known about what leads to this damage or how it can be controlled. This award supports fundamental research to investigate the mechanisms of deformation and wear during the process of machining titanium alloy parts. The very fine-scale structure of the alloys holds important keys to identify the root causes of tool wear, cutting behavior, and segmented chips in titanium machining, and understanding the fundamental relationships between this structure and processing will allow researchers to build the knowledge needed to to identify cutting tool design strategies and to optimize the alloy structure for better machinability, and predict the performance of a component. This new knowledge will have broad applicability in a number of manufacturing industries, including aerospace, automotive, and infrastructure. Additionally, strong educational benefits will result from this award, including diverse opportunities and experience for students in state-of-the-art research programs.This interdisciplinary team will bring researchers from Mechanical Engineering and Materials Science together to develop a fundamental understanding of how differences in the microstructure of titanium alloys affect machinability metrics. The microstructure of titanium alloys is quite complex, and most alloys (including the most common commercially used alloy, Ti-6Al-4V) have two distinct phases: an anisotropic hexagonal close-packed (HCP) phase, and a more isotropic body-centered cubic (BCC) phase. As a result of prior forming and heat treatment processes, many combinations of the two phases in various morphologies and textures are possible. This work will investigate how the microstructure prior to machining affects machinability metrics such as chip segmentation, tool wear, process dynamics, and the surface integrity of a finished product. The objective of this work is to identify and quantify the interplay between the titanium microstructure and these machinability metrics. A successful outcome will lead to science-based insights and rationale for choices of tools and cutting parameters that are tuned to the microstructure and composition of an alloy, and result in machined components with high structural integrity. This new knowledge will lead to the ability to describe and anticipate many observed phenomena such as micro-chipping on cutting tools, segmented chips and excessive tool wear at high cutting speeds. This will lead to rational approaches to reduce the overall processing cost by optimizing material specifications for machinability and product performance, as well as identifying improved ways to machine titanium alloys.