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.
