Low-Cost Titanium Casting Technology

Abstract

This is the final report of "Low-Cost Titanium Casting Technology" project. Titanium alloys have attracted increasing attentions as structural materials for high performance and weight-sensitive applications in aerospace and biomedical fields. However, in mass-production of civil applications like automotive components, titanium alloys are scarcely used due to the unaffordable costs in manufacturing compared with other metallic materials, such as aluminum, magnesium and steel. Therefore, there is a need to reduce the manufacturing cost of titanium alloys so that titanium alloys can be more competitive in terms of property and cost considerations. In this 4-year project, we started from exploring new low-cost titanium alloy systems with the guidance of Integrated Computational Materials Engineering – Calculation of Phase Diagram (ICME-CALPHAD) framework, and determined several promising alloy systems, alloying elements including Ti-Al-Fe-Mn-B-C, that can allow further development (lab-scale and industry-scale) in the future. During the new alloy system exploration, considerable amount of scientific work was completed regarding CALPHAD modeling, microstructure morphology, mechanical properties, and processing of the new alloy systems. The relevant ternary titanium alloy systems, Ti-Al-Mn and Ti-Al-Fe, were examined and reassessed both computationally and experimentally, leading to more comprehensive understanding of these alloy systems. Based on this above study, a new low-cost casting titanium alloy was developed, Ti-6Al-5Fe-0.05B-0.05C (designated as T65-0.05BC), which has competitive as-cast strength level with current commercial titanium alloys but relatively low ductility. However, in this project, since the target application, automotive engine connecting rod, is a fatigue-limited component and does not require high ductility, this alloy shall suffice as the deliverable alloy in this project. After designing and confirming the potent of the new alloy, we designed and built a lab-scale manufacturing equipment aided by computational tools at OSU labs to conceptually prove that this alloy can be manufactured with permanent mold casting, which is low-cost and potentially a mass production process. We produced a lab-scale prototype connecting rod demonstrating the capability of permanent mold casting of this new alloy.