Titanium alloy design and casting process development using an Integrated Computational Materials Engineering (ICME) approach

¹ Department of Materials Science & Engineering, The Ohio State University, Columbus, OH 43210, USA
² Now at National Institute of Standards & Technology, Gaithersburg, MD 20878, USA
³ Global Research and Development, General Motors, Warren, MI 48090, USA
⁴ Department of Integrated Systems Engineering, The Ohio State University, Columbus, OH 43210, USA
⁵ Department of Materials Science & Engineering, University of North Texas, Denton, TX 76203, USA

Abstract

The application of titanium components is generally limited by their high raw material and manufacturing costs. In this paper, a lower cost cast titanium alloy based on the Ti-Al-Fe system has been designed using an ICME approach. The new alloy Ti-6Al-5Fe-0.05B-0.05C (all wt.%) significantly reduces raw material cost and demonstrates improved castability compared with the baseline Ti-6Al-4V alloy. The fine primary and secondary α phase microstructure in the new alloy, due to Fe partitioning, provides exceptionally high strength (1023 MPa yield strength and 1136 MPa ultimate tensile strength) and reasonable ductility (3.7% elongation) for structural applications. On the manufacturing front, the high cost multi-step investment casting process currently used can now be replaced with a low-cost permanent mold casting process using steel molds and a novel ceramic coating. An experimental casting setup, including an induction skull melting (ISM) system, a gravity tilt-pour system and a ceramic-coated H13 steel mold, has been used to produce near-net-shape permanent metallic mold castings with the new titanium alloy developed. Using this setup, and aided by casting process simulation, a prototype automotive connecting rod was cast successfully. The ZrO2 ceramic coating applied to the H13 steel mold was proven effective in minimizing the metal-mold reactions.