Evaluation of high-temperature formability for Ti-xMo-4Fe metastable beta alloys based on Mo contents

Abstract

High-temperature formation technology is widely used to fabricate components with metastable β titanium alloys, a material characterized by balanced mechanical properties, including superb formability, corrosion resistance, and high strength. In high-temperature formation, it is crucial to control the formation conditions by linking the changes in those conditions caused by processing variables with microstructures and identifying the optimal conditions for high-temperature formation. As such, in this study, a Ti–Mo–Fe alloy was designed that is different from conventional metastable β titanium by adding molybdenum (Mo) and iron (Fe), which are relatively economical β stabilization elements. The mechanical characteristics of the alloy at room temperature were also examined by varying the Mo content, and a high-temperature compression test was conducted to evaluate its high-temperature characteristics and formability. The high-temperature compression test was performed at five different temperatures (700 °C, 750 °C, 820 °C, 900 °C, and 950 °C) to avoid β-transus and with four different strain rates 1 × 10−3/sec, 1 × 10−2/sec, 1 × 10−1/sec, and 1 × 100/sec. Then, the test results were utilized to create a processing map, which evaluated formability by examining plastic instability and energy distribution efficiency at different temperatures, strain rates, and reduction rates, the processing variables for high-temperature formation. Afterward, their connections with the microstructures were analyzed to determine the optimal conditions for the temperature formation of the newly designed Ti–Mo–Fe metastable β titanium alloy.