Influence of Cooling Rate and Aging on the Lamellar Microstructure and Fractography of TC21 Titanium Alloy

Abstract

A new titanium alloy (Ti-5. 97Al-2. 06Sn-2. 02Zr-2. 96Mo-1. 25Cr-2. 08Nb-xSi, wt.%) was cooled at different rates to produce a variety of microstructures. Phase and microstructure characterization were performed using LM, SEM, TEM, and XRD. The β phase transformed to the α″ phase upon water quenching. The transformation (β → βmetastable + α) took place when the cooling rate decreased to the air cooling and furnace cooling rates. After a subsequent aging treatment, both the α″ and the metastable β phase decomposed into α and β phases with different morphologies. The tensile and yield strength values depended on the final microstructures and were related to the fractal dimension of the fracture surfaces. © 2013 Springer Science+Business Media New York and ASM International.