Microstructure/properties relationship of advanced heat-resistant intermetallics tial(Nb,Cr,Zr) after casting and float zone processing

Abstract

New Ti-44Al-5Nb-3Cr-1.5Zr (at.%) β-stabilized intermetallic alloy was synthesized by the electron beam casting and afterwards re-solidified by the high-gradient (300 °C cm−1) induction float zone (FZ) technique. FZ-processing led to the ordered microstructure creation consisting of volumetrically prevailing (γ + α2) lamellar colonies separated by minor seam-like γ-granular interlayers, and the least intergranular quota of β(Ti)/B2 phase. The optimum phase balance, submicron interlamellar spacing and preferable alignment of lamellae along the thermal gradient were controlled by FZ-conditions. Unique microstructural adjustment enhances drastically the high-temperature yield strength, Young modulus and creep resistance. Thus the thermal limit of γ-TiAl(Nb,Cr,Zr) structural applicability could be extended from 750–800 °C towards 900–950 °C.