Carbides in Ti-45Al-5Nb Alloys with Different Carbon Contents

摘要

The mechanical properties of γ-TiAl based alloys are often improved through alloying with niobium and carbon. Depending on chemistry and heat treatment the details of carbon distribution and the resulting consequences on mechanical properties vary greatly,which is discussed controversially in literature. Here we present a study of the microstructure of Ti-45Al-5Nb alloys (in at.-%) with the addition of 0. 5-1 at.-% of carbon,produced from powders through hot iso-static pressing at 1250°C for 2h at 200 MPa. We use electron diffraction accompanied by energy dispersive spectroscopy to characterize particles embedded in the Ti-Al matrix. These studies are complemented by high-energy x-ray diffraction experiments using synchrotron radiation that scan a larger specimen volume and by scanning electron microscopy. Carbides are identified in significant numbers in the alloy containing 1 at.-% of carbon but only rarely at 0. 5 at.-% C. Our results show that in this alloy series carbon in solid solution affects the hardness stronger than carbide precipitation.