Effect of Rare-earth Element Addition on Structure of Heat-resistant Ti–6.5Al–4Zr–2.5Sn–2.4V–1Nb–0.5Mo–0.2Si Titanium Alloy

Abstract

To guarantee the requirements for modern technology it is necessary to create new alloys with enhanced characteristics or upgrade existing ones. Especially it concerns high-tech industries, particularly aviation and rocket engineering. When designing and creating modern aircraft engines, a special place is devoted to heat-resistant titanium alloys. High strength characteristics and relatively low density make it possible to create alloys with outstanding specific parameters. However creation of new alloying systems is quite expensive and implies parallel development of technological process as well as various processing modes. There are several ways to solve this problem; one of them is modification of already existing alloy. Due to the unique combination of physical-chemical properties of rare earth metals adding them to existing alloying systems makes it possible to create alloys with increased characteristics. In particular, microalloying of titanium alloys with gadolinium leads to transformation of their microstructure and increase of some mechanical characteristics. Thus, microalloying of the high-temperature Ti–6.5Al–4Zr–2.5Sn–2.4V–1Nb–0.5Mo–0.2Si titanium alloy in as-cast state results in a change in the intragranular structure, but does not significantly affect the macrostructure of the ingots. At the same time, in deformed state increase of gadolinium content leads to refinement of the initial β-grain, growth and formation rates of the primary and secondary phases change, which in its turn affects the mechanical characteristics of the alloying system as a whole. The Rockwell hardness measurements carried out using the BUEHLER Macromet 5100T device show an increase of parameters in the alloy with gadolinium.