Effect of Mo, Ta, V and Zr on a duplex bcc+orthorhombic refractory complex concentrated alloy using diffusion couples

Abstract

A scanning method based on diffusion couples has been set up to experimentally explore phase diagrams and to observe the stable phases in quinary alloys. This method enables to realize a fast, experimental and reliable scanning of composition and then determine promising alloy compositions for potential structural application. Aiming at developing promising refractory complex concentrated alloys (RCCAs), the method was applied on the Ti-Nb-Al-Si system with an initial two phase, body-centered cubic (bcc) + orthorhombic (O), microstructure and focuses on the effect of Mo, Ta, V and Zr additions on this microstructure. The evolution of the orthorhombic phase fraction according to the content of additional elements was quantified, as well as the maximum concentration of those elements in order to stabilize the duplex microstructure, and maintain it above 800 • C. In such framework, it appears that Mo, Ta and V show the most promising effects on the Ti-Nb-Al-Si system. The comparisons between experimental results and calculated phase diagrams using current thermodynamic database showed that these calculations applied to RCCAs are good qualitative tools but are not accurate enough to be used as predictive means.

Aging behavior of two refractory Ti-Nb-(Hf, Zr)-Al high entropy alloys

“…Note that the particles in the recrystallized conditions can be formed during cooling after annealing as no specific attention was paid to ensure fast cooling rates. The CALPHAD method thus confirms the negative influence of Zr on the O-phase stabilization, which is also in agreement with some recent results [43]. The effect of Zr can be associated with a highly negative enthalpy of the Zr aluminides formation [48], making their appearance preferable over the Ti 2 AlNb-based O-phase.…”

“…Therefore, there is an interest in other approaches to develop precipitation-strengthened RHEAs. Recently, several new RHEAs with an orthorhombic (O) phase embedded in the bcc matrix were introduced [42,43]. For example, in a Ti 40 Nb 30 Hf 15 Al 15 alloy [42], the O-phase increased strength with a slight decrease in plasticity.…”

Interdiffusion in refractory metal systems with a BCC lattice: titanium–tantalum and titanium–multicomponent (high-entropy) alloy

“…Из 47 отобранных статей первому критерию удовлетворяли только 10 работ [5][6][7][8][9][10][11][12][13][14], а изучению проблем диффузии в ВЭС тугоплавких металлов с ОЦК-решеткой -лишь 3 [6,9,11]. Исследований диффузии в многокомпонентных ВЭС с ГЦК-решеткой значительно больше, чем с ОЦК.…”