The Grain Boundary Wetting Phenomena in the Ti-Containing High-Entropy Alloys: A Review

Abstract

In this review, the phenomenon of grain boundary (GB) wetting by melt is analyzed for multicomponent alloys without principal components (also called high-entropy alloys or HEAs) containing titanium. GB wetting can be complete or partial. In the former case, the liquid phase forms the continuous layers between solid grains and completely separates them. In the latter case of partial GB wetting, the melt forms the chain of droplets in GBs, with certain non-zero contact angles. The GB wetting phenomenon can be observed in HEAs produced by all solidification-based technologies. GB leads to the appearance of novel GB tie lines Twmin and Twmax in the multicomponent HEA phase diagrams. The so-called grain-boundary engineering of HEAs permits the use of GB wetting to improve the HEAs’ properties or, alternatively, its exclusion if the GB layers of a second phase are detrimental.

Influence of Molybdenum on the Microstructure, Mechanical Properties and Corrosion Resistance of Ti20Ta20Nb20(ZrHf)20−xMox (Where: x = 0, 5, 10, 15, 20) High Entropy Alloys

“…As can be seen in Figure 4 , the interdimeric BCC2 phase separates from each other dendritic grains of the BCC1 phase. Based on the grain boundary wetting theory described by J. W. Cahn [ 60 ] and further studied by Straumal et al [ 61 , 62 , 63 ] such observation indicates that during the solidification process the molten metal completely separates the majority of BCC1 primary grains from each other. Grain boundaries of BCC1 phase were completely wetted by the mold.…”

High Entropy Alloys Coatings Deposited by Laser Cladding: A Review of Grain Boundary Wetting Phenomena

“…It is described for many binary alloys. In this case the contact angle θ usually decreases with growing temperature and can reach zero at a certain temperature, T w [46,[48][49][50]. At T w the incomplete GB wetting changes to the complete one.…”

“…The GB wetting phase-transition can be of the first or second order as for conventional bulk phase transformations [51][52][53]. If the GB wetting transformation is of a first-order, then the first derivative of θ, with respect to temperature, dθ/dT has a discontinuity at T w [46,51,52]. In this case, exhibits dθ/dT drops suddenly from a certain finite value to 0 [46,51,52].…”

“…If the GB wetting transformation is of a first-order, then the first derivative of θ, with respect to temperature, dθ/dT has a discontinuity at T w [46,51,52]. In this case, exhibits dθ/dT drops suddenly from a certain finite value to 0 [46,51,52]. If the GB wetting phase transition is continuous (or of a second-order), then dθ/dT continuously decreases with increasing T and reaches zero dθ/dT = 0 at T w [51,52].…”

The effect of zirconium on the Ti-(42-46 at.%)Al system

“…The current work presents a detailed investigation of the effect of Zr in six model alloys with systematically varied compositions based on the Ti- (42)(43)(44)(45)(46)Al-(2-4)Zr (at.%) system. The influence of Zr on the microstructure of the materials is shown, while differential scanning calorimetry (DSC) is employed to study the phase transformation behaviour.…”