Laser Beam Welding of a Low Density Refractory High Entropy Alloy

Abstract

The effect of laser beam welding on the structure and properties of a Ti1.89NbCrV0.56 refractory high entropy alloy was studied. In particular, the effect of different pre-heating temperatures was examined. Due to the low ductility of the material, laser beam welding at room temperature resulted in the formations of hot cracks. Sound butt joints without cracks were produced using pre-heating to T ≥ 600 °C. In the initial as-cast condition, the alloy consisted of coarse bcc grains with a small amount of lens-shaped C15 Laves phase particles. A columnar microstructure was formed in the welds; the thickness of the grains increased with the temperature of pre-heating before welding. The Laves phase particles were formed in the seams after welding at 600 °C or 800 °C, however, these particles were not observed after welding at room temperature or at 400 °C. Soaking at elevated temperatures did not change the microstructure of the base material considerably, however, “additional” small Laves particles formed at 600 °C or 800 °C. Tensile test of welded specimens performed at 750 °C resulted in the fracture of the base material because of the higher hardness of the welds. The latter can be associated with the bcc grains refinement in the seams.

A Review of the Latest Developments in the Field of Refractory High-Entropy Alloys

“…To overcome the hot cracking problem, preheating was carried out between 600 and 800 • C. This provided sound butt joint welds. As the preheating temperature increased, the grain size increased, as shown in Figure 4 [57].…”

Welding of high-entropy alloys and compositionally complex alloys—an overview

“…There are further studies on welding of HEAs/CCAs by special processes such as explosion welding [35], diffusion welding [36], and individual examinations on refractory HEAs [37]. These investigations will not be discussed in the following, as this overview focuses on basic welding properties of the equiatomic CoCrFeMnNi HEA ("Cantor" alloy in accordance with [6]) and various compositions of the Al x CoCrCu y FeNi (with 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1) HEAs/ CCAs [38][39][40].…”

A Short Review on Welding and Joining of High Entropy Alloys

“…Several studies [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] have already been reported on fusion-based welding of HEAs. To date, these works focus mainly on laser-based techniques, although some information is also available on Electron Beam and Gas Tungsten Arc Welding (GTAW) techniques.…”

“…Panina et al [69] reported the effects of pre-heating temperature (400, 600, and 800 • C) on the laser weldability of a Ti 1.89 NbCrV 0.56 refractory high entropy alloy. Initially, the BM microstructure was mainly composed by BCC grains presenting also small C15 Laves phase particles.…”