Structural characterization of a composite joint prepared during laser welding of Ti–22Al–27Nb intermetallic alloy with an interlayer of Cu-Hf-Ni-Ti-Zr high entropy bulk metallic glass

Abstract

The advent of high entropy alloys (HEAs) has provided scientific solutions to material related problems of grave importance. High-temperature embrittlement (HTE) in the laser welded joint (LWJ) of titanium aluminides is one of the challenges, known to impede the prevalent applications of this novel alloy system. In the current research work, a sandwich-structured composite joint of an intermetallic based alloy (Ti–22Al–27Nb) with a high entropy bulk metallic glass (HE-BMG) composed of Cu, Hf, Ni, Ti and Zr was welded through laser beam. The adulteration of LWJ with HE-BMG resulted into evolution of finite microregions in the fusion zone (FZ) through heterogeneous nucleation. The FZ comprised fine-grained B2 phase with greater fractions of high angle grain boundaries (HAGBs) and lower degree of local area misorientations (LAM). The crystal texture of B2 phase in the FZ abetted the plastic deformation at room as well as high temperature (650 °C), as the Schmid factor “m” for ≥ 99% of {1 1 0} <1 1 1> slip system of B2 remained greater than 0.38. The high-resolution transmission electron microscopy revealed the presence of nano-sized composite regions (NCRs), composed of crystalline/non-crystalline structure. These NCRs remained stable at 650 °C and inhibited the nucleation of O phase along B2 grain boundaries (GBs). The percentage elongation of HE-BMG supplemented LWJ of Ti–22Al–27Nb was improved by 28.19 and 31.34% at room temperature and 650 °C, respectively. The dilution of FZ with HE-BMG contributed a significant increase in tensile ductility at room as well as high temperature.