Revealing the solidification microstructure evolution and strengthening mechanisms of additive-manufactured W-FeCrCoNi alloy: Experiment and simulation

Tungsten heavy alloys (WHAs) prepared using laser additive manufacturing (AM) exhibit intricate geometries, albeit with limited mechanical properties. Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy (HEA) binder via the laser metal deposition (LMD) technique. Due to the distinctive thermal cycle and rapid cooling rate, the as-deposited alloys exhibit microstructures with hypoeutectic, eutectic-like, and spot-like characteristics. To elucidate this phenomenon, the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilibrium simulation. The μ phase precipitated out from the supersaturated solid solution, thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate. Furthermore, the μ phase formed an ultrafine intermetallic compound (IMC) layer around the W grain, reducing the hole or crack between the W grain and FeCrCoNi matrix. Attributed to the precipitation strengthening, the solid solution of the FeCrCoNi binder, along with the load-bearing strength of W, the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32% respectively at room temperature. These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys, leveraging their excellent properties.