Microstructure and Mechanical Properties of NiAlCrFeMo High-Entropy Alloy Sheet under Different Hot-Rolling Parameters

This study investigates the hot rolling of a newly developed NiAlCrFeMo high-entropy alloy, which demonstrates excellent high-temperature mechanical properties but is prone to cracking due to its unique microstructure. Hot-rolling experiments were conducted with varying rolling temperatures (1000-1100 °C), rolling speeds (300-900 r/min), and reduction amounts (5-20%) using a double-stick hot- and cold-rolling mill. Results show that as the reduction amount increases, the grain size refines, and the alloy's mechanical properties are optimized at a 20% reduction, with tensile strength increasing by 40.6% (966.1 MPa) and elongation by 14.8% (3.1%) compared to the cast state. At a 5% reduction, the FCC phase volume fraction is highest (66%), leading to the best ductility due to maximum crystal randomness. As rolling speed increases, grain size decreases, and the FCC phase volume fraction increases. At 900 r/min, tensile strength improves by 26.1% (866.5 MPa) compared to the cast state. The increase in rolling temperature leads to larger grain sizes, and at 1100 °C, a reverse phase transformation occurs, increasing the BCC phase volume fraction. Compared with the as-cast state, the specimen that has undergone 1000 °C rolling treatment exhibits significantly enhanced tensile strength and elongation in the subsequent room-temperature tensile test, with the tensile strength increasing by 13.5% to 779.8 MPa, and the elongation increasing by 11.1 to 3%.