Effects of Cr Content on Microstructure and Mechanical Properties of WMoNbTiCr High-Entropy Alloys

Refractory high-entropy alloys (HEAs) are promising structure materials in elevated temperature. In the present studies, refractory WMoNbTiCr HEAs with different Cr content were prepared by mechanical alloying followed spark plasma sintering. The effects of chromium content on microstructure and room temperature mechanical properties of WMoNbTiCr HEAs were investigated. The results showed that there are three body-centered cubic (BCC) solid solution phases in the ball-milled powders, including enriching with W, Nb, and Cr solid solution phases, respectively. The bulk WMoNbTiCr alloys were mainly composed of disordered BCC phases and a small amount of Laves phase. As the content of Cr increased from 5 to 20 at.%, the relative content of Laves phase increased correspondingly. With an increase in Cr content, the hardness, fracture toughness, compressive fracture strength, and compressive strain of the WMoNbTiCr HEAs increased, exhibiting the maximum values of 9.73 GPa, 6.68 MPa m(1/2), 2116 MPa, and 5.1%, respectively. With an addition of 20 at.% Cr, the WMoNbTiCr HEA exhibited a more refined microstructure. The increasing fracture toughness and compressive strain were mainly attributed to the grain refinement. However, the solid solution strengthening, the second-phase (Laves phase) strengthening, and microstructure refinement resulted in an increase in the hardness and compressive fracture strength.