Lightweight and high hardness (AlNbTiVCr)100-Ni high entropy alloys reinforced by Laves phase

Tailoring the phase constituents by alloying is an available exploration route to improve the integrated mechanical properties. (AlNbTiVCr)100-xNix (x = 0, 0.5, 1, 1.5, and 2, at.%, simplify as Ni0, Ni0.5, Ni1, Ni1.5, and Ni2 alloy, respectively) high entropy alloys were designed and prepared. The effect of Ni on phase formation, microstructure and mechanical properties is evaluated. The addition of Ni transforms the alloys microstructure from a single BCC phase to a mixture of BCC phase, C14 Laves phase and C15 Laves phase. The doping of Ni promotes precipitation of Nb and Cr, resulting in atomic size mismatch and shear modulus mismatch caused by Nb and Cr, respectively. The volume fraction of the Laves phase gradually increases. In room temperature compression test, Ni1.5 alloy exhibits a better combination of compressive strength of 1906.2 MPa, fracture strain of 15.2%, and high specific strength of 330.9 MPa/g × cm−3. When Ni content is 2 at. %, Vickers hardness reaches the maximum value of 740.8 HV. An improvement in compressive strength and Vickers hardness is due to solid solution strengthening and precipitated phase strengthening. This study provides important experience for the design and preparation of lightweight structural materials for practical applications.