The Effects of the Al and Zr Contents on the Microstructure Evolution of Light-Weight Al_xNbTiVZr_y High Entropy Alloy

To investigate the comprehensive effects of the Al and Zr element contents on the microstructure evolution of the AlNbTiVZr series light-weight refractory high entropy alloys (HEAs), five samples were studied. Samples with different compositions were designated Al_1.5NbTiVZr, Al_1.5NbTiVZr_0.5, AlNbTiVZr, AlNbTiVZr_0.5, and Al_0.5NbTiVZr_0.5. The results demonstrated that the actual density of the studied HEA samples ranged from 5.291 to 5.826 g·cm^-3. The microstructure of these HEAs contains a solid solution phase with a BCC structure and a Laves phase. The Laves phase was further identified as the ZrAlV intermetallic compound by TEM observations. The microstructure of the AlNbTiVZr series HEAs was affected by both the Al and Zr element contents, whereas the Zr element showed a more dominant effect due to Zr atoms occupying the core position of the ZrAlV Laves phase (C14 structure). Therefore, the as-cast Al_0.5NbTiVZr_0.5 sample exhibits the best room temperature compression property with a compression strength (σ_p) of 1783 MPa and an engineering strain of 28.8% due to having the lowest ZrAlV intermetallic compound area fraction (0.7%), as characterized by the EBSD technique.