Grain Refinement of Mg-Al Alloys by a New Al-4.1V-1.7B Refiner Containing Sole VB2 Particles

Grain refinement is a promising way to improve strength and ductility simultaneously in a given metallic material. In this study, a new grain refiner Al-4.1V-1.7B containing sole VB2 particles is prepared by the liquid solidification reaction method. The grain refiner is added to the Mg-Al alloy to evaluate the refining ability. The results indicate that the Al-4.1V-1.7B grain refiner exhibits a remarkable refinement effect on Mg-Al alloys. High-resolution transmission electron microscope (HRTEM) examination and edge-to-edge models (E2EM) were utilized to explore the refining mechanism. The results revealed that there are well-defined crystallographic orientation relationships between VB2 and alpha-Mg matrix: [1 (2) over bar 10](VB2)/[1 (2) over bar 10](alpha-Mg) in (10 (2) over bar0)(VB2)/(0002)(alpha-Mg), which indicated the VB2 particles can play the role of nucleation sites for alpha-Mg during solidification, resulting in a good grain refining effect. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of AZ31 alloy were significantly increased from 153 MPa, 68 MPa and 9.6% to 207 MPa, 89 MPa and 16.7%, respectively, with 1.0 wt.% Al-4.1V-1.7B grain refiner addition.