# Novel Al-Ce-C-O-Mg Grain Refiners with Superior Efficiency and Mechanical Properties Enhancement for AZ91 Alloys

## TL;DR

A new grain refiner improves the structure and strength of AZ91 magnesium alloys by reducing grain size and enhancing mechanical properties.

## Contribution

A novel Al-Ce-C-O-Mg grain refiner was developed using a rolling-assisted process, achieving significant grain refinement and mechanical property enhancement in AZ91 alloys.

## Key findings

- Adding 1.0 wt.% of the grain refiner reduced AZ91 alloy grain size by 73%.
- The refiner transformed coarse β-Mg17Al12 phases into a more uniform distribution.
- Mechanical properties like tensile strength and elongation improved significantly.

## Abstract

Grain refinement represents a critical approach in optimizing the as-cast microstructure of magnesium alloys, playing a pivotal role in the development of high-performance magnesium alloys. In the present research, a novel Al-Ce-C-O-Mg grain refiner was fabricated using an innovative rolling-assisted process, and the influence of the grain refiner on the grain size evolution of as-cast AZ91 alloy was systematically examined. The Al-Ce-C-O-Mg grain refiner prepared by the rolling-assisted process contains two types of effective refining particles—MgAl2O4 and Al4C3. These particles can act as potent nucleation sites for α-Mg in the melt, promoting efficient nucleation and achieving significant grain refinement. By adding 1.0 wt.% of the Al-Ce-C-O-Mg grain refiner to the AZ91 alloy, the grain size of the original AZ91 alloy was reduced by 73%. Moreover, adding a refiner facilitated the transformation of the coarse β-Mg17Al12 phase morphologies into a more uniformly distributed and dispersed form. The addition of 1.0 wt.% Al-Ce-C-O-Mg grain refiner to the AZ91 alloy resulted in significant improvements in its mechanical properties. The ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) increased from 158 MPa, 104 MPa, and 3.9% to 203 MPa, 121 MPa, and 6.3%, respectively. The grain refiner developed in this study demonstrates promising potential for application in Mg alloys.