Full Length Article Stabilization of Al3Zr allotropes in dilute aluminum alloys via the addition of ternary elements

The formation of Al3Zr particles within dilute aluminum alloys can contribute effectively to controlling microstructure evolution and enhancing material properties. However, the possible transformation of Al3Zr from its initial metastable crystal structure L1(2) into its stable, tetragonal structure D0 (23) is associated with faster coherency loss and the coarsening of Al3Zr particles. In this regard, our study aims at identifying ternary elements that can disrupt this mechanism. For this purpose, nine ternary Al-Zr-X alloys (Er, Sc, Hf, Y, Nb, Mn, Cu, Zn and Si) plus a base alloy (Al-Zr) were produced. Isochronal aging was performed at 475 degrees C and 550 degrees C, and an investigation of the particle landscape was carried out by STEM and HR-TEM. In parallel, we conducted ab initio calculations to investigate fundamental properties of ternary AlZrX-particles such as substitution likeliness, heat of formation and transformation mechanisms. The elements investigated show various behaviors. Fewer than half of the elements (Er, Sc, Hf and Si) are found to be incorporated into Zr-rich particles to any large extent; Er and Sc exhibit the well-known core-shell structure. Y and Zn do not interfere at all with the precipitation process. Nb, Mn and Cu form particles on their own, with Zr particles often attached to them. Concerning crystal structures, all element additions except for Y and Si widen the stability regime of L1(2) .

Automated summary

The formation of Al3Zr particles in dilute aluminum alloys is important for controlling microstructure evolution and enhancing material properties. In this study, nine ternary Al-Zr-X alloys were produced to identify elements that can disrupt the transformation of Al3Zr particles. Experimental and computational analyses were conducted to investigate the behavior and impact of different elements.