Microstructure and Mechanical Properties of TiB-Containing Al-Zn Binary Alloys

The microstructure and mechanical properties of newly developed Al-35Zn cast alloys with TiB refiner addition were evaluated by X-ray diffractometry, optical microscopy, and scanning electron microscopy coupled with energy dispersive spectrometry. The microstructure of these alloys featured α-Al dendrites surrounded by Al-Zn (α + η) eutectic structures. After the addition of TiB refiner, the alloy grain sizes decreased, and its morphology abruptly changed from dendritic to equiaxed grains. Such an improved microstructure of the modified alloys was accompanied by a significant increase in the tensile strength and elongation percentage compared to those of the Al-Zn or Zn-Al-based alloys. The results showed that with the increase of TiB content up to 0.05%, the morphology of α-Al dendrites and α + η phases changed from coarse dendrite and lamellar structures into independent and fine ones. Based on these results, the effect of TiB refiner addition on the microstructure and mechanical properties of the Al-35Zn binary alloys was investigated.