Microstructure, Thermal and Mechanical Properties of Novel Nanocrystalline Al-B-Si Alloy

In this study, a nanostructured Al50B45Si5 alloy was produced by the mechanical alloying technique from mixtures of high-purity Al, B, and Si powders. The thermal behavior, structural evolution, and mechanical properties of the powders were examined through X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), differential scanning calorimetry (DSC), differential thermal analysis (DTA), transmission electron microscopy (TEM), and Vickers microhardness measurements. The XRD results revealed that all crystalline peaks belonging to the Al, B, and Si elements disappeared during mechanical alloying and were eventually replaced by peaks from intermetallic phases such as AlB2, B4Si, and AlB12 in the supersaturated Al(Si) matrix. The crystalline size of the Al50B45Si5 alloy was calculated by the Debye Scherrer equation, and it was determined to be 9.5 nm, consistent with TEM measurements. The microhardness value of the alloy was 219±10 HV, while the hardness increased to 345±9 HV with heat treatment. Therefore, a nanostructured Al50B45Si5 alloy with high hardness, good thermal stability, and homogeneity was favorably synthesized by mechanical alloying for use in industrial applications.