In situ CrB2 and its effect on the mechanical properties of A390 alloy

In this work, a series of CrB2/A390 composite alloys have been prepared and analyzed by a field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Firstly, in situ CrB2 has been prepared by reducing reaction that occurred in Al melt: AlB2 + [Cr] → Al + CrB2. The CrB2 particles exhibit regular hexagonal platelet morphology and distribute uniformly in the Al matrix. Then, A390 alloys with different CrB2 additions have been prepared. With the addition of CrB2, the size of primary Si can be reduced remarkably. The generation of CrB2 particles and their diffuse distribution can improve the mechanical properties of A390 alloy obviously. The mechanical properties of the base alloy, including ultimate tensile strength at 25 °C (UTS25 °C), the coefficient of thermal expansion (CTE) and wear resistance have been studied and the composite alloy with 3 wt.% CrB2 particle addition showed the best performance.