Improvement of metallurgical properties of A356 aluminium alloy by AlCrFeSrTiBSi master alloy

Abstract

A new AlCrFeSrTiBSi master alloy was manufactured by in situ synthesis in Al melt, and compared with AlBSr master alloy. Microstructures of A356 alloy modified with AlCrFeSrTiBSi master alloy were investigated, and the structural details of the new cast A356 alloy were evaluated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness and differential thermal analysis (DTA). AlBSr master alloy typically formed α-Al and granular SrB6 phases in A356, and the samples inoculated with AlCrFeSrTiBSi master alloy consisted of additionally AlCrFeSi phase with irregular blocks. The addition of 0.1 wt%AlCrFeSrTiBSi alloy to the A356 alloy significantly refined and modified the grain structure together. The structure of eutectic Si converted from acicular form to fibrous. The size of α-Al dendrites declined from ∼1000 μm to ∼100 μm. The strength values of the A356 alloy were developed by ∼70% with the addition of 0.1 wt%AlCrFeSrTiBSi master alloy.