Diffusion and Phase Formation at Matrix-Filler Interfaces in Al–Mg–Si Composites Prepared by Powder Metallurgy

Abstract: The Al–Mg–Si composites employing aluminum (Al) as matrix, magnesium (Mg) and silicon (Si) as fillers with weight ratio of 60 : 20 : 20 have been prepared by the method of powder metallurgy. The mixed powders were pressed applying pressure of 700 MPa, followed by sintering at 500, 550, and 600°C for 3 h in inert atmosphere. The resulted samples have been studied using a scanning electron microscope (SEM), equipped with energy dispersive X-ray (EDX) and electron probe micro analyzer (EPMA). Experimental results showed that the distribution of Mg and Si were homogeneous in the Al matrix. According to the elemental mapping and diffusion equation under non-steady state condition, the atomic interdiffusion process at the interfaces was studied, resulting in the different diffusion coefficient (D) for each element as diffusant in the sample heated at 550°C. As a filler, the Mg diffusing into the Al matrix has the greater D (=0.708 × 10^–16 m² s^–1) than Si (D = 0.231 × 10^–16 m² s^–1), while oxygen diffusing into the Mg has the highest D (=8.333 × 10^–16 m² s^–1). Further probing by using the X-ray diffractometer (XRD), the phase formation covering metal oxides and intermetallic compounds was identified in the samples. Hardness test on the sample’s surface indicates the variation of Vickers hardness number (VHN) at several points on the sample’s surface.