Influence of ball milling process on microstructure, mechanical and thermal expansion properties of ZrMgMoO/Al-40Si composites.

In this study, ZrMgMoO/Al-40Si (ZMMO/Al-40Si) composites with 15 wt% ZrMgMoO were fabricated by ball milling-vacuum hot pressing (VHP) processes. The effect of ball milling processes on the microstructure, compressive properties and coefficient of thermal expansion (CTE) of the composites were investigated. It is found that ball milling treatments of mixed ZMMO/Al-40Si powders refine the particles of ZMMO reinforcements and primary Si in ZMMO/Al-40Si composites and improve the distribution of ZMMO reinforcements in α-Al matrix, resulting in the increase of the compressive strength and the decrease of the CTE of ZMMO/Al-40Si composites. The highest compressive yield strength of 430.82 MPa and the lowest CTEs of 5.8 × 10/°C (RT - 400 °C) are obtained after ball milling for 8 h at 250 rpm, increasing by 145.9% and decreasing by 61.3% respectively compared with the compressive yield strength and CTE of Al-40Si alloy. Among the reinforcements commonly used in aluminum matrix composites, ZMMO reinforcement has the highest reduction efficiency for CTE of ZMMO/Al-40Si composite. The application of high-energy ball milling to refine the microstructure is a promising method that can simultaneously increase the strength and reduce the CTEs of ZMMO/Al-40Si composites.