Microstructure features and mechanical properties of non-heat treated HPDC Al9Si0.6Mn–TiB2 alloys

This study aimed to enhance the mechanical properties of high pressure die casting (HPDC) Al9Si0.6Mn alloys by incorporating in-situ TiB2 particles. The effects of TiB2 addition on the microstructure and mechanical properties of as-HPDC Al9Si0.6Mn alloys were investigated. The results showed that TiB2 addition refined the bimodal grain structure and eutectic Si morphology in the central region of the as-HPDC alloys, which was the primary contributor to the mechanical properties. The thickness of the skin region and band zone increased with increasing TiB2 addition, while the central region exhibited a reduced thickness but remained dominant on the entire cross-section. The optimal TiB2 content was found to be 1 wt%, resulting in the 23.4 % reduction in grain size and 10.7 % enhancement in yield strength. The modified strengthening model based on the microstructure features of the central region accurately predicted the yield strengths of as-HPDC alloys. Finally, the morphological strengthening factors induced by TiB2 particles were analytically illustrated in the HPDC Al9Si0.6Mn–TiB2 alloys.