Influence of Si and Ti contents on the microstructure, microhardness and performance of TiAlSi intermetallics in Al–Si–Ti alloys

In this study, the influence of Si and Ti contents on the microstructure, microhardness and morphology of TiAlSi intermetallics in ternary Al–Si–Ti alloys was investigated. The increase of Si addition in Al–xSi–2Ti alloys leads to an increase of Si content in TiAlSi phase as well as an increase of microhardness. A phase evolution from Ti(Al1−xSix)3 to Ti7Al5Si12 at about 14 wt.% Si was detected, while all the TiAlSi intermetallics exhibit flake-like. The increase of Ti content promotes the morphological transformation of TiAlSi from flake-like to block-like and primary Si particles are replaced by blocky TiAlSi particles in hypereutectic Al–Si alloy. The high-temperature strengthening effect of TiAlSi particles in a piston alloy was investigated and the strength is increased by 11.9% in this article, while the elongation and yield strength are increased by 17.6% and 10.1%, respectively.

► Influence of Si and Ti contents on TiAlSi intermetallics in Al–Si–Ti alloys was investigated.
► Increase of Si content leads to a composition and phase evolution.
► Microhardness of TiAlSi increases with Si content in the alloy.
► Increase of Ti content promotes a morphological transformation.
► Blocky TiAlSi particles are helpful to improve the properties of a piston alloy.