Morphological evolution of ZrAlSi phase and its impact on the elevated-temperature properties of Al–Si piston alloy

• Morphology evolution of ZrAlSi phase in Al–18Si–xZr alloys was detected.
• The morphology transforms from flake-like to block-like with Zr content.
• Effect of different morphological ZrAlSi on the properties of an A–Si piston alloy was studied.
• Blocky ZrAlSi phase is good for the elevated-temperature tensile strength.

It is investigated that the morphologies of ZrAlSi phase in Al–18Si–xZr alloys will evolve from flake-like to block-like with increasing Zr content and the precipitation of the ZrAlSi intermetallic decreases the volume fraction of primary Si phase. The effect of flake-like and block-like ZrAlSi phase on the microstructure and elevated-temperature mechanical properties of an Al–Si multicomponent piston alloy was also investigated. It was found that flake-like ZrAlSi particles lead to a decrease of 7.28%, 3.23% and 8.85% for the elevated-temperature tensile strength, elongation and yield strength of the piston alloy, respectively, whereas block-like particles cause an increase of 15.82%, 12.94% and 14.75%, respectively. Meanwhile, the linear expansion is almost unaffected.