Microstructure Evolution during Semi-Solid Rheo-Cast Process of Al-Zn-Mg-Cu Alloy Reinforced with Potassium Titanate Whiskers

Recent investigations have demonstrated that potassium titanate whiskers (PTW) as reinforcement can significantly improve the mechanical properties of aluminum alloys. Building on these findings, 7xxx alloy-5.0 vol% PTW composites were fabricated via rheological processing, with characterization conducted on microstructural evolution during solidification. With prolonged processing duration, PTW exhibits progressively improved dispersibility in the alloy matrix. Specifically, a 59.3% reduction in the average whisker length was observed following 30 s of semi-solid slurrying, attributed to the shear-induced fragmentation during the treatment. Meanwhile, the composite’s tensile strength reached 363.0 ± 3.7 MPa, gaining ca. 29.0% increase. Findings from this study demonstrate that high-performance Al-PTW composites can be fabricated via semi-solid rheological processing, concurrently enabling a reduction in PTW reinforcement content. Additionally, this research deepens the comprehension of PTW breakage and distribution mechanisms during the solidification of semi-solid aluminum melts.