Effects of particle size, bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting

In recent years, metal matrix syntactic foams (MMSFs) have become highly attractive owing to their unique physical, microstructural and mechanical features. Due to their promising potential for different industrial areas like automotive, aviation, and defense, these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams. Differently from previously reported laboratory scaled techniques in the literature, this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique. Accordingly, 1–2 mm, 2–4 mm, and bimodal (50vol.%) natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine. Physical, macroscopic, and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony. Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm⁻³ depending upon the pumice particles size interval. To assess mechanical responses, quasi-static compression tests were performed. Furthermore, half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes. Results indicate that although the heat treatment enhances the compressive strength, plateau stress, and energy absorption properties of the fabricated foams, it changes damage mode of the samples by causing brittle dominant deformation.