529 CHINA FOUNDRY Vol. 18 No. 6 November 2021 Research & Development *Çağın Bolat, İsmail Cem Akgün, Ali Gökşenli Faculty of Mechanical Engineering, Istanbul Technical University, 34437, Istanbul, Turkey 1 Introduction Syntactic foams (SFs) are versatile engineering materials which consist of polymer/metal matrix and thin-walled hollow ceramics or cellular-structured oxides [1,2] . Although polymer matrix syntactic foams (PMSFs) have been investigated by many researchers and their commercial usage has been underway for some time, this case is not valid for metal matrix syntactic foams (MMSFs), and fabrication efforts have only remained on a laboratory scale. In literature, MMSFs are not only classified as a subgroup of conventional closed-cell metallic foams, but also interpreted as advanced particle reinforced composite Abstract: 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 flled 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/fller 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 infuences 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. Key words: pumice; cold chamber die casting; syntactic foam; bimodality; damage characteristic CLC numbers: TG146.21 Document code: A Article ID: 1672-6421(2021)06-529-12 *Çağin Bolat Male, born in 1989, a Ph. D candidate and research assistant in the Istanbul Technical University. His research interests mainly focus on metal matrix syntactic foams, casting technologies, and aluminum alloys. He has published eleven papers in different indexes such as SCI, ESCI, Scopus, etc. E-mail: caginbolat@itu.edu.tr Received: 2021-07-20; Accepted: 2021-09-09 https://doi.org/10.1007/s41230-021-1133-4 Effects of particle size, bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting foams [3] . Due to their perfect energy absorption capacity [4] , good elongation [5] , weight reduction potential [6] , and high impact resistance [7] , MMSFs have become attractive in recent years for many different industrial areas such as automotive (crash boxes assembled in the front panel), aerospace (fuselage parts on the airplane), marine (submarine hulls), and defense (special armors placed in the core of sandwich composites for ballistic performance). Compared to other alternatives like iron [8] , zinc [9] , magnesium [10] , and titanium [11] , aluminum alloys (especially the A356 system [2,3] ) are the most preferable metals as a matrix due to their widespread usage, low density, and good casting ability. Furthermore, when reinforcement ceramics are analyzed, two different models are noticed: thin-walled hollow spheres and porous/cellular-structured particles. In the category of hollow spheres, thin-walled Al 2 O 3 , SiC, and glass spheres have been utilized by different investigation groups [12-15] . Even though this kind of special fllers display suffcient