The effect of different heat treatment approaches on the mechanical properties of a low-density Thermosilit ZA27 syntactic foam
Year: 2025
Type: article
Abstract: Metal matrix syntactic foam (MSF) has garnered significant attention due to its high strength-to-density ratio. While hollow particles are well-studied in this field, porous fillers remain underexplored. This study introduces Thermosilit, an innovative, low-cost porous filler. Thermosilit is ultralight, with bulk and particle densities of 0.101 g/cm³ and 0.195 g/cm³, respectively, and was compared to expanded Perlite. Results show that Thermosilit is similar to Perlite in density and strength, with minor differences. This research used 1-1.2 mm Thermosilit particles and ZA27 alloy to create a novel foam through counter-gravity infiltration. Twelve MSF samples were produced: three as-cast (AC), four with complete heat treatment (CHT), and four with partial heat treatment (PHT). The average foam density was 2.00 g/cm³, a 57% reduction compared to solid ZA27. Compression tests were performed to assess mechanical properties and the impact of different heat treatments. All samples exhibited typical stress-strain behavior, including elastic, plateau, and densification phases. AC and PHT samples showed a sharp stress drop after peak stress, with PHT samples displaying greater fluctuation. In contrast, CHT samples demonstrated steadily increasing stress due to aging, significantly enhancing energy absorption, plateau stress, and energy efficiency. Furthermore, scanning electron microscopy (SEM) was employed to examine the microstructure of the syntactic foams in all groups. The analysis showed that heat-treated and aged foam |(CHT) modifies the ZA27 alloy matrix from a multiphase dendritic structure to a more spheroidized morphology, leading to improved ductility. PHT samples showed increased 1% offset yield strength but reduced plasticity, while CHT improved ductility by altering the microstructure into a multiphase system. Optical analysis revealed brittle deformation in AC and PHT samples, while CHT samples exhibited a more ductile, layer-by-layer deformation mechanism.
Source: Results in Engineering
Institutions: Thi Qar University, University of Newcastle Australia
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,940
Funder: University of Thi-Qar
OpenAlex ID: W4410635430