Triply periodic minimal surfaces (TPMS), structures fabricated from Inconel 718 (In718) via selective laser melting (SLM), found their potential applications in the aviation and energy industries owing to their excellent anticorrosive properties and thermal stability. However, the SLM process induces micro-segregation, anisotropic mechanical properties, and detrimental phases (Laves, \(\delta\) ) which degrade its mechanical properties. Although heat treatment has shown promising results for bulk In718 material, its impact on TPMS structures has received very limited attention. This research investigates the impact of standard heat treatments, including stress relieving (SR), homogenization plus ageing (HSA), and direct ageing (DA), on the properties of diamond and gyroid TPMS structures. The quasistatic compression tests were conducted in an Instron machine, and material characterisation was conducted in Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). HSA treatment has led to maximum improvement; the compressive strength and yield strength of diamond TPMS were improved by 58.55% and 93.5% respectively, due to the precipitation of strengthening phases ( \(\gamma^{\prime }\) and \(\gamma^{\prime \prime }\) ) and dissolution of detrimental phases. HSA and DA treatments led to stretch dominated deformation and higher energy absorption capacity. Conversely SR treatment has shown bending dominated deformation behaviour and degraded mechanical properties in contrast to the previous studies on tensile samples.
