Simulating additive manufacturing thermal cycling via dilatometry: A methodology to assess intrinsic heat treatment effects on microstructures

Intrinsic heat treatments (IHTs) inherent to additive manufacturing (AM) processes play a critical role in determining as-built microstructures; however, their experimental reproduction remains challenging. In this work, a methodology was developed to experimentally simulate a representative AM thermal history experienced by a single point within a printed layer using a high-resolution dilatometer. The thermal profile was constructed by combining finite element predictions of thermal evolution with experimentally reported temperatures from literature. After optimising the sample geometry and dilatometer configuration, heating and cooling rates above 1350 and 950 °C/s, respectively, were achieved, representing some of the highest rates reported for ex-situ simulation of laser powder bed fusion (LPBF) IHTs. The methodology was validated by comparing heat-treated samples with the last printed layer of an LPBF-produced maraging steel through dilatometry, X-ray diffraction, electron microscopy, chemical analysis and hardness measurements. The results show that key post-solidification microstructural features, including retained austenite content and hardness response, can be successfully reproduced. However, identifying transformation temperatures under such extreme conditions remains challenging, and certain solidification-driven features cannot be fully replicated. Overall, the proposed methodology provides an experimentally accessible framework for investigating process-microstructure relationships under representative AM thermal conditions and has the potential to be extended to other AM alloy systems through appropriate selection of thermal histories, processing conditions and material-specific calibration.