Investigations on the Thermal Expansion Properties of High-Relative-Density Invar 36 Alloy Fabricated by Laser Powder Bed Fusion

In this study, five near fully dense (relative densities > 99.75%) Invar 36 samples were fabricated by laser powder bed fusion (LPBF) technology under the constant laser energy density (E_v) of 78.1 J/mm³. The effects of laser power and scanning speed on the thermal expansion behavior of these samples were investigated. The results indicate that under the same E_v, the average coefficient of thermal expansion (CTE) of fabricated sample at 150 W and 600 mm/s is only 0.14 × 10^–6/°C (− 60 ~ 25 °C), 0.37 × 10^–6/°C (25 ~ 100 °C), and 1.58 × 10^–6/°C (25 ~ 200 °C). Its significantly lower CTE values attributes to larger residual stress, which can enhance the spontaneous volume magnetostriction of invar 36 alloy. The lager residual stress is induced by the competitive growth of grains at the overlap of molten pools and inadequate remelting of shallower molten pools. This study provides profound insights into the understanding of the thermal expansion behavior of invar 36 alloys, laying the foundation for the fabrication of high-performance invar 36 alloy components in the future.

Graphical Abstract