Laser powder bed fusion of planar bi-metallic thermally auxetic lattice structures

Abstract

This study addresses challenges in design and fabrication of thermally auxetic structures with zero thermal expansion (ZTE) using multi-material laser powder bed fusion. Planar 316L-CuCr1Zr lattices with re-entrant and triangular unit cells were designed, manufactured and tested. Introducing beam curvature as a new design parameter effectively reduces the coefficient of thermal expansion (CTE) compared to standard designs with straight struts. Curved beams act like non-linear springs and allow accommodating internal strains in the lattice. Despite the slight thermal expansion differences of CuCr1Zr and 316L, a curved-beam lattice is identified that mimics Invar's CTE up to 200 °C.