Effects of Hole Cold Expansion on Fatigue Behaviors of AlSi10Mg Plate Manufactured by Selective Laser Melting

The fatigue life of metal part manufactured by selective laser melting is generally poor. Cold expansion technique is an effective approach to advance the fatigue performance of hole structures. This paper proposes a mandrel cold expansion process to advance the fatigue performance of AlSi10Mg hole plates fabricated by selective laser melting. A finite element analysis was performed to investigate the hole plate cold expansion approach. The influences of cold expansion on the surface roughness, residual stresses and fatigue behaviors of the plates were discussed. The results indicate that compressive residual stresses are introduced at both the cold-expanded hole inlet and outlet. The compressive residual stresses at the outlet surface are higher than that of the inlet surface. The cold-expanded hole plate presents a large compressive residual stress region in the transverse direction, which leads to the fracture of the specimen changes from the transverse to the longitudinal direction. In addition, the cold expansion reduces the surface roughness Ra of hole wall. The fatigue performance of the additive manufactured AlSi10Mg plate is improved at low cold expansion degrees.