Control of surface micro−structure for Al alloy/polymer joining fabricated by laser process using Al−Ti−C powders: Effect of powder composition.

Abstract

Surface micro−structure for joining with thermoplastic parts was additively manufactured on an aluminum alloy (A5052) substrate by laser scanning on Al−Ti−C powder mixtures. The micro−structure consisted of particle−shaped protrusions with a few hundred micrometers. The effect of C content in Al−Ti−C powder mixtures on the micro−structure and constituent phases was investigated. The fraction of particle−shaped protrusion reached maximum when the C/Ti molar ratio was 0.8. Adhesiveness between the particle−shaped protrusions and A5052 substrate decreased drastically when the C/Ti molar ratio increased from 0.6 to 0.8. Changes in these structural factors were related to the formation of TiC and Al3Ti phases after the laser−irradiations. The A5052 substrate was joined with Polyamide−6 sheets via the micro−structure by hot−pressing. When the C/Ti molar ratio was 0.6, the joint strength reached maximum since both the fraction of particle−shaped protrusions and adhesiveness between particle−shaped protrusions and A5052 substrate were high. The constitute phases (TiC and Al3Ti phases) in the micro−structures were assessed by Scheil simulation for Al−Ti−C system to calculate the component partitioning and solidification path during solidification. These results were used to discuss the relation between the surface micro−structure and powder compositions.