Transformation kinetics during heat treatment of additive manufactured alloys AlSi10Mg & X5CrNiCuNb16-4

In this work, additively manufactured metal alloys are compared to their conventionally produced counterparts. The heat treatment of two different laser beam melted alloys, namely the aluminium cast alloy AlSi10Mg (EN AC-43000) as well as the martensitic precipitation hardening steel X5CrNiCuNb16-4 (17-4 PH) are investigated. The conventional samples are high pressure die cast for the aluminium alloy, while the steel was hot rolled. The microstructure of additively manufactured aluminium samples (as-built) shows a similar eutectic structure like the as-cast condition, however in a much finer scale. During standard heat treatments, the focus is on analysing the differences in kinetics of precipitation and dissolution transformations. The kinetics are investigated by Differential Scanning Calorimetry and Dilatometry. Both LBM materials show significant shifts of the characteristic transformation temperatures. Heating the additively manufactured aluminium samples (as-built condition) leads to higher characteristic transformation temperatures compared to the conventional material. The rapid solidification during LBM results in a higher supersaturation and thus to a more pronounced exothermic precipitation during heating, compared to the as-cast condition. Similar differences have been found for the steel.