The Role of Melting Pool Boundary in the Determination of Mechanical Property of Al Alloys Made by Selective Laser Melting

摘要

Most of Al alloys made by selective laser melting (SLM) only have comparable tensile properties to conventional casting alloys although they have much finer microstructure. The inherent problem was not revealed and therefore there was no breakthrough in processing high-strength Al alloys by SLM. In SLM, the parts were built through the overlapping of multi-track and multi-layer molten pools of metal powders. The condition of metallurgical bonding among these melting pools (MP) is a key essential issue to obtain good tensile properties. This study selected popular AlSi10Mg alloy as a reference alloy and investigated the role of melting pool boundaries in obtaining good tensile properties. Three type of molten pool boundaries were obtained by changing the scanning direction of samples (horizontal, vertical and 45º): “track–track”, “layer–layer”, coexisting “layer–layer” and “track–track”. The phase composition in these three types were same, consisted of eutectic and α-Al. However, the microstructure were different. The “track–track” melting pool was characterized by homogenous cellular microstructure while the “layer-layer” was characterized by orientational eutectic and α-Al. The coexisting “layer–layer” and “track–track” melting pool have both type of microstructure. A discussion will be addressed in details.