Preparation, characterization and composition optimization design of laser powder bed fusion continuously graded Invar36/316L stainless steel alloys

It is of great significance for designing different material compositions and batch experimental research via using additive manufacturing. In this work, Invar36 and 316L stainless steel (SS) are used as raw materials, and a specially designed powder distribution system in a laser powder bed fusion (LPBF) equipment is used to prepare continuous gradient alloys (CGAs) of Invar36/316L SS. The effects of microstructure and properties variations when the ratio of two compositions of Invar36 and 316L SS are systematically studied. It is found that the grain size and morphology of the melt pool would vary with the composition, but there is no significant difference in the phase distribution. In addition, localized areas of CGAs show similar or even better mechanical properties, thermal expansion properties, or corrosion resistance than the two materials themselves. When the percentage of Invar36 content is 70% - 80%, the microstructure and grain distribution of the samples are relatively uniform, and the tensile strength and corrosion resistance of the material are greatly improved, while the coefficient of thermal expansion does not increase significantly. The results of this work provide a practical path for the composition design and high throughput experiments of multiple materials.