Texture, anisotropy in microstructure and mechanical properties of IN738LC alloy processed by selective laser melting (SLM)

摘要

Nickel-based IN738LC samples were built by selective laser melting (SLM). To evaluate the anisotropic mechanical behavior of IN738LC material due to layer-wise build up, specimens were built with their cylinder axis (loading direction) oriented either parallel to the building direction, or perpendicular to the building direction and at 45° to the laser scanning direction. After building up the specimens by SLM, they were investigated either under the 'as-built' condition or after heat treatment and compared to IN738LC cast material. The analysis of microstructural anisotropy in SLM made IN738LC specimens was done by using EBSD, EDX and X-ray texture analysis methods, and then correlated with anisotropic material behavior observed during tensile and creep testing at room temperature and 850 ℃. All SLM samples possess the same general texture, with the majority of grains forming one single component of a cube texture with one of the cubic axes parallel to the building direction, and another cubic axis parallel to the laser scanning direction. The Young's modulus determined during tensile testing is significantly lower parallel to the building direction than perpendicular to the building direction, with the values for cast IN738LC material in between. Creep behavior of specimens with loading parallel to the building direction is superior compared to specimens with loading axis normal to the building direction. The anisotropy of Young's modulus was modeled based on the single crystal elastic tensor and the measured crystallographic preferred orientations, and compares well with the data from tensile tests.