Characterization of texture and grain boundary character distributions of selective laser melted Inconel 625 alloy

Abstract

Select laser melting (SLM) is one of the practical metal additive manufacturing processes to fabricate complex structures. The inhomogeneous microstructure and high residual stress are typically resulted from a non-uniform melting and rapid solidification during a SLM process, which has the significant impact on part dimensional instability, corrosion resistance, and mechanical properties. The bulk of current research is limited to the general characterization of grain size, texture, and mechanical properties. However, grain boundary character distribution (GBCD) and its relationship with texture are yet to be understood. This study has shown that the preferred 〈110〉 along building direction and 〈100〉 along laser scanning direction were produced. The high density of low angle grain boundary (LAGB) can be an indicator of residual stress levels in the as-SLMed samples. The newly-developed ∑3, ∑9 and ∑27 grain boundaries were heavily populated, and the cluster of grains interfaced by ∑3n (n = 0, 1, 2…) was introduced at the expense of LAGB only at high recrystallization annealing (1150°C or over). The research results suggest that GBCD optimization be possible in the SLMed Inconel 625 alloy via suitable post annealing, which allows improving intergranular corrosion resistance and enhancing mechanical properties.