Mechanism of α-Cr precipitation and crystallographic relationships between α-Cr and δ phases in Inconel 718 alloy after long-time thermal exposure

摘要

To study the precipitation mechanism of α-Cr phase in Inconel 718 alloy,the samples after long-time aging at 650 and 677°C were examined by microstructural observations and chemical phase analysis methods.Combining the thermodynamics and kinetics calculation results,α-Cr always precipitates in the vicinity of δ phase,because δ phase rejects Cr into the γ-matrix when growing.The selected area diffraction patterns confirm that the crystallographic relationships of α-Cr with δ phase are(010)δ//(1 10)α-Cr and [100]δ//[111]α-Cr.A graphic model is also presented to show the crystallographic relation between α-Cr and δ phases.