Abstract:In this paper, the amount, distribution and morphology of δ phase in the alloy were controlled by cold deformation and aging treatment without changing chemical compositions of Inconel 625 superalloy to ensure the microstructure stability and performance reliability of the alloy. The influence of cold deformation (ε) on the amount, distribution and morphology of δ phase precipitation and the precipitation of δ phase on the microstructure and properties of Inconel 625 superalloy tubes are investigated by room temperature compression tests plus aging treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM) and, energy dispersive spectrdmeter (EDS) is utilized to analyze the δ phase characteristics. It is found that with the increase of cold deformation (ε), the average grain size decreases and the deformation uniformity of the grain becomes better gradually, and the hardness increases. Cold deformation (ε) promotes precipitation of δ phase. With the increase of cold deformation (ε), the δ phase first precipitates at the deformation twin and grain boundaries as well as deformation bands, and then precipitates in the grains, the precipitation of δ needle phase were oriented in two near-orthogonal directions or a lattice-like distribution within the grain and the δ phase were oriented in two parallel directions at the deformation bands. At the same time, the morphologies of δ phase change gradually from needle to spheroid or short rodlike with increasing cold deformation (ε).The average grain size of the alloy reduces with the increase of cold deformation (ε) and the extension of aging time (t). The hardness of the alloy increases with the extension of aging time (t) at ε=35 %, however, the hardness of the alloy has no obvious change ε≥50 %.