In-situ 3D visualizations of microstructural evolution during hot-pressing sintering of 7055 alloy powders containing satellite particles

In this study, we developed an in-situ hot-pressing sintering (HPS) device that can be coupled to a laboratory X-ray microscope, offering laboratory-available observation of the morphology evolution. With the help of this device, in-situ three-dimensional (3D) visualizations of the microstructural evolution of 7055 aluminum alloys during the HPS process were conducted. The 3D results revealed that the two-dimensional (2D) methods usually underestimated sintering neck width and exhibited significant standard deviation in statistical analysis. Benefiting from the precise microstructure characterization of the in-situ 3D methods, the diffusion activation energy for the sintering of 7055 alloys was calculated, and the quantitative relationship between the sintering temperature and the sintering process was constructed. Moreover, it was experimentally found an accelerative effect of satellite particles on the sintering process, and its mechanisms were discussed. The satellite particles enhanced the curvature near the sintering neck and thus increased the sintering driving stress, promoting the densification process. These findings provide new insights for optimizing sintering processes.