CFD modelling of nitrogen gas flow pattern during sintering of Al–7Zn–2.5Mg–1Cu alloy and its effect on distortion

The effects of gas flow pattern on the distortion in Al–7Zn–2.5Mg–1Cu alloy were experimentally examined by sintering three rectangular samples, equally spaced 2–40 mm, in each batch at 620°C for 45 min under flowing nitrogen. A three-dimensional (3D) computational fluid dynamics (CFD) model was developed to investigate the gas flow behaviour surrounding three samples during isothermal sintering. Streamlines, gas flowrate into each cavity between two adjacent samples and wall shear stress distribution along the surfaces of each sample were found dependent on sample separation distance. The flow patterns could affect the distortion levels of the three samples by changing the oxygen content in the local sintering atmosphere and the evaporation rates of Mg and Zn from the sintering surfaces. The 3D CFD model developed was also applied to the experimental design of the sintering of six samples to ensure minimum distortion as well as maximum densification.