The Formation Mechanism of Porosity for Spray-deposited 7075 Alloy

The distribution model of temperature for the billets was established based on the porosity formation mechanism. By calculating the numerical relationship between the temperature of the deposition layer and the formation ability of the porosity, the distribution of porosity for spray formed 7075 aluminum billets was predicted and the influence of superheat on the formation probability of porosity was analyzed. The results show that a denser billet can be obtained with the average temperature of 813 K of the droplets and a liquid fraction of 50%. The porosity would increase whether the temperature further increased or decreased. Finally, the 7075 aluminum alloy was prepared by spray deposition technique with the optimum process parameters. It can be found that the distribution and types of the porosity were different at different locations. These results are in good agreement with the porosity distribution law.

Keywords:
spray deposition; superheat; porosity distribution; formation mechanism