Effect of reactive elements on porosity in spray-formed copper-alloy Billets

In spray-formed preforms, porosity is unavoidable. This is because the atomising gas becomes entrapped during the process. Normally, nitrogen is used for atomisation and therefore the voids are filled with this gas, which is not soluble in copper. To obtain a dense material after further forming processes such as extrusion, forging or drawing, porosity has to be limited to a specified level. are means to influence porosity inside the spray-formed billet. To a certain extent, porosity can be influenced by process parameters. Reactive elements inside the alloy have an additional effect, that is reaction of elements such as Zr, Ti, Al with the entrapped nitrogen. Until now, a detailed explanation has not been given, however, a theory of hot porosity formation is presented in this paper. The calculated content of nitrogen and titanium-nitride is verified using analytical methods. The addition of titanium into the melt can reduce porosity by a factor of three.