The myth of hydrogen pores in aluminum castings

Abstract

The equilibrium solubility of hydrogen in liquid and solid aluminum is reviewed. Homogeneous and heterogeneous nucleation of hydrogen as pores are evaluated. It has been determined that homogeneous nucleation of hydrogen pores is impossible. Moreover, in situ observations of pore formation in melts with high hydrogen contents are inconsistent with heterogeneous nucleation of hydrogen pores. The only mechanism for hydrogen to contribute to pore formation is the inflation of bifilms by diffusion. Hence, in the absence of bifilms in the melt, measuring and controlling hydrogen content in the melt would be unnecessary.