An observation of the effect of grain structure on the appearance of Kirkendall porosity.

Study of substitutional diffusion in thoriated and nonthoriated nickel alloys, particularly in several nominally Ni-20Cr-2ThO2:Ni type diffusion couples diffused at 1530 K. Upon metallographic examination, one DS-NiCr:Ni couple had negligible Kirkendall pore formation while the other couples contained significant porosity. It is believed that the difference in Kirkendall porosity is related to the unique grain structure of the particular lot of DS-NiCr used in this diffusion couple.