Diffusion in Inert‐Gas Bombarded Pt and Al

Diffusion in inert‐gas bombarded Pt and Al is studied by gas‐release measurements, transmission electron microscopy, and depth‐distribution measurements. It is found that gas release in Pt exhibits three components with temperature ranges of ambient < 500, 500 to 850, and > 850°C of which the range 500 to 850°C coincides with the temperatures of Pt self‐diffusion and in turn leads to the value 57 to 64 kcal/mol for Δ H for Kr‐Pt. By contrast, Al is shown to retain inert gas up to the melting temperatur of 660°C. Transmission electron microscopy of Pt shows that the gas release at 500 to 850°C is accompanied by dislocation loop annealing, while that at > 850°C coincides with the occurrence of bubbles. The tendency of Al to retain gas is found to correlate with the appearance first of bubbles and then, at about 625°C, of large surficial blisters. Depth‐distribution experiments with Pt show that the gas remaining at temperatures where bubbles are present has a deeply penetrating, exponential form, whereas in Al heated above 465°C the gas is mostly concentrated near the surface. The theory of bubble diffusion is finally considered, and is shown to predict bubble motion over the temperature ranges inferred by the other observations, namely 7> 850°C for Pt and > 500°C for Al.