Abstract
In the present investigation the coefficient of diffusion of silicon and phosphorus in solid iron were measured and the effects of carbon on this coefficient studied.
The results obtained were summarized as follows;
1) The coefficient of diffusion of silicon is 7×10-5 sq. cm. per day at 1000°C; 15×10-5 at 1050°CC;35×10-5 at 1100°C; and 56×10-5 at 1050°C.
2) The coefficient of diffusion of phosphorus is 9×10-5 sq. cm. per day at 1050°C; 21×10-5 at 1100°C; 33×10-5 at 1150°C; and 70×10-5 at 1200°C.
3) Both coefficients of diffusion of silicon and phosphorus increase appreciably when diffused simultaneously with carbon in the same direction, while they decrease markedly in the opposite, direction.
4) The heat of diffusion which was determined graphically from the variation of coefficient of diffusion with temperature is 48, 200 cal. per gram atom for silicon and 52, 300 for phosphorus. These value are in accordance with the Dushman-Langmuir equation.
5) The diffusion equation may be written:
Dsi-γFe=18, 000.e-48, 200/RT
Dr→γFe=42, 000.e-52, 300/RT
for silicon and phosphorus, respectively, in which D is the diffusion coefficient, in sq. cm. per day, e the base of the natural logarithms, R the gas constant and T the absolute temperature.
