Specimens A, B, and C, of 0.040 in. diameter commercial molybdenum wire (Lot FW 13-40) were heat treated in the vacuum furnace. Internal friction studies of these specimens were carried out using a low frequency (approximately 1 cycle per second) torsional pendulum completely enclosed in a vacuum tank.

The embrittling effect of small pressures of oxygen during heat treatment suggests that the so-called “recrystallization embrittlement” of molybdenum is actually oxygen embrittlement. A worked structure or a small grained structure tends to reduce the embrittling effect of the oxygen present by dispersing the oxides over a larger surface area.