Ductile Cleavage Fracture of Molybdenum

Abstract

MOST metals other than those having a face-centred cubic structure show a more or less rapid transition from ductile to brittle behaviour as the temperature is lowered. Well above the transition temperature the fracture surfaces are mainly fibrous with only a few cleavage facets, but at intermediate temperatures fracture occurs by cleavage after a strain of a few per cent. So far little attention has been paid to the mechanism of this ductile cleavage fracture. Recently, we have examined cleavage facets and longitudinal sections of a number of fractured specimens in which cleavage occurred after straining about 10 per cent at room temperature at a rate of strain of 0.88 × 10⁻⁴ sec.⁻¹. The tensile specimens, which had grain diameters of about 2 mm., were prepared from arc-cast deoxidized molybdenum and were 0.1 in. in diameter¹. The results throw some light on the mechanism of fracture.