Abstract
The binder phase (γ) of WC-Co type sintered alloys has been accepted as fcc metal. However, it was found that under the external stresses the binder phase of the alloys in particular with high carbon content transforms easily into ε phase (hcp) at low temperatures. The signficant influences of the transformation on the low temperature properties such as elastic and plastic behaviors, strength, ductility, as well as various physical properties including lattice defects have been suggested.