Abstract
Low temperature deformation of powder metallurgical pure Mo and dilute Mo-Cr, Mo-W alloys are studied over the temperature range from 77 to 500°K by simple tension, stress relaxation and incremental unloading tests. The experimental results show that substitutional solute atoms do not affect the activation volume V* and the thermal component of the flow stress σ*, but affect flow stress σ through the athermal component σμ. From the relation Hk=4τ*V*, the kink energy Hk is calculated to be 0.58 eV both for pure Mo and Mo alloys. The activation energy H is deduced to be 1.40 eV at 500°K, which is in good agreement with 1.48 eV obtained from Seeger’s equation proposed for the Peierls-Nabarro process at low stress. It is concluded from the present results that low temperature deformation (T<500°K) is controlled by the overcoming of Peierls-Nabaroo hills by the nucleation of double kinks and that substitutional solute atoms increase only the athermal component of the flow stress.
