Abstract
The temperature dependences of Vickers hardness of tungsten, molybdenum and the reactor pressure vessel steel (Coltuf-28) were examined in comparison with the geometrical characteristics of the deformation around the impression by using a salerometer.
As a result, it is made clear that the deformation range (lm) around the impression increased generally with increasing temperature for a constant size of impression (dm) and became maximum between the two junction points in the logHV-1/T relation, and that the rise height (hm) around the impression indicated the maximum between the above mentioned junction points and decreased abruptly above that temperature.
It is made clear that the average surface strain (ε) obtained from the deformation around the impression is generally 2∼5% for most materials and becomes maximum between the above mentioned junction points for a constant deformation range (lm) and decreases at other temperatures.
It is considered that the plastic strain increases abruptly with increasing temperature over the temperature range between the two junction points in the logHV-1/T relation. This corresponds to the abrupt increase in the strain and the reduction of area in the tensile test.
