Abstract
Structural changes in copper single crystals during high temperature creep deformation were investigated by means of the Berg-Barrett method. Creep tests were performed in argon atmosphere at 0.75 Tm=745°C and 0.85 Tm=880°C (Tm : the melting temperature in degrees Kelvin). In order to obtain the three-dimensional information on the substructures, two kinds of observation surfaces were prepared by cutting the specimens crept to various strains electrochemically : one parallel to the primary slip plane (111) and the other parallel to the (\bar101) plane on which deformation bands due to the primary slip are formed. A third observation surface is the original specimen surface, i.e. the (1\bar21) plane which is normal to the lattice rotation axis in the deformation band.
In the transient creep stage pillar-like subgrains elongating in the direction of [1\bar21] were observed. They were surrounded by sub-boundaries parallel to the (111) and (\bar101) plane which were twist and tilt boundaries, respectively. Spacings between the sub-boundaries were about 30∼50 μ at 745°C and 50∼100 μ at 880°C; the spacings remained almost the same throughout the steady-state creep stage. In the examination of the (111) plane, apparent lattice twisting of the (111) plane about the [1\bar21]-axis was found with a period of about 10 μ. The increase in the twist angle was the most remarkable structural change during creep deformation.
