A high purity(99.999%) copper single crystal was grown in an Ar. atmosphere by Bridgman method. The grown crystal dimensions are 36mm in diameter and 40mm in length. And cross section perpendicular to growth direction is {100} plane.
Three bend specimens were prepared by wire spark sectioning and isothermal annealing was performed to lower the initial dislocation density at 1050℃. Three point bend test was performed by Instron machine with constant displacement rate.
To investigate the crack tip plastic deformation patterns, dislocations at the crack tip were observed with etching techniques before and after the test.
The results show that dislocations nucleate at the crack tip and propagate along the special directions, and severe plastic deformations were observed even at the start of the test.
