EFFECTS OF THE NUMBER OF EQUAL-CHANNEL ANGULAR PRESSING PASSES ON THE STRAIN RATE SENSITIVITY OF ULTRAFINE COPPER

摘要

Annealed tough-pitch copper was processed by eight passes of equal-channel angular pressing (ECAP) using route B_c. Pressed samples had a square section with a side length of 8 mm. Tension tests were performed at static loading with a strain rate variation by three orders of magnitude. The material was examined in the as-received condition and after 1, 4 and 8 passes. All standard mechanical properties (yield strength, tensile strength, fracture strain and contraction) were determined, and nominal and true deformation curves were plotted. In all cases, the strength properties (yield strength and tensile strength) grow as the tensile strain rate increases, while in general plastic properties (fracture strain and contraction) tend to decrease. The strain rate sensitivity coefficient was found to grow with the number of ECAP passes.