AWJ cutting of copper processed by ECAP

Copper samples, processed by equal channel angular pressing (ECAP), were cut using abrasive water jet (AWJ) and the cut walls were investigated. The aim was to prove a relation between AWJ declination angle and selected material properties, especially hardness, strength, and grain size. Three groups of samples were cut: the first one just after pressing (fresh samples), the second one after 1 month past ECAP application, and the third one after 6 months after ECAP processing. The comparison shows the following results. Just after the ECAP process, the declination angle increases with increasing number of passes through the ECAP die, i.e., the characteristic material properties (strength and hardness) increase throughout the tested angle range. The character of relations between number of passes and investigated parameters, such as declination angle, hardness, or strength, is parabolic for 1-month-old samples, with maximum around eight ECAP passes. The last group of samples, cut after 6 months after their preparation, does not indicate simple relations between number of ECAP passes and either the declination angle or material parameters, namely hardness. The mutual comparison of a theoretical model based on values of material properties from measurements and literature and experiment shows maximum relative uncertainty 5.9 %. This result proves that declination angle measurement on striations present on cut walls of AWJ can be used for evaluation of hardness, strength, and grain size.