Microstructure and properties evolution of Cu-Ti-Cr-Mg alloy during equal channel angular pressing at room temperature and cryogenic temperature

A Cu-2.5Ti-0.4Cr-0.1Mg (wt%) alloy was prepared in a vacuum medium frequency induction furnace. The evolution of the microstructure and mechanical properties of the samples deformed by equal channel angular pressing (ECAP) at different temperatures was investigated by hardness tests, tensile tests, optical metallography observation, X-ray diffraction and electron back-scattered diffraction. The cryogenic-temperature-deformed (CDed) samples have a little higher hardness than room-temperature-deformed (RDed) samples at any given ECAP pass. After 8 ECAP passes, the yield strength of CDed and RDed samples is close to each other, with the value of 812 ± 17 MPa and 793 ± 25 MPa, respectively. ECAP deformation significantly refines the grain size of the alloy due to the dislocation subdivision and twin fragmentation, and the average grain sizes of RDed and CDed samples after 8 passes are about 0.32 µm and 0.37 µm, respectively. Calculation results show that dislocation strengthening plays a key role in increasing the strength of ECAPed samples.