The effect of Ni, Co and Cr on the primary particle structure in Cu–Al–Nb–X shape memory alloys

Niobium, cobalt and chromium have a very low solubility in a Cu–Al alloy. Therefore, primary particles were observed in the martensitic matrix of this alloy. The kind, size and number of the primary particles depend on the alloying element. The main particles were identified as Nb(Cu, Al)2. The characteristic feature of this phase is the presence of stacking faults. The number of stacking faults depends on the chemical composition of these particles. This phase includes up to 7 Ni, 11 Co or 10–22 Cr (at.%). Moreover, small oval particles of AlNi, AlCo and Cr phases were identified. Changes in the chemical composition of the Nb(Cu, Al)2 phase as well as the presence of AlNi, AlCo and Cr particles cause changes in the mechanical and physical properties of the alloys studied.