The influence of the doping elements on the structure and the martensitic transformations in the Ti50-2xHfxZrxNi50-2xCuxCox shape memory alloys

The structure and the martensitic transformation were studied in the Ti50-2xHfxZrxNi50-2xCuxCox alloys. An in-crease in X parameter from 1 to 17 changed the configuration entropy from 0.89R (low-entropy alloy) to 1.79R (high-entropy alloy). All alloys crystallized in (Ti,Hf,Zr)50(Ni,Cu,Co)50 phase which occupied more than 90 % of the volume. The chemical composition and the volume fraction of precipitates depended on X parameter. If X is equal to 10, (Ti,Hf,Zr)2(Ni,CuCo) particles were observed; if X = 17, the (Ni,Cu,Co)4(Ti,Hf,Zr)3 precipitates were found. An increase in X parameter decreased the temperatures of the martensitic transformation. If X >= 10, the martensitic transformation was not found on cooling to-170 degrees C.