Effects of Ti addition on microstructures of melt-spun CuCr ribbons

The microstructure and resistivity of melt-spun CuCrTi ribbon were studied. The results reveal that the maximal size of the primary Cr particles in the microstructures is below 100 nm by 0.65%-3.8%Ti (mole fraction) addition and the resistivity of annealed ribbons of 0.65%-1.3%Ti addition can meet the need of the contact materials used by the medium-voltage vacuum interrupters. By contrasting the melt-spun microstructures to the annealed microstructures, the primary Cr particles do not grow up quickly in the annealing process. The X-ray diffraction studies reveal that alloying increases the amount of the solute in Cu and Cr phases and results in the increase of resistivity. By the thermodynamic analysis, adding Ti to CuCr29 alloys increases the critical supercooling of the liquid/solid transformation, which makes the critical radius of nucleation decrease and the rate of nucleation increase. As a result, the microstructure of CuCr ribbon can be further refined.