CU-ZN-AL-NI SHAPE MEMORY ALLOY AND PROCESS FOR PREPARING THE SAME

摘要

The invention relates to a Cu-Zn-Al-Ni memory shape alloy used for manufacturing active elements for thermal or electrical actuators with the property to memorize two hot shapes, and to a process for preparing the same. According to the claimed invention, the alloy exhibits two hot shapes in the temperature ranges within 30...80°C and 100...280°C, respectively, producing a specific mechanical work within 55...75J/kg and has the following composition expressed in percentage by mass: 72.5...73% Cu, 20...21% Zn, 6.4...7.4 % Al, 0.5...1.2 % Ni, max. 0.3% impurities and a %Al/%Ni ratio = 5...10. The claimed process consists in smelting the alloy in a medium frequency oven by melting in a first stage 70% of the copper and nickel amount necessary for alloying, under protective flux consisting of 40% CaF+ 30% NaCO+ 20% NaBO+ 10% NaCl added in a ratio of 2% of the total charge, the alloying with Zn and Al and the completion with the remainder of Cu being achieved progressively under the formed flux, at the temperature of the copper bath of 1150°C, afterwards the melting charge is cast in metal moulds ensuring a cooling speed of at least 40°C/min, the alloy being subjected to several plastic deformations by rolling at a temperature of 700°C with instantaneous cooling in water, after each passage.