Effect of aluminum alloying on the structure and properties of rapidly quenched TiNiCu alloy

The efficiency of shape memory alloys for the MEMS technology has been recently demonstrated. Quasibinary intermetallic TiNi-TiCu alloys produced by rapid quenching from liquid phase in the form of thin (about 40 um) ribbons are an attractive material for the fabrication of micro-actuators due to their narrow temperature hysteresis of the shape memory effect (SME) and relatively large recoverable strain. In order to broaden the functionality of SME microdevices, in this work we have alloyed TiNiCu containing 25 at.% copper with aluminum. The results have shown that alloying with 0.6 at.% Al increases the cast characteristics of the composition and favors its amorphization. Upon crystallization by isothermal annealing or electropulse treatment the resultant microstructure and SME properties of the Al containing alloy change but slightly in comparison with the original alloy however there is a significant shift (by more than 15°C) of the SME temperature range toward lower temperatures.