Thermal stability of TiNi and TiNiCu alloy memory springs under constant loads

TiNi alloy based memory springs are promising actuators for engineering applications. This paper discusses the thermal stability of TiNi and TiNiCu alloy memory springs under different loads and at various temperatures, heated by direct current. The research results showed that, in the first few thermal cycles under constant load, the stroke of the spring decreases, but it remains almost constant with further thermal cycles. For TiNi and TiNiCu alloy memory springs, over-heating and over-loading leads to the deterioration of thermal stability due to plastic deformation. Under the same constant load, TiNi alloy springs showed better thermal stability than TiNiCu alloy springs because precipitation of Ti3Ni4 particles strengthens the matrix.