Production of Cu-11.85Al-3.2Ni-3Mn shape memory alloy by spray forming process

Abstract

The shape memory alloys are able to recover its original shape after being plastically deformed. The technological applications of these alloys comprehend several areas such as medical, security, and robotics. The most commonly used alloys are based on composite Ni-Ti. However, these alloys are very reactive with oxygen, and also show a large hysteresis and thermal stress. Moreover, the Cu based alloys have advantages over NiTi alloys, because of the reduced cost of the alloy elements, the lower hysteresis and thermal stress, and also because of the low reactivity with oxygen. The main difficulty in the production of these alloys is the requirement of high cooling rates for the initial removal of the ß phase, of high temperature, which decomposes in the phases ± and ³2 at 565°C, and deteriorates the properties of the material. This transformation can be averted during fast cooling, allowing the ß-phase to undergo a martensitic transformation only at temperatures above room temperature. On the other hand, the spray forming is a rapid solidification process, in which a stream of molten metal is atomized by injecting an inert gas at high speed, generating drops of various sizes, which are rapidly driven toward a metallic or ceramic substrate, and then collected in a liquid, solid or partially solid state, generating a coherent deposit almost fully dense deposit. During the process, cooling rates in the range of 103-105K/s can be achieved. Thus, this project proposes to use the spray forming process in the processing of copper base alloy Cu-3.2Ni-11.85Al-3Mn aiming the shape memory effect.