Preliminary Results of Copper Based Shape Memory Alloys Analyze Used for MEMS Applications

Shape memory alloys (SMAs) are commonly used in micro-electro-mechanical systems (MEMS). Having the unique shape memory, super-elastic affects and now damping capacity SMAs have become an important smart material for a broad range of engineering applications in last years. Copper based SMAs are promising alloys, based on the obtaining price and good characteristic properties. Shape memory alloys as thin films are used for fast actuation in applications due to their high surface to volume ratio comparing to bulk SMAs. In this paper two shape memory alloys based on copper, proposed as targets in different deposition processes to obtain MEMS and with different chemical composition, are analyzed through scanning electrons microscope (SEM), XRD and EDAX considerations after water quenching and recovery heat treatments. The martensite variants are dimensioned and 3D aspects are also analyzed for both metallic materials. The metallic phases obtained after heat treatment are determined and compare in both thermal influenced cases.

Phase Stability and High Temperature Tensile Properties of W doped gamma-TiAl

ABSTRACTTungsten (W) doped γ-TiAl is one of promising alloys among many other proposed TiAl base alloys, for the purpose of structural applications at elevated temperatures. Ingots of W doped γ-TiAl were produced by plasma arc melting, followed by homogenizing heat treatment and isothermal forging to control their microstructures. The phase stability of W doped γ-TiAl has been studied quantitatively, using the specimens quenched from 1273 K. Equilibrium compositions of consisting phases were analyzed by means of EDS analysis in a TEM. An isothermal cross section of the Ti-Al-W ternary phase diagram at 1273K has been proposed based on the experimental observations. Small amounts of W addition (< 1at%) to Ti-48at%Al cause a phase shift from α2+γ to α2+β+γ, which suggests that W is the strongest β stabilizer among transition metals, such as Cr and Mo. Mechanical property measurements of W doped γ-TiAl show that the high temperature tensile strength has been improved by the W addition. Relationships between the microstructures and the mechanical properties of W doped γ-TiAl have been discussed.