Metal Injection Moulding of Superelastic TiNi Parts

J Eric Bidaux,François Aeby,Hervé Girard,Lionel Reynard,Efrain Carreño-Morelli,Alexandra Amherd Hidalgo,Jacques Chevallier,Jean Charles Giachetto,Mikel Rodriguez-Arbaizar

doi:10.4028/www.scientific.net/kem.704.173

Abstract

TiNi shape-memory properties are successfully used today for the fabrication of various technical devices. The limited machinability and high cost of TiNi encourage the use of near-net shape production techniques such as metal injection moulding. In this work TiNi alloys tensile test specimens are produced by metal injection moulding from pre-alloyed powders. A binder based on a mixture of polyethylene, paraffin wax and stearic acid is used. Parts with a density of about 96.6% of theoretical density are obtained. Scanning electron microscopy coupled with EDX measurements reveals a microstructure consisting of a TiNi matrix with small Ti4Ni2Ox and TiC inclusions. DSC and X-ray diffraction observations indicate the presence of additional Ni4Ti3 precipitates. The parts exhibit full superelasticity at room temperature even for strains of up to 4%, without the need for additional thermal post-treatments. Ultimate tensile strengths up to 980 MPa are obtained.

Highlights

Discovered in 1962 by Buehler and Wang, TiNi alloys remain today the commercially most important shape-memory alloys [1,2]
The limited machinability and high cost of TiNi encourage the use of near-net shape production techniques such as metal injection moulding
TiNi parts with densities of about 96.6% of the theoretical density have been successfully produced by metal injection moulding

Summary

Introduction

Discovered in 1962 by Buehler and Wang, TiNi alloys remain today the commercially most important shape-memory alloys [1,2]. In this work TiNi alloys tensile test specimens are produced by metal injection moulding from pre-alloyed powders. DSC and X-ray diffraction observations indicate the presence of additional Ni4Ti3 precipitates.

Results

Conclusion