Influence of Different Powder Particle Sizes and Binder Systems on the Mechanical and Shape Memory Properties of Metal Injection Moulded NiTi Parts

摘要

Nickel Titanium (NiTi) parts produced by traditional methods (casting, rolling, drawing) show high material cost and poor machining behavior. Metal injection molding (MIM) as a near-net-shape process is attractive for the industrial production of NiTi shape memory components. Two different, prealloyed, gas-atomized NiTi powders (49.55 and 50.85 at.% Ni) were used as starting materials. From the powders, particle fractions with a medium size of 10 μm and 25 μm, respectively, were mixed with two different binder systems. Specimens with tensile test geometry are formed by metal injection molding. After debinding and sintering, the produced parts were characterized by microstructural and chemical analysis. In addition HIP samples are prepared for comparison. Shape memory properties like phase transformation temperatures are determined by DSC measurements. Tensile tests were performed over a wide temperature range to investigate the influence of the resulting stress levels due to the martensite/austenite ratio on the mechanical behavior.