Solvent Debinding of Cu-Al-Ni Shape Memory Alloy Micro-Components Produced by Micro-Powder Injection Molding

The escalating demand for the high-volume manufacturing of precisely detailed and small-scale parts has become increasingly pronounced over the past few years. In this context, micro-powder injection molding (µPIM), an advanced adaptation of the powder injection molding (PIM) technique, has proven to be a cost-effective and technically sophisticated method for the precise shaping and mass production of micro-scale metallic and ceramic parts. µPIM is a potentially efficacious process for the fabrication of micro-sized Cu-Al-Ni shape memory alloy (SMA) components. However, debinding remains challenging for micro-sized components, regardless of materials, because of their tendency toward cracking and dimensional distortion. This study involved the formulation of a 68 vol. % powder-loaded Cu-Al-Ni feedstock through the mixing of a Cu-Al-Ni powder mixture with a binder system, composed of paraffin wax (PW), high-density polyethylene (HDPE), and stearic acid (SA), at an elevated temperature of 150°C maintained for 1 hour period to ensure feedstock homogeneity. Green micro-components of Cu-Al-Ni SMA were produced through micro-injection molding by employing controlled process conditions comprising an injection pressure of 10 bar, an injection duration of 6 s, a mold temperature of 145°C, and a melt temperature of 180 °C. Following a solvent debinding procedure at 60°C for 1 hour, 74.4% of the PW and SA soluble binders were effectively removed from the green micro-component without inducing any defects or cracking in the component. The open channels formed in the solvent debound parts assist in the expulsion of the HDPE binder through thermal debinding phase.