Powder Injection Molding of Cu–Al–Ni Shape Memory Alloy Components: Feedstock Rheology and Sintering Response

Cu–Al–Ni shape memory alloys (SMAs) are promising candidates for engineering applications because of their thermal stability, damping capacity, and relatively low cost compared with Ni–Ti SMAs. Powder injection molding (PIM) is a potential route for producing small and geometrically complex Cu–Al–Ni components; however, its success depends strongly on feedstock rheology, defect-controlled debinding, and suitable sintering response. In this study, 84Cu–12Al–4Ni (wt.%) SMA components were fabricated by PIM using a binder system composed of 65 wt.% paraffin wax, 30 wt.% high-density polyethylene, and 5 wt.% stearic acid. Feedstocks containing 64, 66, and 68 vol.% powder were prepared and rheologically evaluated. The 64 vol.% feedstock showed the most suitable rheological behavior, with favorable flow behavior index, flow activation energy, and general mobility index values. Defect-free green parts were produced by injection molding and subsequently subjected to solvent debinding in n-heptane at 60 ° C for 8 h, followed by thermal debinding at 500 °C for 75 min under Ar. Sintering at 1000 °C for 2.5 h promoted particle bonding and partial consolidation of the Cu–Al–Ni component. FESEM/EDS observations showed elemental interdiffusion together with carbon-rich regions, indicating that further debinding–sintering optimization is required. XRD analysis of the as-sintered component revealed α-Cu/Cu-rich and β/β1 -related phases, suggesting phase development after sintering and furnace cooling.