3D Printing of Aluminum Alloys via Material Extrusion (MEX) Process: Challenges in Developing Acetone-Soluble Binder Systems

Metal material extrusion (MMEX) is a technique to produce a part, characterized by the sequential deposition of material in layers, which is subsequently followed by debinding and sintering to yield fully dense metallic components. The feedstocks, consisting of metal powder combined with a binder system, are essential in determining both the processability and the final attributes of the manufactured parts. In this study, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), contact angle measurement, rheological measurements, printability, and solvent debinding tests were performed for developing a binder system for MMEX of aluminum alloys. Various binder system formulations with polypropylene (PP) as the backbone along with different thermoplastic elastomers (TPEs) as the soluble part were used. During the solvent debinding, two different solvents, cyclohexane and acetone, were evaluated. The results indicated that acetone was ineffective as a solvent for the TPEs used in this study, primarily due to the low solubility of the TPEs in acetone. However, more than 90 vol% of the TPE was removed using cyclohexane as the solvent even at room temperature. Ultimately, the optimized binder formulation for the MMEX process of the aluminum alloys was chosen to consist of polypropylene (PP) as the backbone and thermoplastic elastomer (TPE) soluble in cyclohexane as the primary component. This formulation successfully facilitated all stages of the MMEX process, from shaping to sintering.