A novel approach hybridizing lithography-pressureless sintering additive manufacturing to go beyond the critical casting size limit of Fe-based bulk metallic glass

Fe-based bulk metallic glass (BMG) is an amorphous metallic alloy that of high potential to be applied in biomedical devices, automotive and aerospace, sports equipment, etc. due to its attractive mechanical, physical and chemical properties. However, Fe-based BMG has low glass forming ability (GFA) and high tendency to crack during solidification, restricting its critical casting size to few millimeters. Alternatively, different fabrication techniques were proposed to overcome the size limitations problem such as Metal Additive Manufacturing (MAM) techniques. MAM are promising to exceed the size limitations; however, the fusion-based techniques such as, (SLM) lead to the crystallization of the amorphous structure after few layers. Sinter-based MAM is another approach that allows 3D printing at low temperatures followed by sintering. Thus, a 3-steps MAM approach is proposed using lithography-based 3D printing, followed by debinding and pressureless sintering, relying only on heat to consolidate the material into a denser and monolithic object. The samples produced achieved an average densification of ~ 65% and showed amorphous-crystalline composite structure (~ 83–90% amorphous content) with signs of initial diffusion between the particles. The three-point bending test confirmed initial stages of sintering with modulus of rupture up to 7.9 MPa. These results demonstrated the feasibility of the proposed approach for additive manufacturing of Fe-based BMG. In the future, the sintering parameters (heating ramp, soaking temperature and time) should be further investigated to achieve comparable mechanical strength to as-cast Fe-based BMG.