Sintering is a high-temperature process used to transform loosely bound powder aggregates into near net-shaped, dense objects with controlled amounts of porosity. In many sintering applications, external constraints can prevent a powder aggregate from densifying in one or more directions. Under these constrained sintering conditions, internal stresses can develop in the sintering material, and in extreme cases, these stresses can grow so large that they tear the powder aggregate apart. This fracture process, referred to as sinter-cracking, degrades product quality, lowers yield, and proves highly undesirable in manufacturing processes. This award supports fundamental research to understand the sinter-cracking phenomenon. The goal of this research is to clarify why this cracking occurs, with a view toward identifying processing strategies for suppressing fracture during constrained sintering. By relating material properties, geometric factors, and process variables to the growth of sinter-cracks, this research will guide materials engineers towards processing and manufacturing parameters to prevent catastrophic sinter-cracking. This new scientific knowledge will have important applications in the powder processing industry, potentially benefiting a range of manufacturing sectors, particularly those making use of new 3D printing technologies, including the aerospace, automotive, and energy sectors.
This research project aims to understand the ductile-to-brittle transition in sintered materials. 3D printing will be used to independently vary important geometric features during sintering experiments such as the size of the starter crack, the specimen thickness, and the initial length of the uncracked ligament. By coupling experiments on these 3D printed specimens with discrete element method simulations of sinter-cracking, continuum descriptions of stresses and strains will be linked with particle-scale phenomena occurring at the crack tip to develop a multi-scale, physics-based understanding of sinter-cracking and the causes of the ductile-brittle transition.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
