Effect of feeding material shape on microstructures and mechanical properties in friction rolling additive manufacturing

Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing method capable of accommodating a wide range of material forms. However, there is a lack of comprehensive research on the optimal feedstock form. Thus, this study investigated the influence of feedstock shape on material formation, microstructure, and mechanical properties. The results revealed that irrespective of whether a strip or wire was used, the plasticized material flowed through a thin plastic flow channel (approximately 112 μm) between the tool head and the feedstock. Wire feedstock resulted in greater deformation and more significant grain refinement than strip feedstock, with grain refinements of 95 % and 81 %, respectively. Additionally, gaps between multiple wires were filled with plasticized material, forming a dense and defect-free mixing zone. Moreover, the tensile performances of the deposited samples obtained from wire and strip feedstocks exhibited no significant differences, measuring 143.9 MPa and 144.5 MPa, respectively. Numerical simulations were employed to elucidate the underlying mechanism of the temperature field and material flow behavior when strips and wires were used as feed materials. The findings of this study are anticipated to serve as a reference for selecting feedstock forms for FRAM.