Tushar Borkar

Laser additive processing of functionally-graded Fe–Si–B–Cu–Nb soft magnetic materials

ABSTRACT Laser additive manufacturing is a novel tool for processing compositionally-graded alloys that are challenging to process via a conventional route. This article discusses a novel combinatorial approach for assessing composition–microstructure–magnetic property relationships, using laser deposited compositionally-graded Fe–Si–B–Nb–Cu alloys (by changing the silicon to boron ratios). The microstructure of Fe–Si–B–Nb–Cu alloys with a lower Si to B ratio consists of dendritic α-Fe3Si grains, with B and Nb partitioning to the inter-dendritic regions, resulting in the formation of Fe3B grains. As the Si/B ratio increases, the (Fe, Nb) enriched eutectic phase was observed along with α-Fe3Si grains; and no Fe3B was observed. These microstructural changes with varying Si/B ratios significantly affect the magnetic properties of these laser-deposited soft magnetic alloys.

Spark Plasma Sintering (SPS) of Carbon Nanotube (CNT) / Graphene Nanoplatelet (GNP)-Nickel Nanocomposites: Structure Property Analysis

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are attractive reinforcements for lightweight and high strength metal matrix composites due to their excellent mechanical and physical properties. The CNT/Ni (DM) nanocomposites exhibiting a tensile yield strength of 350 MPa (about two times that of nickel ∼ 160 MPa) and an elongation to failure ∼ 30%. In contrast, CNT/Ni (MLM) exhibited substantially higher tensile yield strength (∼ 690 MPa) but limited ductility with an elongation to failure ∼ 8%. GNP/Nickel nanocomposites were also processed via DM followed by SPS consolidation. The Ni-1vol%GNP nanocomposite exhibited the best balance of properties in terms of strength and ductility. The enhancement in the tensile strength (i.e. 370 MPa) and substantial ductility (∼ 40%) of Ni-1vol%GNP nanocomposites was achieved due to the combined effects of grain refinement, homogeneous dispersion of GNPs in the nickel matrix, and well-bonded Ni-GNP interface effectively transfers stress across metal-GNP interface during tensile deformation.