Enhancement of ductility in Fe-Co based alloys by substitution of Pd

We investigated the relationship between the microstructure and mechanical properties of the ternary Co50Fe50−xPdx alloys with different Pd content. Co50Fe45Pd5, Co50Fe40Pd10 and Co50Fe35Pd15 alloys annealed at 873 K were composed of the α'-matrix having a B2 structure with a high degree of order and two kinds of Fe-Co-Pd precipitates with L10 and L12 structures, which formed at the grain boundaries and in the grain interior. The 0.2% proof stress, tensile strength, hardness and elongation were increased by substituting Pd for Fe in Co-Fe-Pd alloy. It is noteworthy that the Co50Fe40Pd10 alloy had a high tensile strength of 1293 MPa and high total elongation of 12% on average. The significant improvement in the ductility of the Co50Fe40Pd10 alloy is attributed to the ductile Fe-Co-Pd phase that precipitates at the grain boundaries and in the α′-grain interior. The ductile precipitates suppressed the intergranular and cleavage fracture. The increase in strength of Co50Fe50−xPdx alloys is likely to come from both the precipitation hardening and the grain refinement of the α′-matrix.