Yuye Wu

Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys

Dual-phase (Fe83Ga17)100−xTbx alloys with 0 ≤ x ≤ 1 were synthesized by arc melting and homogenization treatment. The microstructures and the corresponding mechanical properties were systematically investigated. The chemical composition of the body centered cubic matrix is Fe83Ga17. The monoclinic second phase was composed of meltable precipitates with approximate composition Fe57Ga33Tb10. The nano-hardness of matrix and precipitates were 2.55 ± 0.17 GPa and 6.81 ± 1.03 GPa, respectively. Both the ultimate tensile strength (UTS) and fracture strain (ε) of the alloys were improved by the precipitates for x ≤ 0.2 alloys, but the strain decreases significantly at higher values of x. As potential structural-functional materials, the best mechanical properties obtained were a UTS of 595 ± 10 MPa and an ε of 3.5 ± 0.1%, four-fold and seven-fold improvements compared with the un-doped alloy. The mechanism for these anomalous changes of mechanical properties was attributed to the dispersed precipitates and semi-coherent interfaces, which serve as strong obstacles to dislocation motion and reduce the stress concentration at the grain boundaries. A sizeable improvement of magnetostriction induced by the precipitates in the range 0 ≤ x ≤ 0.2 was discovered and an optimal value of 150 ± 5 ppm is found, over three times higher than that of the un-doped alloy.

Influence of cooling rate on magneto-structural transition and magnetocaloric effect of Ni30Cu8Co12Mn37Ga13 alloy

The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied. Difference in atomic order is induced by changing cooling rates, where ordered phase is obtained in the furnace cooled (FC) sample while disordered phase is reserved in the water quenched (WQ) sample. The coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic order. Giant magnetic entropy change (ΔSmag) derived from magnetic field induced martensitic transformation is confirmed for both samples, and can be remarkably enhanced by the atomic ordering. The largest ΔSmag of 20.9 J/(kg · K) is obtained at 307.5 K under 5 T in the FC sample.

Improved magneostriction and mechanical properties in dual-phase FeGa single crystal

ABSTRACT Single-phase Fe81Ga19 and dual-phase (Fe0.81Ga0.19)99.95Tb0.05 single crystals with perfect orientation were prepared by directional solidification technology. The performance of the dual-phase single crystal (SC) can achieve 399 ppm in magnetostriction and 10.2% in tensile fracture strain, which are, respectively, 28% and 5 times larger than those in single-phase Fe81Ga19 SC. The slight solid solution of Tb and dispersive distributed Tb-rich particles in dual-phase SC, respectively, lead to the improvement in magnetostriction and ductility. This dual-phase SC can become the candidate for new-generation magnetostrictive materials combining significant advantages in both structural and functional properties. Impact statement This dual-phase (Fe0.81Ga0.19)99.95Tb0.05 single crystal combining large magnetostriction and excellent mechanical properties can be new-generation magnetostrictive materials which can satisfy the application requirement in structural and functional properties. GRAPHICAL ABSTRACT