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

Dual-phase (Fe83Ga17)(100-x) Tb-x 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 (epsilon) 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 e 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.