Microstructure evolution and magnetic properties of metastable immiscible Cu-Fe alloy with micro-alloying B element

Highlights: • Microstructure evolution and solidification behavior of Cu-20Fe-xB were elucidated. • Introducing B element brings about obviously change in solidification microstructure. • Phase diagram calculation indicates a stable miscibility gap forms by the B addition. • The B addition remarkably enhances the magnetic properties of Cu-Fe alloy. • Significant improvement on Ms (~32.3%) was achieved for Cu-20Fe-0.3B alloy. -- Abstract: In the present study, metastable immiscible Cu-20Fe-xB alloys with different B addition content were systematically investigated. Experimental results demonstrated that the introduction of micro-alloying B element results in significant change in the solidification microstructure. It was found the volume fraction of phase-separated Fe-rich spherulite increases with increasing B addition content accompanied with an increase in the average size, which experimentally confirms that the liquid-liquid phase separation is further enhanced as B addition increases. In addition, statistical result on scaled size distribution of the phase-separated Fe-rich spherulite indicated that both the concentrated location for the first and second peak are shifted to a larger size scale with increasing B addition. Phase diagram calculation confirms that a stable miscibility gap comes into being by introducing B element, and the length of miscibility gap for Cu-20Fe alloy is obviously enlarged with increasing B addition amount. This should be responsible for such above-mentioned experimental results. Besides, the magnetic properties of Cu-20Fe alloy can be obviously enhanced with B addition. For Cu-20Fe-0.3B alloy, the saturated magnetization is 41.74 emu/g, which is 32.3% significantly higher than that of the original Cu-20Fe alloy (31.56 emu/g). It is anticipated that the present study provides a feasible method by tailoring the micro-alloying B content for immiscible Cu-Fe alloy thus offering desired magnetic properties.