Microstructures and fracture behaviors of B-free and B-doped Ir3Nb (L12) intermetallic compounds

The fracture behaviors of the boron-free and boron-doped L12 intermetallic compound Ir3Nb were investigated by compression tests in air and vacuum (5×10−4 Pa). High-temperature differential thermal analysis, X-ray diffraction, and scanning electron microscopy were conducted to characterize the microstructure change by the addition of boron in Ir3Nb. The results reveal that Ir3Nb fractures in intergranular mode in both air and vacuum. Boron doping improves the strength and ductility of doped Ir3Nb, and changes the fracture mode to transgranular. But more boron addition, above 500 wppm for Ir3Nb, causes a low melting temperature Ir–boride phase to form. On the basis of the results the relationship between boron doping, microstructure development, and the fracture behavior of Ir3Nb is discussed.