Microstructure and mechanical properties of Ni3Al fabricated by thermal explosion and hot extrusion

The dense Ni₃Al with different boron and chromium addition was fabricated by the thermal explosion and hot extrusion (TE/HE) technology. Microstructure examination showed that Ni₃Al contained fine grain structure (200 nm to 10 μm). Analysis of X-ray spectra as well as transmission electron microscopy studies revealed that three phases present in all alloys: γ-Ni, Ni₃Al and dispersoids of Al₂O₃. With the addition of B, β-NiAl phase and twinned Ni₃Al formed, but in the B and Cr doped alloy, Cr rich phase and a spot of Cr₇Ni₃ particles with stacking faults inside were observed. In addition, dislocations with high density existed in all alloys. The mechanical test showed that the B and Cr addition resulted in significant improvement in mechanical properties, and TE/HE synthesized Ni₃Al alloy owned more excellent mechanical properties, compared with the one synthesized by combustion.