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.