Processing behavior of nanocrystalline NiAl during milling, sintering and mechanical loading and interpretation of its intergranular fracture

• Milling of Ni–Al powders resulted in obtaining of nanocrystalline NiAl.
• SEM, TEM and XRD results confirmed microstrain/dislocations on microstructure.
• Sintering of nanocrystalline NiAl by HP resulted in grain growths toward ultrafine.
• Ultrafine grain microstructure resulted in improvement of the mechanical properties.
• Formation of voids/cracks at grain boundaries caused intergranular fracture.

Processing behavior of Ni and Al powders during milling, sintering and compression loading was evaluated using SEM, TEM and XRD-Rietveld’s refinement analysis techniques. Nanocrystalline NiAl intermetallic along with microstrain and dislocations on its microstructure was obtained after milling. Sintering of nanocrystalline powders at 1180 °C under a pressure of 48 MPa for 1 h time by hot press technique resulted in grain growths toward ultrafine along with decreasing of microstrain and dislocations on microstructure. Obtaining a microstructure of ultrafine grained NiAl resulted in improvement of mechanical properties. Intergranular fracture was characterized by the coupling of dislocations at grain boundaries that caused to formation of voids/cracks with progressive loading.

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