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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