THE ROLE OF MICROSTRUCTURE ON STRENGTH AND DUCTILITY OF HOT-EXTRUDED MECHANICALLY ALLOYED NIAL

Mechanical alloying followed by hot extrusion has been used to produce very fine-grained NiAl-based alloys containing oxide dispersoids. The dispersoids affect the progress of recrystallization during hot extrusion and contribute to the preservation of the [110] deformation fiber texture. The [110] texture enables the activation of {110} (100) and {110} [110] slip systems. The occurrence of [100] and [110] slip dislocations satisfies the von Mises criterion for general plasticity and is postulated to contribute to notable room-temperature compressive ductility of the mechanically alloyed (MA) materials. Another factor likely affecting the compressive ductility is the predominant occurrence of low-angle grain boundaries. The attractive dislocation-dispersoid interactions lead to a ductility trough observed at 800 K in the MA materials. The MA NiAl materials are strong at both ambient and elevated temperatures due to fine grain and the presence of dispersoids and interstitial atoms.