Microstructure, Plastic Deformation and Mechanical Properties of MechanicallyAlloyed NiAl and NiAl Based Alloys

摘要

Nickel aluminide (NiAl) and NiAl based alloys have been produced by mechanicalalloys (MA) and hot extrusion, resulting in material which was fully dense, with a homogeneous, bimodal distribution of oxide paricles and with a fine grain size of less than 1 micrometers. Mechanical properties of the MA alloys have been studied by compression testing from room temperature to 1300 K in air. Yield strengths ranged from 1453 MPa to 32 MPa depending on material and test temperature. The MA materials showed a considerable compressive ductility at room temperature (greater than 11.5%) without any microcracking being observed. A ductility minimum was observed at 800K in all MA materials which is deduced to be due to dynamic strain aging. The effects of microstructure on the mechanical properties are discussed. Transmission electron microscopy has been carried out in order to characterize deformation mechanisms. < 001 > slip was found to be predominant but a strong evidence of < 011 > slip was also gathered. The occurrence of < 001 > and < 011 > slip vectors satisfies general requirement for plasticity and explains significant room temperature ductility of MA NiAl. Cast NiAl has been also investigated for comparison with the MA materials. It exhibited a poor ductility (2.3%) and only < 001 > dislocations were observed. < 001 > slip provides only three independent slip systems and the number of independent slip systems is insufficient. The differences between cast and MA NiAl are discussed.