Plasticity Enhancement Processes in NiAl and MoSi_2

This paper demonstrates that plasticity enhancement processes previously observed in bcc metalsand associated with the presence of surface films and precipitates or dispersoids are operative in or-dered intermetallic compounds.' Some specific results are given for NiAl-and MoSi_2-basedmaterials.The plasticity of NiAl and related B2 ordered alloys at room temperature during monotonicdeformation can be enhanced by application of surface films such as electroless nickel platings.Sig-nificant effects are also observed during cyclic deformation.The presence of ductile second phasessuch as fcc γ or the ordered phase γ' introduced by alloying also enhances the plasticity of NiAl.MoSi_2 exhibits similar effects of surface films and second phases,but primarily at elevated tempera-tures,T>900℃.In this paper,we illustrate the effects of ZrO_2 surface films deposited near roomtemperature and TiC particulate additions introduced by powder processing techniques.In all cases,the plasticity enhancement is associated with enhanced dislocation generation processes under theconditions of constrained deformation at the film-substrate or precipitate/dispersoid-matrix inter-face of the composite system.

Plasticity Enhancement Processes in NiAl and MoSi_2

This paper demonstrates that plasticity enhancement processes previously observed in bcc metals and associated with the presence of surface films and precipitates or dispersoids are operative in or- dered intermetallic compounds.' Some specific results are given for NiAl-and MoSi_2-based materials.The plasticity of NiAl and related B2 ordered alloys at room temperature during monotonic deformation can be enhanced by application of surface films such as electroless nickel platings.Sig- nificant effects are also observed during cyclic deformation.The presence of ductile second phases such as fcc γ or the ordered phase γ' introduced by alloying also enhances the plasticity of NiAl. MoSi_2 exhibits similar effects of surface films and second phases,but primarily at elevated tempera- tures,T>900℃.In this paper,we illustrate the effects of ZrO_2 surface films deposited near room temperature and TiC particulate additions introduced by powder processing techniques.In all cases, the plasticity enhancement is associated with enhanced dislocation generation processes under the conditions of constrained deformation at the film-substrate or precipitate/dispersoid-matrix inter- face of the composite system.