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The deformation behaviours of Ni_3Al alloys with various chemical compositions and subjectedto different heat treatments were in situ observed under SEM. Moreover,in situ observationsof slip trace were supplemented by the direct observation of dislocation arrangements underTEM.In B-doped Ni_3Al alloys it is shown that close to the grain boundary there exists a thinslip transition region,within which slip lines are reoriented or other slip systems are operatedto produce a local strain accommodation and to relax the stress concentration at grain bound-aries.Boron seems to lower the stress for dislocation generation from the grain boundaries orto ease the cross-slip close to the boundaries,and also to increase the number of dislocationsources.However,B-enhenced ductility is seriously affected by stoichiometry,the addition ofa tertiary alloy element and heat treatment,etc..
The deformation behaviors of Ni_3Al alloys with various chemical compositions and subjected to different heat treatments were in situ observed under SEM. Furthermore, in situ observations of slip traces were supplemented by the direct observation of dislocation arrangements under TEM. B-doped Ni_3Al alloys it is shown that close to the grain boundary there exists a thinslip transition region, within which slip lines are reoriented or other slip systems are operated to produce a local strain accommodation and to relax the stress concentration at grain bound-aries. Bouron seems to lower the stress for dislocation generation from the grain boundary orto ease the cross-slip close to the boundaries, and also to increase the number of dislocations resources. However, B-enhenced ductility is seriously affected by stoichiometry, the addition of a tertiary alloy element and heat treatment, etc.