The precipitation behavior of tantalum (Ta) and NiAl along grain boundaries has been investigated in polycrystalline Fe-28.5Ni-17.5Co-11.5Al-2.5Ta-0.05B (NCATB) (at%) alloy in order to understand their role in limiting its superelastic behavior. It is found that Ta precipitates at grain boundary triple-junctions first, then along grain boundaries, and acts as nuclei for β-NiAl phase formation. Small amounts of boron is also found distributed adjacent to the Ta precipitates. Consequently, the martensitic transformation associated with the superelastic response is promoted along grain boundaries by the Ta and β-NiAl precipitated there. Furthermore, increasing aging temperature facilitates the precipitation of Ta and β-NiAl along grain boundaries. The mean cell width of precipitates along grain boundaries significantly affects the fracture mode and ductility of NCATB specimens. Both the fraction of low-angle boundaries and the intensity of recrystallization texture are significantly increased with increasing reduction in thickness of cold-rolled specimens over 95%, which is effective for the suppression of Ta and β-NiAl formation as their formation occurs primarily on high angle grain boundaries. As a result, the superelastic behavior of the FeNiCoAlTaB alloy is closely linked to the reduction in thickness, which increases the ratio of low angle to high angle boundaries, and hence the propensity for grain boundary failure associated with the grain boundary precipitates and grain boundary initiated martensitic transformation.

研究了钽（Ta）和NiAl在多晶Fe-28.5Ni-17.5Co-11.5Al-2.5Ta-0.05B（NCATB）（at％）合金中沿晶界的沉淀行为，以了解它们在限制合金中的作用。它的超弹性行为。发现Ta首先在晶界三结处析出，然后沿晶界析出，并作为形成β-NiAl相的核。还发现少量硼分布在Ta析出物附近。因此，通过沉积在其中的Ta和β-NiAl沿晶界促进了与超弹性响应相关的马氏体转变。此外，时效温度的升高促进了Ta和β-NiAl沿晶界的析出。沿晶界析出物的平均晶胞宽度会显着影响NCATB试样的断裂模式和延展性。随着冷轧试样厚度的减少，厚度减小超过95％，低角度边界的比例和重结晶织构强度均显着增加，这对于抑制Ta和β-NiAl的形成是有效的，因为它们的形成主要发生在Ta和β-NiAl上。高角度晶界。结果，FeNiCoAlTaB合金的超弹性行为与厚度的减小紧密相关，这增加了低角度与高角度边界的比率，因此，与晶界析出物和晶界相关的晶界破坏的倾向性开始了。马氏体转变。随着冷轧试样厚度的减少，厚度减小超过95％，低角度边界的比例和重结晶织构强度均显着增加，这对于抑制Ta和β-NiAl的形成是有效的，因为它们的形成主要发生在Ta和β-NiAl上。高角度晶界。结果，FeNiCoAlTaB合金的超弹性行为与厚度的减小紧密相关，这增加了低角度与高角度边界的比率，因此，与晶界析出物和晶界相关的晶界破坏的倾向性开始了。马氏体转变。随着冷轧试样厚度的减少，厚度减小超过95％，低角度边界的比例和重结晶织构强度均显着增加，这对于抑制Ta和β-NiAl的形成是有效的，因为它们的形成主要发生在Ta和β-NiAl上。高角度晶界。结果，FeNiCoAlTaB合金的超弹性行为与厚度的减小紧密相关，这增加了低角度与高角度边界的比率，因此，与晶界析出物和晶界相关的晶界破坏的倾向性开始了。马氏体转变。这对于抑制Ta和β-NiAl的形成是有效的，因为它们的形成主要发生在高角度晶界上。结果，FeNiCoAlTaB合金的超弹性行为与厚度的减小紧密相关，这增加了低角度与高角度边界的比率，因此，与晶界析出物和晶界相关的晶界破坏的倾向性开始了。马氏体转变。这对于抑制Ta和β-NiAl的形成是有效的，因为它们的形成主要发生在高角度晶界上。结果，FeNiCoAlTaB合金的超弹性行为与厚度的减小紧密相关，这增加了低角度与高角度边界的比率，因此，与晶界析出物和晶界相关的晶界破坏的倾向性开始了。马氏体转变。