We have investigated the effects of B impurities on the structure and mechanical properties of NiA1 intermetallics by using a first-principles pseudopotential total-energy method, based on the density functional theor...We have investigated the effects of B impurities on the structure and mechanical properties of NiA1 intermetallics by using a first-principles pseudopotential total-energy method, based on the density functional theory with a generalized gradient approximation. We found that the impurity B atoms can either replace Ni atoms or Al atoms or both, depending on the surround- ing environment. We demonstrated that the presence of B will cause an increase in brittleness and a decrease in the ductility of NiAI for the Al-substitutional case, while causing an increase in the ductility of NiAl for the Ni-subtitutional case, based on the calculated elastic constants and the empirical criterions. This indicates that the effects of B impurities on the mechanical prop- erties of NiAl intermetallics are quite composition-dependent.展开更多
A multiphase alloy NiAI-28Cr-5.8Mo-0.2Hf was directionally solidified in Ar atmosphere in an Al2O3-SiC2 mold by standard Bridgman method. The fracture toughness and tensile properties at 980℃ as well as tensile creep...A multiphase alloy NiAI-28Cr-5.8Mo-0.2Hf was directionally solidified in Ar atmosphere in an Al2O3-SiC2 mold by standard Bridgman method. The fracture toughness and tensile properties at 980℃ as well as tensile creep at 1050℃ were studied. It was found that the strength of the present alloy is higher than that of many NiAI-based alloy and the stress exponent n for creep is about 6.69. Then the possible strengthening mechanism and creep mechanism are also discussed.展开更多
The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obta...The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obtained from the computation show that NiAl lacks a metastable disordered structure intrinsically, and has the stable ordered B2 phase,which are consistent with experimental results.展开更多
基金supported by the Basic Research Project of High Education (Grant No. ZXH2009C004)the Foundation of CAUC (Grant No. 09QD06X)
文摘We have investigated the effects of B impurities on the structure and mechanical properties of NiA1 intermetallics by using a first-principles pseudopotential total-energy method, based on the density functional theory with a generalized gradient approximation. We found that the impurity B atoms can either replace Ni atoms or Al atoms or both, depending on the surround- ing environment. We demonstrated that the presence of B will cause an increase in brittleness and a decrease in the ductility of NiAI for the Al-substitutional case, while causing an increase in the ductility of NiAl for the Ni-subtitutional case, based on the calculated elastic constants and the empirical criterions. This indicates that the effects of B impurities on the mechanical prop- erties of NiAl intermetallics are quite composition-dependent.
文摘A multiphase alloy NiAI-28Cr-5.8Mo-0.2Hf was directionally solidified in Ar atmosphere in an Al2O3-SiC2 mold by standard Bridgman method. The fracture toughness and tensile properties at 980℃ as well as tensile creep at 1050℃ were studied. It was found that the strength of the present alloy is higher than that of many NiAI-based alloy and the stress exponent n for creep is about 6.69. Then the possible strengthening mechanism and creep mechanism are also discussed.
文摘The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obtained from the computation show that NiAl lacks a metastable disordered structure intrinsically, and has the stable ordered B2 phase,which are consistent with experimental results.
