Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The res...Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2（Ti, Hf, Nb, W） alloy consists of four phases： NiAl, ？？Cr solid solution, Cr2Nb and Ni2Al（Ti, Hf）. The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56？？0-3 s-1, due to the existence of Cr2Nb and Ni2Al（Ti, Hf） phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr（Mo, W） solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation： ε=0.898 σ8.47exp[-615/（RT）].展开更多
The microstructure, compressive properties at different temperatures and hardness of NiAl-Cr（Mo）-Nb alloy prepared by injection casting were investigated. Compared with the conventionally-cast alloy, the injection-c...The microstructure, compressive properties at different temperatures and hardness of NiAl-Cr（Mo）-Nb alloy prepared by injection casting were investigated. Compared with the conventionally-cast alloy, the injection-cast alloy exhibits a fine microstructure, i.e. the fine eutectic cell and interlamellar spacing as well as fine primary NiAl phase and NbCr2-type Laves phase due to the high cooling rate. In addition, the area fraction of eutectic cell increases due to the narrow intercellular zone. The Vickers hardness of injection-cast alloy is markedly enhanced. The ductility and strength at room temperature are increased by 88% and 30% compared with those of conventionally-cast alloy respectively. However, the high-temperature strength of injection-cast alloy is not improved markedly. The elevated temperature compression deformation behavior can be properly described by power-law equations.展开更多
The influence of strain rate and temperature on the tensile behavior of as-cast and HIPed NiAI-9Mo eutectic alloy was investigated in the temperature range of 700-950℃ and over a strain rate range from 2.08×10-4...The influence of strain rate and temperature on the tensile behavior of as-cast and HIPed NiAI-9Mo eutectic alloy was investigated in the temperature range of 700-950℃ and over a strain rate range from 2.08×10-4 s-1 to 2.08×10-2 s-1. The results indicate that HIP process causes an enhancement in ductility and a decrease in ultimate tensile strength (UTS), yield strength (YS), average strain hardening rate as well as a drop in brittle to ductile transition temperature(BDTT) under the same condition. It is noticed that the BDTT of as-cast NiAI-9Mo is more dependent on strain rate than that of HIPed one. The brittle to ductile transition process of the alloy is related to a sharp drop in strain hardening rate. Regardless of strain rate, the fracture morphology changes from cleavage in NiAl phase and debonding along NiAI/Mo interface below the BDTT to microvoid coalescence above BDTT. The apparent activation energy of the BDT of HIPed and as-cast material are calculated to be 327 and 263 kJ/mol, respectively, suggesting that the mechanism is associated with lattice diffusion in NiAl phase.展开更多
The structure and morphology of as-cast Fe-13wt-% Mo-0.8wt-% C alloy have been ob- served under SEM and TEM.Few δ-eutectoid but certain minor eutectics appear in the core of dendrites of the alloy.The eutectic carbid...The structure and morphology of as-cast Fe-13wt-% Mo-0.8wt-% C alloy have been ob- served under SEM and TEM.Few δ-eutectoid but certain minor eutectics appear in the core of dendrites of the alloy.The eutectic carbide is found as skeleton M_6C while the eutectoid carbide as rodlet M_6C.展开更多
以Cu片为基体,在氯化胆碱-乙二醇深共熔体系中电沉积制备Ni-Mo合金镀层,借助EIS,SEM,EDS和XRD等手段分析Ni-Mo合金镀层沉积动力学,探讨极化电位对Ni-Mo合金镀层电催化析氢性能的影响规律。结果表明:随着极化电位的增加,Ni-Mo合金镀层经...以Cu片为基体,在氯化胆碱-乙二醇深共熔体系中电沉积制备Ni-Mo合金镀层,借助EIS,SEM,EDS和XRD等手段分析Ni-Mo合金镀层沉积动力学,探讨极化电位对Ni-Mo合金镀层电催化析氢性能的影响规律。结果表明:随着极化电位的增加,Ni-Mo合金镀层经历从纳米Ni,Ni+MoO_(2)(MoO_(2)Ni_(4))和Ni_(4)Mo成分演变过程,说明电位驱动是影响Ni-Mo合金镀层成分变化的重要原因。当极化电位为-1.4 V vs Ag时,Ni-Mo-1.4合金镀层具有优良的析氢催化活性和催化稳定性,其在10 mA·cm^(-2)电流密度下的析氢过电位仅为51 mV,Tafel斜率为48.7 mV·dec^(-1),循环催化1000周次后在100 mA·cm^(-2)电流密度下的析氢过电位下降较小(Δη100=11 mV)。展开更多
基金Project supported by Aerospace Science and Technology Innovation Fund of China
文摘Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2（Ti, Hf, Nb, W） alloy consists of four phases： NiAl, ？？Cr solid solution, Cr2Nb and Ni2Al（Ti, Hf）. The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56？？0-3 s-1, due to the existence of Cr2Nb and Ni2Al（Ti, Hf） phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr（Mo, W） solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation： ε=0.898 σ8.47exp[-615/（RT）].
文摘The microstructure, compressive properties at different temperatures and hardness of NiAl-Cr（Mo）-Nb alloy prepared by injection casting were investigated. Compared with the conventionally-cast alloy, the injection-cast alloy exhibits a fine microstructure, i.e. the fine eutectic cell and interlamellar spacing as well as fine primary NiAl phase and NbCr2-type Laves phase due to the high cooling rate. In addition, the area fraction of eutectic cell increases due to the narrow intercellular zone. The Vickers hardness of injection-cast alloy is markedly enhanced. The ductility and strength at room temperature are increased by 88% and 30% compared with those of conventionally-cast alloy respectively. However, the high-temperature strength of injection-cast alloy is not improved markedly. The elevated temperature compression deformation behavior can be properly described by power-law equations.
基金The authors gratefully acknowledge the National Natural Science Foundation of China for its financial support under the contract No.59895152.
文摘The influence of strain rate and temperature on the tensile behavior of as-cast and HIPed NiAI-9Mo eutectic alloy was investigated in the temperature range of 700-950℃ and over a strain rate range from 2.08×10-4 s-1 to 2.08×10-2 s-1. The results indicate that HIP process causes an enhancement in ductility and a decrease in ultimate tensile strength (UTS), yield strength (YS), average strain hardening rate as well as a drop in brittle to ductile transition temperature(BDTT) under the same condition. It is noticed that the BDTT of as-cast NiAI-9Mo is more dependent on strain rate than that of HIPed one. The brittle to ductile transition process of the alloy is related to a sharp drop in strain hardening rate. Regardless of strain rate, the fracture morphology changes from cleavage in NiAl phase and debonding along NiAI/Mo interface below the BDTT to microvoid coalescence above BDTT. The apparent activation energy of the BDT of HIPed and as-cast material are calculated to be 327 and 263 kJ/mol, respectively, suggesting that the mechanism is associated with lattice diffusion in NiAl phase.
文摘The structure and morphology of as-cast Fe-13wt-% Mo-0.8wt-% C alloy have been ob- served under SEM and TEM.Few δ-eutectoid but certain minor eutectics appear in the core of dendrites of the alloy.The eutectic carbide is found as skeleton M_6C while the eutectoid carbide as rodlet M_6C.
文摘以Cu片为基体,在氯化胆碱-乙二醇深共熔体系中电沉积制备Ni-Mo合金镀层,借助EIS,SEM,EDS和XRD等手段分析Ni-Mo合金镀层沉积动力学,探讨极化电位对Ni-Mo合金镀层电催化析氢性能的影响规律。结果表明:随着极化电位的增加,Ni-Mo合金镀层经历从纳米Ni,Ni+MoO_(2)(MoO_(2)Ni_(4))和Ni_(4)Mo成分演变过程,说明电位驱动是影响Ni-Mo合金镀层成分变化的重要原因。当极化电位为-1.4 V vs Ag时,Ni-Mo-1.4合金镀层具有优良的析氢催化活性和催化稳定性,其在10 mA·cm^(-2)电流密度下的析氢过电位仅为51 mV,Tafel斜率为48.7 mV·dec^(-1),循环催化1000周次后在100 mA·cm^(-2)电流密度下的析氢过电位下降较小(Δη100=11 mV)。
