To study the formation and transformation mechanism of long-period stacked ordered(LPSO)structures,a systematic atomic scale analysis was conducted for the structural evolution of long-period stacked ordered(LPSO)stru...To study the formation and transformation mechanism of long-period stacked ordered(LPSO)structures,a systematic atomic scale analysis was conducted for the structural evolution of long-period stacked ordered(LPSO)structures in the Mg-Gd-Y-Zn-Zr alloy annealed at 300℃~500℃.Various types of metastable LPSO building block clusters were found to exist in alloy structures at different temperatures,which precipitate during the solidification and homogenization process.The stability of Zn/Y clusters is explained by the first principles of density functional theory.The LPSO structure is distinguished by the arrangement of its different Zn/Y enriched LPSO structural units,which comprises local fcc stacking sequences upon a tightly packed plane.The presence of solute atoms causes local lattice distortion,thereby enabling the rearrangement of Mg atoms in the different configurations in the local lattice,and local HCP-FCC transitions occur between Mg and Zn atoms occupying the nearest neighbor positions.This finding indicates that LPSO structures can generate necessary Schockley partial dislocations on specific slip surfaces,providing direct evidence of the transition from 18R to 14H.Growth of the LPSO,devoid of any defects and non-coherent interfaces,was observed separately from other precipitated phases.As a result,the precipitation sequence of LPSO in the solidification stage was as follows:Zn/Ycluster+Mg layers→various metastable LPSO building block clusters→18R/24R LPSO;whereas the precipitation sequence of LPSO during homogenization treatment was observed to be as follows:18R LPSO→various metastable LPSO building block clusters→14H LPSO.Of these,14H LPSO was found to be the most thermodynamically stable structure.展开更多
Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-ro...Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.展开更多
用力学性能、电阻率、X-射线衍射和 TEM 技术研究了冷变形对 Cu 9 Ni 6 Sn 0.3 Ce 合金spinodal 分解动力学的影响。冷变形后直接时效合金表明强化过程加强。根据位错理论的讨论,冷变形合金中加速强化的特征,可以归结为加速了 spinodal...用力学性能、电阻率、X-射线衍射和 TEM 技术研究了冷变形对 Cu 9 Ni 6 Sn 0.3 Ce 合金spinodal 分解动力学的影响。冷变形后直接时效合金表明强化过程加强。根据位错理论的讨论,冷变形合金中加速强化的特征,可以归结为加速了 spinodal 分解动力学过程。展开更多
It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there ar...It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there are two satellites (sidebands) around X ray main diffraction peak. With the wavelength and asymmetric factor α y of rectangle wave of the distribution of concentration introduced, the amplitude of modulation wave appearing along some crysallographic direction can be expressed clearly in the form of a sum of several diffraction wave vectors in the reciprocal space, and the diffracted intensity can be obtained. The X ray diffraction angle of sidebands strongly depends on the distribution of the wavelength. Fig.1b gives the simulated X ray diffraction profiles. It shows that when we fix the average modulated wavelength and change the distribution of wavelength, the angle difference between the satellite and main diffraction peak varies correspondingly. The simulated diffraction profiles are in good agreement with experimental results [1] (Fig.1a). The more diffuse the distribution of wavelength is, the nearer the sidebands are to main peak, and vice versa. In addition, the intensity and position of satellite are obviously restricted by the asymmetric factor of wave shape. Any lattice wave propagating in crystal can be resolved along coordinate axes. On the basis of the principle of superposition, all compositions of the lattice wave have diffraction profiles of themselves. Add two diffraction patterns perpendicular to each other on the reciprocal plane which is normal to the projected direction, we get the simulated TEM diffraction pattern of spinodal decomposition. Fig.2a is the TEM pattern by Kubo H [2] , Fig.2b and 2c are the simulated TEM patterns by Kubo H [2] and Khachaturyan A G [3] respectively. Our simulated TEM pattern (Fig.2d) is in good agreement with Fig.2a.展开更多
Copper alloyed with various compositions of nickel and tin were cast into molds under argon atmosphere.The cast rods were homogenized,solution heat treated,followed by aging for different time duration.The specimens w...Copper alloyed with various compositions of nickel and tin were cast into molds under argon atmosphere.The cast rods were homogenized,solution heat treated,followed by aging for different time duration.The specimens were characterized for microstructure and tested for microhardness and wear rate.A hybrid model with a linear function and radial basis function was developed to analyze the influence of nickel,tin,and aging time on the microhardness and tribological behavior of copper-nickel-sin alloy system.The results indicate that increase in the composition of nickel and tin increases the microhardness and decreases the wear rate of the alloy.The increase in the concentration of nickel and tin decreases the peak aging time of the alloy system.展开更多
基金financially funded by Natural Science Basic Research Program of Shaanxi(grant number 2022JM-239)Key Research and Development Project of Shaanxi Provincial(grant number 2021LLRH-05–08)。
文摘To study the formation and transformation mechanism of long-period stacked ordered(LPSO)structures,a systematic atomic scale analysis was conducted for the structural evolution of long-period stacked ordered(LPSO)structures in the Mg-Gd-Y-Zn-Zr alloy annealed at 300℃~500℃.Various types of metastable LPSO building block clusters were found to exist in alloy structures at different temperatures,which precipitate during the solidification and homogenization process.The stability of Zn/Y clusters is explained by the first principles of density functional theory.The LPSO structure is distinguished by the arrangement of its different Zn/Y enriched LPSO structural units,which comprises local fcc stacking sequences upon a tightly packed plane.The presence of solute atoms causes local lattice distortion,thereby enabling the rearrangement of Mg atoms in the different configurations in the local lattice,and local HCP-FCC transitions occur between Mg and Zn atoms occupying the nearest neighbor positions.This finding indicates that LPSO structures can generate necessary Schockley partial dislocations on specific slip surfaces,providing direct evidence of the transition from 18R to 14H.Growth of the LPSO,devoid of any defects and non-coherent interfaces,was observed separately from other precipitated phases.As a result,the precipitation sequence of LPSO in the solidification stage was as follows:Zn/Ycluster+Mg layers→various metastable LPSO building block clusters→18R/24R LPSO;whereas the precipitation sequence of LPSO during homogenization treatment was observed to be as follows:18R LPSO→various metastable LPSO building block clusters→14H LPSO.Of these,14H LPSO was found to be the most thermodynamically stable structure.
文摘Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.
文摘It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there are two satellites (sidebands) around X ray main diffraction peak. With the wavelength and asymmetric factor α y of rectangle wave of the distribution of concentration introduced, the amplitude of modulation wave appearing along some crysallographic direction can be expressed clearly in the form of a sum of several diffraction wave vectors in the reciprocal space, and the diffracted intensity can be obtained. The X ray diffraction angle of sidebands strongly depends on the distribution of the wavelength. Fig.1b gives the simulated X ray diffraction profiles. It shows that when we fix the average modulated wavelength and change the distribution of wavelength, the angle difference between the satellite and main diffraction peak varies correspondingly. The simulated diffraction profiles are in good agreement with experimental results [1] (Fig.1a). The more diffuse the distribution of wavelength is, the nearer the sidebands are to main peak, and vice versa. In addition, the intensity and position of satellite are obviously restricted by the asymmetric factor of wave shape. Any lattice wave propagating in crystal can be resolved along coordinate axes. On the basis of the principle of superposition, all compositions of the lattice wave have diffraction profiles of themselves. Add two diffraction patterns perpendicular to each other on the reciprocal plane which is normal to the projected direction, we get the simulated TEM diffraction pattern of spinodal decomposition. Fig.2a is the TEM pattern by Kubo H [2] , Fig.2b and 2c are the simulated TEM patterns by Kubo H [2] and Khachaturyan A G [3] respectively. Our simulated TEM pattern (Fig.2d) is in good agreement with Fig.2a.
文摘Copper alloyed with various compositions of nickel and tin were cast into molds under argon atmosphere.The cast rods were homogenized,solution heat treated,followed by aging for different time duration.The specimens were characterized for microstructure and tested for microhardness and wear rate.A hybrid model with a linear function and radial basis function was developed to analyze the influence of nickel,tin,and aging time on the microhardness and tribological behavior of copper-nickel-sin alloy system.The results indicate that increase in the composition of nickel and tin increases the microhardness and decreases the wear rate of the alloy.The increase in the concentration of nickel and tin decreases the peak aging time of the alloy system.
