The density,nature of the dislocations and distribution of the domain sizes in cold-deformed Pb-Ca-Sn solid solution were determined by X-ray diffraction profile analysis.The dislocation densities are of the order of ...The density,nature of the dislocations and distribution of the domain sizes in cold-deformed Pb-Ca-Sn solid solution were determined by X-ray diffraction profile analysis.The dislocation densities are of the order of 1010 cm-2.The strain broadening of diffraction profiles was accounted for by dislocation contrast factor.The coherent domain size was determined by the recently developed PM2K software package.Assuming that the domain size distribution is log-normal,the distribution function（median μ and variance σ） was calculated from the size parameters determined from X-ray diffraction profile analysis.展开更多
FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a s...FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a solid solution phase is observed.The density and hardness of the prepared HEAs are improved by Si and Ti additions,compared to FeNiCrCo HEA.The wear rate of the prepared alloys was studied at different loads and the results indicate that the alloys that contain 0.3 wt.%Si and 0.9 wt.%Ti have the lowest wear rates.X-ray diffraction,SEM,and EDX were used to understand the phases,grain sizes,and microstructures in different investigated HEAs.The effects of Si and Ti content on the corrosion behavior and surface morphologies of sintered FeNiCrCoSi_(x) and FeNiCrCoTi_(x) HEAs were studied by immersion in H_(2)SO_(4),HNO_(3),and HCl solutions.Uniform corrosion and localized pitting are observed in different sizes in the corrosive media used.Because of the smaller pit size and the reduced pit density,the FeNiCrCoSi_(0.3) HEA has an excellent microstructure.展开更多
With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precip...With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.展开更多
In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural...In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural modification is on crystallographic texture, and, for aluminium alloys, this may improve the deformability after recrystallization. This work correlated the process variables, thickness reduction per pass(TRP) and velocity ratio between the upper and bottom rolls, with the texture development and the plastic properties after annealing. Finite element(FE) simulations were performed to quantify the influence of the strain components. Experimental data on texture, and plastic anisotropy were analyzed. In the sheet centre a crystallographic rotation of the compression components about the TD(transverse direction) axis was obtained, which yielded the development of {111}//ND(normal direction) texture components. On the surfaces the local variation of the velocity gradients caused an extra rotation component about ND. This yielded the increment of rotated cube components. After annealing the main texture components at the sheet centre were maintained and the texture intensity decreased. The planar anisotropy(△r) was reduced but the normal anisotropy and deep drawability obtained by the Erichsen test were similar for all conditions. The most favourable reduction of △r was obtained at a velocity ratio of 1.5 and TRP of 10%.展开更多
In order to meet the demands of high temperature components in automobile, the microstructure and mechanical properties of several new die-casting AZ91-rare earth (RE) magnesium alloys were studied. The alloys were ch...In order to meet the demands of high temperature components in automobile, the microstructure and mechanical properties of several new die-casting AZ91-rare earth (RE) magnesium alloys were studied. The alloys were characterized by optical microscopy (OM), scan electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), tensile and creep tests. The results show that Ce addition has little effect on the mechanical properties of AZ91 alloy at high temperature, while Y and Nd addition play important role in the improvement of creep resistance. New alloys containing Y or Nd with excellent high temperature performance are selected to produce cylinder head cover of high power diesel engine of Red Flag car and oil pan of Besturn car. The new magnesium alloys with RE addition for die-casting have potential to produce power-train parts, and can greatly decrease weight.展开更多
Crystal structures of nonstoichiometric La(Ni, Sn)5+x (x = 0.1～0.4) alloys prepared by different methods were investigated by using powder X-ray diffraction and Rietveld refinement analysis. Space group of this type ...Crystal structures of nonstoichiometric La(Ni, Sn)5+x (x = 0.1～0.4) alloys prepared by different methods were investigated by using powder X-ray diffraction and Rietveld refinement analysis. Space group of this type of alloys belongs to P6/mmm, in which Sn only occupies the 3g sites. It has been demonstrated that some of the 1a sites of the nonstoichiometric alloy are replaced by the NiNi dumb-bells which have a strong correlation with the anisotropic thermal parameter B33. The preparation methods have an effect on the number of dumb-bells that can substitute the 1a sites. It was found that the annealed alloys have more NiNi dumb-bells in the structure than the rapid solidified and as-cast alloys have while still keep good crystallinity.展开更多
The physical characteristics and microstructure of the fluoride film formed during activation were investigated using SEM,XPS and SAM,and its stability in electroless nickel(EN) bath was analyzed.The effects of the fl...The physical characteristics and microstructure of the fluoride film formed during activation were investigated using SEM,XPS and SAM,and its stability in electroless nickel(EN) bath was analyzed.The effects of the fluoride film on EN deposition were studied additionally.The results show that the fluoride film on magnesium alloys is a kind of porous film composed of MgF2 with thickness of 1.6-3.2 μm.The composition of the activation bath and pretreatment of EN processing have influence on the composition of the fluoride film.The fluoride is stable and dissolves little in EN bath;as a result,the fluoride film can protect magnesium substrate from the corrosion of EN bath.The composition of fluoride determines the initial deposition of EN and part of the fluoride film finally exists as inclusion in EN coating.展开更多
Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined ...Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.展开更多
文摘The density,nature of the dislocations and distribution of the domain sizes in cold-deformed Pb-Ca-Sn solid solution were determined by X-ray diffraction profile analysis.The dislocation densities are of the order of 1010 cm-2.The strain broadening of diffraction profiles was accounted for by dislocation contrast factor.The coherent domain size was determined by the recently developed PM2K software package.Assuming that the domain size distribution is log-normal,the distribution function（median μ and variance σ） was calculated from the size parameters determined from X-ray diffraction profile analysis.
文摘FeNiCrCoSi_(x) and FeNiCrCoTi_(x)(x=0,0.3,0.6,and 0.9 wt.%)high entropy alloys(HEAs)were prepared via the powder metallurgy technique.A homogenous distribution of the elements in all alloys due to the formation of a solid solution phase is observed.The density and hardness of the prepared HEAs are improved by Si and Ti additions,compared to FeNiCrCo HEA.The wear rate of the prepared alloys was studied at different loads and the results indicate that the alloys that contain 0.3 wt.%Si and 0.9 wt.%Ti have the lowest wear rates.X-ray diffraction,SEM,and EDX were used to understand the phases,grain sizes,and microstructures in different investigated HEAs.The effects of Si and Ti content on the corrosion behavior and surface morphologies of sintered FeNiCrCoSi_(x) and FeNiCrCoTi_(x) HEAs were studied by immersion in H_(2)SO_(4),HNO_(3),and HCl solutions.Uniform corrosion and localized pitting are observed in different sizes in the corrosive media used.Because of the smaller pit size and the reduced pit density,the FeNiCrCoSi_(0.3) HEA has an excellent microstructure.
文摘With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.
基金supported by Sao Paulo State Research Foundation (FAPESP 2016/10997-0)by CAPES–Brazil
文摘In asymmetric rolling(ASR) the circumferential velocities of the working rolls are different. This yields a complex deformation mode with shear, compression and rigid body rotation components. The main microstructural modification is on crystallographic texture, and, for aluminium alloys, this may improve the deformability after recrystallization. This work correlated the process variables, thickness reduction per pass(TRP) and velocity ratio between the upper and bottom rolls, with the texture development and the plastic properties after annealing. Finite element(FE) simulations were performed to quantify the influence of the strain components. Experimental data on texture, and plastic anisotropy were analyzed. In the sheet centre a crystallographic rotation of the compression components about the TD(transverse direction) axis was obtained, which yielded the development of {111}//ND(normal direction) texture components. On the surfaces the local variation of the velocity gradients caused an extra rotation component about ND. This yielded the increment of rotated cube components. After annealing the main texture components at the sheet centre were maintained and the texture intensity decreased. The planar anisotropy(△r) was reduced but the normal anisotropy and deep drawability obtained by the Erichsen test were similar for all conditions. The most favourable reduction of △r was obtained at a velocity ratio of 1.5 and TRP of 10%.
基金Project(2006AA03Z520) supported by the National High-tech Research and Development Program of China
文摘In order to meet the demands of high temperature components in automobile, the microstructure and mechanical properties of several new die-casting AZ91-rare earth (RE) magnesium alloys were studied. The alloys were characterized by optical microscopy (OM), scan electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), tensile and creep tests. The results show that Ce addition has little effect on the mechanical properties of AZ91 alloy at high temperature, while Y and Nd addition play important role in the improvement of creep resistance. New alloys containing Y or Nd with excellent high temperature performance are selected to produce cylinder head cover of high power diesel engine of Red Flag car and oil pan of Besturn car. The new magnesium alloys with RE addition for die-casting have potential to produce power-train parts, and can greatly decrease weight.
基金This work was supported by the National Natural Science Foundation of China (50071052) and National Natural Science Key Foundation of China (50131040)
文摘Crystal structures of nonstoichiometric La(Ni, Sn)5+x (x = 0.1～0.4) alloys prepared by different methods were investigated by using powder X-ray diffraction and Rietveld refinement analysis. Space group of this type of alloys belongs to P6/mmm, in which Sn only occupies the 3g sites. It has been demonstrated that some of the 1a sites of the nonstoichiometric alloy are replaced by the NiNi dumb-bells which have a strong correlation with the anisotropic thermal parameter B33. The preparation methods have an effect on the number of dumb-bells that can substitute the 1a sites. It was found that the annealed alloys have more NiNi dumb-bells in the structure than the rapid solidified and as-cast alloys have while still keep good crystallinity.
基金Project(50101007) supported by the National Science Natural Foundation of China
文摘The physical characteristics and microstructure of the fluoride film formed during activation were investigated using SEM,XPS and SAM,and its stability in electroless nickel(EN) bath was analyzed.The effects of the fluoride film on EN deposition were studied additionally.The results show that the fluoride film on magnesium alloys is a kind of porous film composed of MgF2 with thickness of 1.6-3.2 μm.The composition of the activation bath and pretreatment of EN processing have influence on the composition of the fluoride film.The fluoride is stable and dissolves little in EN bath;as a result,the fluoride film can protect magnesium substrate from the corrosion of EN bath.The composition of fluoride determines the initial deposition of EN and part of the fluoride film finally exists as inclusion in EN coating.
基金supported by the National Natural Science Foundation of China (Nos. 51674166, U1902220)the National Key R&D Program of China (No. 2021YFB3701303)。
文摘Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.
