The corrosion behavior of typical high-strength aluminum alloy LY12 was studied by accelerated corrosion tests of cyclic wet-dry-immersion containing media of NaHSO3 and NaCl to simulate the corrosion process in diffe...The corrosion behavior of typical high-strength aluminum alloy LY12 was studied by accelerated corrosion tests of cyclic wet-dry-immersion containing media of NaHSO3 and NaCl to simulate the corrosion process in different atmosphere environment, and the corrosion mechanism was also discussed. The main experimental techniques include mass loss, morphological check, analysis of corrosion products and electrochemical measurement. The result shows that the mass loss of LY12, with or without cladding, has linear relationship with test time in the three kinds of chemical media, 0.02 mol/L NaHSO3, 0.006 mol/L NaCl and 0.02 mol/L NaHSO3+0.006 mol/L NaCl, respectively. A layer of cladding on high-strength aluminum alloy can raise evidently the resistance of atmospheric corrosion. Cl- can promote pitting generation on the oxide film of LY12 when HOS 3-exists, LY12 can react much intensely with HOS3- derived from anions.展开更多
The corrosion morphologies of aged magnesium alloy AZ80 were investigated by immersion corrosion tests, scanning electron microscopy (SEM), electrochemical measurement. The T5 heat treatment was carried out in a vac...The corrosion morphologies of aged magnesium alloy AZ80 were investigated by immersion corrosion tests, scanning electron microscopy (SEM), electrochemical measurement. The T5 heat treatment was carried out in a vacuum furnace, holding for 16 h at 177℃, and then cooling in air. The results showed intergranular corrosion (IGC) occurred as an aged AZ80 sample was immersed in 3.5 wt pct NaCI aqueous solution for 1 h and the narrow path attack progressed predominantly along the bulk β phase in the grain boundaries or took place in the eutectic areas. IGC was attributed to the network distribution of β phase along the grain boundaries, the depleted aluminium in the precipitation areas and the breakdown potential.展开更多
Anew anodizing process, which does not contain chromate but can improve the corrosion resistance of magnesium alloys significantly, was developed using a microarc power supply. Surface morphology was observed and the ...Anew anodizing process, which does not contain chromate but can improve the corrosion resistance of magnesium alloys significantly, was developed using a microarc power supply. Surface morphology was observed and the coating was compact and ceramic-like. In addition, the corrosion resistance of samples before and after anodization by the new process and a method in US Patent 5470664 was compared by potentiodymaic polarization curves, electrochemical impedance spectroscopy (EIS) and salt spray test. The results show that the anodization can improve the corrosion resistance of magnesium alloy. The samples obtained by the new process and the method mentioned in the US Patent 5470664 achieve 9 and 7 rates after 336 h salt spray test, respectively.展开更多
Through performing the tensile tests with different strain rates in 3.5 wt.%NaCl solution,the stress corrosion cracking(SCC)behavior and the effect of strain rate on the SCC susceptibility of an extruded Mg-7%Gd-5%Y-1...Through performing the tensile tests with different strain rates in 3.5 wt.%NaCl solution,the stress corrosion cracking(SCC)behavior and the effect of strain rate on the SCC susceptibility of an extruded Mg-7%Gd-5%Y-1%Nd-0.5%Zr(EW75)alloy have been investigated.Results demonstrate that the alloy is susceptible to SCC when the strain rate is lower than 5×10^(−6) s^(−1).At the strain rate of 1×10^(−6) s^(−1),the SCC susceptibility index(I_(SCC))is 0.96 and the elongation-to-failure(ε_(f))is only 0.11%.Fractography indicates that the brittle quasi-cleavage feature is very obvious and become more pronounced with decreasing the strain rate.Further analysis confirms that the cracking mode is predominantly transgranular,but the partial intergranular cracking at some localized area can also occur.Meanwhile,it seems that the crack propagation path is unrelated to the existing phase particles.展开更多
The corrosion behavior of WE54 magnesium alloy was investigated in 3.5%NaCl aqueous solution. The electrochemical study shows that the value of corrosion potential of WE54 magnesium was -1.8V(vs SCE). In the initial s...The corrosion behavior of WE54 magnesium alloy was investigated in 3.5%NaCl aqueous solution. The electrochemical study shows that the value of corrosion potential of WE54 magnesium was -1.8V(vs SCE). In the initial stage of immersion, a kind of visible thin film, which has the appearance of artificial conversion coating by microscopy observation, formed on the surface of WE54 alloy. Through the comparison of corrosion behavior between WE54 and AZ91D, it is shown that the value of corrosion potential of WE54 is approximately 200 mV lower than that of AZ91D, and the corrosion rate of WE54 was one order smaller than that of AZ91D. After 72 h constant immersion and corrosion products removal, deeper grooves along grain boundaries was revealed but lighter corrosion was apparent on the matrix of WE54 alloy. As far as AZ91D alloy was concerned, severe localized corrosion was dominant and network-bone-like structure was remained.展开更多
Corrosion of magnesium alloys is an important issue for their applications in automobile and aerospace industry. pH values as a function of time in two types of simulated occluded corrosion cells(OCC) for magnesium al...Corrosion of magnesium alloys is an important issue for their applications in automobile and aerospace industry. pH values as a function of time in two types of simulated occluded corrosion cells(OCC) for magnesium alloys AZ80 and AM60 were measured. The influence of mass ratio of solution to material or liquid to solid ratio(L/S ratio),initial pH value and chemical compositions of solutions on pH value in OCC was discussed. The experimental results show that pH value for magnesium alloys increases gradually or rapidly in Occ,depending on L/S ratio,initial pH value of solution and chloride ions concentration etc,and then reaches up to 10.5-10.6 and finally stabilizes at the level. The onset in the pH value time curve corresponds to the precipitate of magnesium hydroxide according to the theoretical calculation.展开更多
The serrated phenomena of the quasicrystalline phase reinforced Mg-4%Li-6%Zn-1.2%Y alloy after the extrusion,solid solution treatment and aged treatment have been investigated at different temperatures.The result show...The serrated phenomena of the quasicrystalline phase reinforced Mg-4%Li-6%Zn-1.2%Y alloy after the extrusion,solid solution treatment and aged treatment have been investigated at different temperatures.The result shows that when the temperature is above 100℃,the serrated phenomenon becomes weak and all the serrated amplitudes are lower than 1 MPa.Among them,the serrated amplitude of samples in aged condition is the lowest and the value is only 0.1-0.2 MPa.The underneath mechanism for the lower plastic instability at higher temperature(≥100℃)can be ascribed to the weak pining effect of solute atoms on the movement of dislocation and release of the pile-up dislocations.展开更多
The dispersion state of nano-TiO2 particles was studied by using transmission electron microscopy (TEM)and Fourier transform infrared spectroscopy (FT-IR). Nanoparticles can be fully dispersed by specific hyperdis...The dispersion state of nano-TiO2 particles was studied by using transmission electron microscopy (TEM)and Fourier transform infrared spectroscopy (FT-IR). Nanoparticles can be fully dispersed by specific hyperdispersant. The improvement of nano-TiO2 in thermal behavior and flame retardation of acrylic polymer and fire-resistant coating was investigated by differential thermal analysis (DTA), thermogravimetry (TG)and fire-resistant time test. It is demonstrated that nano-TiO2 is helpful for enhancing the thermal stability,anti-oxidation and fire-resistant properties of acrylic polymer and fire-resistant coating.展开更多
In order to investigate the distribution of Cu and Mg, and the effect of Cu on the microstructure of steels, manganese steels containing various Cu contents were annealed at 1260, 1100 and 1000℃, respectively, for I ...In order to investigate the distribution of Cu and Mg, and the effect of Cu on the microstructure of steels, manganese steels containing various Cu contents were annealed at 1260, 1100 and 1000℃, respectively, for I h and subsequently cooled to room temperature in the furnace to simulate the pre-rolling anneal. The results indicate that Cu is not microscopically segregated in the annealed steels. The scanning electron microscopy (SEM) observation shows that the main microstructure consist of ferrite and pearlite; the percentage of pearlite in the steels increases with increasing Cu content. The grain size reduces with the decrease of the annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that Cu content in pearlite is higher than that in ferrite, demonstrating that the microstructure-segregation of Cu occurred. However, the cast specimens show that Cu content in MnS and S-rich phases is high. In addition, Cu of 0.2%-0.4% could improve the distribution of MnS and S-rich inclusions. The optimal Cu content in steels and the optimal annealing temperature between 1100-1200℃ were determined.展开更多
Fine-grained magnesium alloys strengthened by quasicrystalline particles were easily developed by thermomechanical process for Mg-Zn-Y-Zr alloys. The microstructure evolution of Mg-Zn-Y-Zr alloys hot rolled with diffe...Fine-grained magnesium alloys strengthened by quasicrystalline particles were easily developed by thermomechanical process for Mg-Zn-Y-Zr alloys. The microstructure evolution of Mg-Zn-Y-Zr alloys hot rolled with different reductions at different temperatures was studied. Tensile tests and fracture observation were carried out to study the mechanical properties of this alloy. The thin magnesium sheets hot rolled at 380℃exhibit better combination of high strength and ductility than that hot rolled at lower temperature. The results show that the grains become equiaxed and uniform as compared with those of the extruded materials because of recrystallization and repeated heating between rolling passes. It is also found that with the increasing rolling temperature and strain theⅠ-phase particles become much smaller and are homogeneously distributed in the matrix, which enhances both strength and ductility.展开更多
The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and mo...The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.展开更多
For a long time, chromate incorporated conversion coatings have been drawn special attention in corrosion protection of aircraft-used aluminum alloys. However, ever-increasing environmental pressures requires that non...For a long time, chromate incorporated conversion coatings have been drawn special attention in corrosion protection of aircraft-used aluminum alloys. However, ever-increasing environmental pressures requires that non-chromate conversion coatings be developed because of the detrimental carcinogenic effects of the chromate compounds. In recent years, the sol-gel coatings doped with inhibitors were developed to replace chromate conversion coatings, and showed real promise; A sol-gel coating was prepared and its anti-corrosion behavior was investigated using the potentiodynamic scanning (PDS) and the electrochemical impedance spectroscopy (EIS). It is found that the sol-gel coating obtained by the hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) is prone to form defects if cured at the room temperature, whereas if cured at a higher temperature (100℃), these flaws can be avoided. Furthermore, it can be seen that addition of anti-foam agents and surfactants will reduce the faults if cured at the room temperature. Effects of the corrosion inhibitors, CeCl3 and mercaptobenzothiazole (MBT), in the sol-gel coatings on 2024-T3 aluminum alloy were also investigated. Results show that the corrosion resistance of the sol-gel coatings containing CeCl3 proves to be better than that of the pure and MBT added sol-gel coatings by the electrochemical methods.展开更多
The deformation behaviour of an AZE (Mg-3Al-1Zn-0.1RE) alloy at temperature between 393 and 453 K was investigated by uniaxial compression tests carried out at initial strain rate values of 1×10-4, 5×10-4 ...The deformation behaviour of an AZE (Mg-3Al-1Zn-0.1RE) alloy at temperature between 393 and 453 K was investigated by uniaxial compression tests carried out at initial strain rate values of 1×10-4, 5×10-4 and 1×10-3 s-1 in air. The results show that serrated flow occurs at the strain rate of 10-4 s-1 under all test temperatures and 5×10-4 s-1 at 453 K. The mechanism of serrated flow was proposed, which is mainly attributed to the interaction of dislocations to the precipitates.展开更多
In this work, the influence of element RE on the microstructures and mechanical properties of the hot extuded Mg-3Al-1Zn-xRE alloys (with element RE content of 0.05, 0.1 and 0.2 wt pct) has been investigated and com...In this work, the influence of element RE on the microstructures and mechanical properties of the hot extuded Mg-3Al-1Zn-xRE alloys (with element RE content of 0.05, 0.1 and 0.2 wt pct) has been investigated and compared. It was found that RE can bring about precipitations phase that is identified as Al11RE3 by X-ray diffraction and transmission electron microscopy (TEM). The grain sizes would not be refined after adding RE element. Al11RE3 phase would increase strength and decrease the ductility. The addition of RE element affects dynamic recrystallized process and even reorientation of recrystallized grains. The results showed that the mechanical properties of AZ31+RE alloy are affected by combination of Al atoms, Mn atoms, Al11RE3 phase and grains orientation. It is important to consider the ratio of RE/Al when designing new Mg-Al-RE alloys.展开更多
High-cycle fatigue (HCF) behavior of as-forged-T5 Mg-Zn-Y-Zr wrought alloy with stress-ratio R=-1 at ambient environment was presented. The relationship between the maximum stress and the number of cycles to failure w...High-cycle fatigue (HCF) behavior of as-forged-T5 Mg-Zn-Y-Zr wrought alloy with stress-ratio R=-1 at ambient environment was presented. The relationship between the maximum stress and the number of cycles to failure was constructed. The results show that the fatigue strength at 107 cycles of the as-forged alloy in T5 state is higher than that of the alloy in T4 state. However, in T6 state, the fatigue strength at 107 cycles is higher than those of the alloys in both T5 and T4 states.展开更多
The mechanical properties of LA40 magnesium alloy were investigated under compression at room temperature. In the applied strain rate range from 1.33×10-4s-1 to 6.66×10-4s-1,this alloy shows positive strain ...The mechanical properties of LA40 magnesium alloy were investigated under compression at room temperature. In the applied strain rate range from 1.33×10-4s-1 to 6.66×10-4s-1,this alloy shows positive strain rate sensitivity (SRS). Most importantly, the Portevin-Le Chatelier(PLC) effect which is an interesting and dominant feature in tensile tests disappears under compressive conditions. Only one twinning system is activated under tensile deformation, while at least two twinning modes are operative during compression. Additionally, the effect of dynamic strain aging (DSA), and the main mechanism for the onset of PLC phenomenon during tension, will be weakened because the strengthened obstructing influence of twins on solute atoms and the disappearance of PLC is inevitable.展开更多
In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These ...In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These steels are annealed at 1 260℃, 1 100 ℃ and 1 000℃ respectively for one hour and followed by furnace cooling to room temperature to simulate the heat treatment before the rolling process. The results show that Cu did not obviously segregate in annealed steels. The scanning electron microscope (SEM) observation show that the main microstruetures in Cu-bearing steel are ferrite and pearlite; The volume fraction of pearlite in steel increase with increasing Cu content. The grain size reduces with the decrease of annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that the Cu content in pearlite is higher than that in ferrite, which means that the microstructure-segregatian of Cu exists. However, the cast specimens show that Cu content in MnS and S-rich phase is very high, and Cu changed the distribution of/vinS in steel. In addition, the optimal Cu content in steel between 0.2%-0.4% and the optimal annealing temperature between 1 100-1 200℃are determined by the economical and practical principles.展开更多
In this review paper, the research progress on corrosion behavior of hexagonal close-packed(HCP) singular phase, body cubic-centered(BCC) singular phase and(HCP + BCC) duplex-structured Mg–Li alloys has been summariz...In this review paper, the research progress on corrosion behavior of hexagonal close-packed(HCP) singular phase, body cubic-centered(BCC) singular phase and(HCP + BCC) duplex-structured Mg–Li alloys has been summarized and reviewed, and the future trend about the studies on corrosion behavior of Mg–Li-based alloys and possible solving methods for the improvement in corrosion resistance are discussed also.展开更多
Through investigating the corrosion behavior of an as-extruded Mg-3wt%gAl-lwt%Zn (AZ31) alloy in a simulated physiological fluid of Hank's solution, it demonstrates that the corrosion process was depen- dent on the...Through investigating the corrosion behavior of an as-extruded Mg-3wt%gAl-lwt%Zn (AZ31) alloy in a simulated physiological fluid of Hank's solution, it demonstrates that the corrosion process was depen- dent on the immersion time. Further analyses revealed that the highest corrosion resistance could be obtained at 24 h due to the formation of a compact layer of corrosion products on the sample surface. With increasing the immersion time to up to 48 h, the thickness of surface films increased gradually but obvious de-bonding of such film from the substrate could take place, resulting in a certain resilience of the overall corrosion resistance.展开更多
基金Project(50499331) supported by the National Natural Science Foundation of China
文摘The corrosion behavior of typical high-strength aluminum alloy LY12 was studied by accelerated corrosion tests of cyclic wet-dry-immersion containing media of NaHSO3 and NaCl to simulate the corrosion process in different atmosphere environment, and the corrosion mechanism was also discussed. The main experimental techniques include mass loss, morphological check, analysis of corrosion products and electrochemical measurement. The result shows that the mass loss of LY12, with or without cladding, has linear relationship with test time in the three kinds of chemical media, 0.02 mol/L NaHSO3, 0.006 mol/L NaCl and 0.02 mol/L NaHSO3+0.006 mol/L NaCl, respectively. A layer of cladding on high-strength aluminum alloy can raise evidently the resistance of atmospheric corrosion. Cl- can promote pitting generation on the oxide film of LY12 when HOS 3-exists, LY12 can react much intensely with HOS3- derived from anions.
基金the National HiTech R. & D. Program under grant No. 2001AA331050 Key Natural Science Foundation of Chongqing Science and Technology Commission under grant No. 200413A4002 Science & Technology Research Project of Chongqing Education Commission under grant No. KJ050604.
文摘The corrosion morphologies of aged magnesium alloy AZ80 were investigated by immersion corrosion tests, scanning electron microscopy (SEM), electrochemical measurement. The T5 heat treatment was carried out in a vacuum furnace, holding for 16 h at 177℃, and then cooling in air. The results showed intergranular corrosion (IGC) occurred as an aged AZ80 sample was immersed in 3.5 wt pct NaCI aqueous solution for 1 h and the narrow path attack progressed predominantly along the bulk β phase in the grain boundaries or took place in the eutectic areas. IGC was attributed to the network distribution of β phase along the grain boundaries, the depleted aluminium in the precipitation areas and the breakdown potential.
文摘Anew anodizing process, which does not contain chromate but can improve the corrosion resistance of magnesium alloys significantly, was developed using a microarc power supply. Surface morphology was observed and the coating was compact and ceramic-like. In addition, the corrosion resistance of samples before and after anodization by the new process and a method in US Patent 5470664 was compared by potentiodymaic polarization curves, electrochemical impedance spectroscopy (EIS) and salt spray test. The results show that the anodization can improve the corrosion resistance of magnesium alloy. The samples obtained by the new process and the method mentioned in the US Patent 5470664 achieve 9 and 7 rates after 336 h salt spray test, respectively.
基金This work was supported by the National Natural Science Foundation of China projects under Grant Nos.51171192,51271183 and 51301172,the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205 and the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS).
文摘Through performing the tensile tests with different strain rates in 3.5 wt.%NaCl solution,the stress corrosion cracking(SCC)behavior and the effect of strain rate on the SCC susceptibility of an extruded Mg-7%Gd-5%Y-1%Nd-0.5%Zr(EW75)alloy have been investigated.Results demonstrate that the alloy is susceptible to SCC when the strain rate is lower than 5×10^(−6) s^(−1).At the strain rate of 1×10^(−6) s^(−1),the SCC susceptibility index(I_(SCC))is 0.96 and the elongation-to-failure(ε_(f))is only 0.11%.Fractography indicates that the brittle quasi-cleavage feature is very obvious and become more pronounced with decreasing the strain rate.Further analysis confirms that the cracking mode is predominantly transgranular,but the partial intergranular cracking at some localized area can also occur.Meanwhile,it seems that the crack propagation path is unrelated to the existing phase particles.
基金Project(50574086) supported by the National Natural Science Foundation of China
文摘The corrosion behavior of WE54 magnesium alloy was investigated in 3.5%NaCl aqueous solution. The electrochemical study shows that the value of corrosion potential of WE54 magnesium was -1.8V(vs SCE). In the initial stage of immersion, a kind of visible thin film, which has the appearance of artificial conversion coating by microscopy observation, formed on the surface of WE54 alloy. Through the comparison of corrosion behavior between WE54 and AZ91D, it is shown that the value of corrosion potential of WE54 is approximately 200 mV lower than that of AZ91D, and the corrosion rate of WE54 was one order smaller than that of AZ91D. After 72 h constant immersion and corrosion products removal, deeper grooves along grain boundaries was revealed but lighter corrosion was apparent on the matrix of WE54 alloy. As far as AZ91D alloy was concerned, severe localized corrosion was dominant and network-bone-like structure was remained.
基金Projects (200413BA4002, 8655) supported by the Natural Science Foundation of Chongqing Municipal Science Commission, ChinaProject (KJ050604) supported by the Technology Commission and the Science and Technology foundation of Chongqing Municipal Education Commission, China
文摘Corrosion of magnesium alloys is an important issue for their applications in automobile and aerospace industry. pH values as a function of time in two types of simulated occluded corrosion cells(OCC) for magnesium alloys AZ80 and AM60 were measured. The influence of mass ratio of solution to material or liquid to solid ratio(L/S ratio),initial pH value and chemical compositions of solutions on pH value in OCC was discussed. The experimental results show that pH value for magnesium alloys increases gradually or rapidly in Occ,depending on L/S ratio,initial pH value of solution and chloride ions concentration etc,and then reaches up to 10.5-10.6 and finally stabilizes at the level. The onset in the pH value time curve corresponds to the precipitate of magnesium hydroxide according to the theoretical calculation.
基金This work was supported by the National Natural Science Foundation of China projects under Grant Nos.51171192,51271183 and 51301172the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205 and the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences.
文摘The serrated phenomena of the quasicrystalline phase reinforced Mg-4%Li-6%Zn-1.2%Y alloy after the extrusion,solid solution treatment and aged treatment have been investigated at different temperatures.The result shows that when the temperature is above 100℃,the serrated phenomenon becomes weak and all the serrated amplitudes are lower than 1 MPa.Among them,the serrated amplitude of samples in aged condition is the lowest and the value is only 0.1-0.2 MPa.The underneath mechanism for the lower plastic instability at higher temperature(≥100℃)can be ascribed to the weak pining effect of solute atoms on the movement of dislocation and release of the pile-up dislocations.
文摘The dispersion state of nano-TiO2 particles was studied by using transmission electron microscopy (TEM)and Fourier transform infrared spectroscopy (FT-IR). Nanoparticles can be fully dispersed by specific hyperdispersant. The improvement of nano-TiO2 in thermal behavior and flame retardation of acrylic polymer and fire-resistant coating was investigated by differential thermal analysis (DTA), thermogravimetry (TG)and fire-resistant time test. It is demonstrated that nano-TiO2 is helpful for enhancing the thermal stability,anti-oxidation and fire-resistant properties of acrylic polymer and fire-resistant coating.
基金the Major Program of National Natural Science Foundation of China (No. 50499336) National Basic Research Program of China (No. 2004CB619101).
文摘In order to investigate the distribution of Cu and Mg, and the effect of Cu on the microstructure of steels, manganese steels containing various Cu contents were annealed at 1260, 1100 and 1000℃, respectively, for I h and subsequently cooled to room temperature in the furnace to simulate the pre-rolling anneal. The results indicate that Cu is not microscopically segregated in the annealed steels. The scanning electron microscopy (SEM) observation shows that the main microstructure consist of ferrite and pearlite; the percentage of pearlite in the steels increases with increasing Cu content. The grain size reduces with the decrease of the annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that Cu content in pearlite is higher than that in ferrite, demonstrating that the microstructure-segregation of Cu occurred. However, the cast specimens show that Cu content in MnS and S-rich phases is high. In addition, Cu of 0.2%-0.4% could improve the distribution of MnS and S-rich inclusions. The optimal Cu content in steels and the optimal annealing temperature between 1100-1200℃ were determined.
基金Projects(20373072, 20473091) supported by the National Natural Science Foundation of China
文摘Fine-grained magnesium alloys strengthened by quasicrystalline particles were easily developed by thermomechanical process for Mg-Zn-Y-Zr alloys. The microstructure evolution of Mg-Zn-Y-Zr alloys hot rolled with different reductions at different temperatures was studied. Tensile tests and fracture observation were carried out to study the mechanical properties of this alloy. The thin magnesium sheets hot rolled at 380℃exhibit better combination of high strength and ductility than that hot rolled at lower temperature. The results show that the grains become equiaxed and uniform as compared with those of the extruded materials because of recrystallization and repeated heating between rolling passes. It is also found that with the increasing rolling temperature and strain theⅠ-phase particles become much smaller and are homogeneously distributed in the matrix, which enhances both strength and ductility.
基金Projects(CSTC2009AB4008)supported by Key Technologies R&D Program and Natural Science Foundation of Chongqing Science and Technology Commission,ChinaProject(KJ100808,KJ08065)supported by Science and Technology Research Fund of Chongqing Municipal Education Commission,China
文摘The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.
基金National Natural Science Fundation of China (50499334)
文摘For a long time, chromate incorporated conversion coatings have been drawn special attention in corrosion protection of aircraft-used aluminum alloys. However, ever-increasing environmental pressures requires that non-chromate conversion coatings be developed because of the detrimental carcinogenic effects of the chromate compounds. In recent years, the sol-gel coatings doped with inhibitors were developed to replace chromate conversion coatings, and showed real promise; A sol-gel coating was prepared and its anti-corrosion behavior was investigated using the potentiodynamic scanning (PDS) and the electrochemical impedance spectroscopy (EIS). It is found that the sol-gel coating obtained by the hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS) is prone to form defects if cured at the room temperature, whereas if cured at a higher temperature (100℃), these flaws can be avoided. Furthermore, it can be seen that addition of anti-foam agents and surfactants will reduce the faults if cured at the room temperature. Effects of the corrosion inhibitors, CeCl3 and mercaptobenzothiazole (MBT), in the sol-gel coatings on 2024-T3 aluminum alloy were also investigated. Results show that the corrosion resistance of the sol-gel coatings containing CeCl3 proves to be better than that of the pure and MBT added sol-gel coatings by the electrochemical methods.
基金supported by the National Naturral Science Foundation of China under grant No.50431020the National Major Basic Research Program of China("973 Program") under grant No.2007CB613704
文摘The deformation behaviour of an AZE (Mg-3Al-1Zn-0.1RE) alloy at temperature between 393 and 453 K was investigated by uniaxial compression tests carried out at initial strain rate values of 1×10-4, 5×10-4 and 1×10-3 s-1 in air. The results show that serrated flow occurs at the strain rate of 10-4 s-1 under all test temperatures and 5×10-4 s-1 at 453 K. The mechanism of serrated flow was proposed, which is mainly attributed to the interaction of dislocations to the precipitates.
基金supported by the National Natural Science Fundation of China (NSFC) under grant Nos.50431020National Basic Research Program of China(973 Program) project under grant No.2007CB613704
文摘In this work, the influence of element RE on the microstructures and mechanical properties of the hot extuded Mg-3Al-1Zn-xRE alloys (with element RE content of 0.05, 0.1 and 0.2 wt pct) has been investigated and compared. It was found that RE can bring about precipitations phase that is identified as Al11RE3 by X-ray diffraction and transmission electron microscopy (TEM). The grain sizes would not be refined after adding RE element. Al11RE3 phase would increase strength and decrease the ductility. The addition of RE element affects dynamic recrystallized process and even reorientation of recrystallized grains. The results showed that the mechanical properties of AZ31+RE alloy are affected by combination of Al atoms, Mn atoms, Al11RE3 phase and grains orientation. It is important to consider the ratio of RE/Al when designing new Mg-Al-RE alloys.
文摘High-cycle fatigue (HCF) behavior of as-forged-T5 Mg-Zn-Y-Zr wrought alloy with stress-ratio R=-1 at ambient environment was presented. The relationship between the maximum stress and the number of cycles to failure was constructed. The results show that the fatigue strength at 107 cycles of the as-forged alloy in T5 state is higher than that of the alloy in T4 state. However, in T6 state, the fatigue strength at 107 cycles is higher than those of the alloys in both T5 and T4 states.
基金Project (50371089) supported by the National Natural Science Foundation of China
文摘The mechanical properties of LA40 magnesium alloy were investigated under compression at room temperature. In the applied strain rate range from 1.33×10-4s-1 to 6.66×10-4s-1,this alloy shows positive strain rate sensitivity (SRS). Most importantly, the Portevin-Le Chatelier(PLC) effect which is an interesting and dominant feature in tensile tests disappears under compressive conditions. Only one twinning system is activated under tensile deformation, while at least two twinning modes are operative during compression. Additionally, the effect of dynamic strain aging (DSA), and the main mechanism for the onset of PLC phenomenon during tension, will be weakened because the strengthened obstructing influence of twins on solute atoms and the disappearance of PLC is inevitable.
基金This project is supported by National Natural Science Foundation of China (No.50499336)National Basic Research Program of China (973 Program, No.2004CB619101).
文摘In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These steels are annealed at 1 260℃, 1 100 ℃ and 1 000℃ respectively for one hour and followed by furnace cooling to room temperature to simulate the heat treatment before the rolling process. The results show that Cu did not obviously segregate in annealed steels. The scanning electron microscope (SEM) observation show that the main microstruetures in Cu-bearing steel are ferrite and pearlite; The volume fraction of pearlite in steel increase with increasing Cu content. The grain size reduces with the decrease of annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that the Cu content in pearlite is higher than that in ferrite, which means that the microstructure-segregatian of Cu exists. However, the cast specimens show that Cu content in MnS and S-rich phase is very high, and Cu changed the distribution of/vinS in steel. In addition, the optimal Cu content in steel between 0.2%-0.4% and the optimal annealing temperature between 1 100-1 200℃are determined by the economical and practical principles.
基金supported by the National Key Research and Development Program of China (Nos. 2017YFB0702001 and 2016YFB0301105)the National Natural Science Foundation of China (Nos. 51701129 and 51871211)the postdoctoral start fund of Shenyang Ligong University (No. 105000100006)
文摘In this review paper, the research progress on corrosion behavior of hexagonal close-packed(HCP) singular phase, body cubic-centered(BCC) singular phase and(HCP + BCC) duplex-structured Mg–Li alloys has been summarized and reviewed, and the future trend about the studies on corrosion behavior of Mg–Li-based alloys and possible solving methods for the improvement in corrosion resistance are discussed also.
基金supported by the National Key Research and Development Program of China project(Grant No.2016YFB0301105)the Strategic New Industry Development Special Foundation of Shenzhen(No.JCYJ20170306141749970)+3 种基金the National Natural Science Foundation of China(Grant Nos.51701129,51271183 and 51301172)the National Basic Research Program of China("973 Program",Grant No.2013CB632205)the Innovation Fund of Institute of Metal Research(IMR)Chinese Academy of Sciences(CAS)
文摘Through investigating the corrosion behavior of an as-extruded Mg-3wt%gAl-lwt%Zn (AZ31) alloy in a simulated physiological fluid of Hank's solution, it demonstrates that the corrosion process was depen- dent on the immersion time. Further analyses revealed that the highest corrosion resistance could be obtained at 24 h due to the formation of a compact layer of corrosion products on the sample surface. With increasing the immersion time to up to 48 h, the thickness of surface films increased gradually but obvious de-bonding of such film from the substrate could take place, resulting in a certain resilience of the overall corrosion resistance.