The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phas...The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.展开更多
The as-cast Mg-3Zn-0.4Ca alloy shows a great potential to be used in biomedical applications due to its composition,mechanical properties and biodegradability.Zn and Ca appear naturally in the organism accomplishing v...The as-cast Mg-3Zn-0.4Ca alloy shows a great potential to be used in biomedical applications due to its composition,mechanical properties and biodegradability.Zn and Ca appear naturally in the organism accomplishing vital functions.The alloy consists of an a-Mg matrix and a eutectic composed of a-Mg4-Ca2Mg6Zn3.The eutectic product enhances the mechanical properties of the studied alloy,causing strengthening and providing superior hardness values.In this alloy,cracks initiate at the intermetallic compounds and progress through the matrix because of the open network formed by the eutectics.Attending to the corrosion results,the eutectic product presents a noble potential compared to the a-Mg phase.For this reason,the corrosion progresses preferentially through the matrix,avoiding the(α-Mg+Ca2Mg6Zri3)eutectic product,when the alloy is in direct contact to Hank's solution.展开更多
The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg-Sn-Ca （TX） alloys was studied in the temperature range of 25-250 °C and correlated with the microstructure. The Sn to Ca mass ...The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg-Sn-Ca （TX） alloys was studied in the temperature range of 25-250 °C and correlated with the microstructure. The Sn to Ca mass ratio up to 2.5 contributes to the formation of Mg2Ca phase at the grain boundaries and CaMgSn in the matrix, while a ratio of 3 gives only CaMgSn phase mostly in the matrix. While the compressive strength decreases with the increase in temperature, for Sn/Ca up to 2.5, a plateau occurs in 100-175 °C, which is attributed to the strengthening by Mg2Ca. However, for ratio of 3, the strength is lower and decreases more gradually. Mg-3Sn-2Ca （TX32） has the highest strength and the addition of 0.4%Al increases its strength but simultaneous addition of Si lowers the strength. Likewise, the addition of Zn improves its strength but simultaneous addition of Al slightly decreases the strength. The results are correlated with the types of intermetallic phases that form in various alloys.展开更多
Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids(SBFs). The influence of materials,solutions and their temperature on corrosion rate w...Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids(SBFs). The influence of materials,solutions and their temperature on corrosion rate was mainly discussed. The results demonstrate that the free corrosion potential(Ecorr) of AZ31 and AZ91 alloys rises rapidly at initial stage,and then stabilizes at some value. Ecorr of WE43 alloy increases continuously. While Ecorr of AZ91 alloy with macro-arc oxidation(MAO) coating decreases drastically in 3 min,and then fluctuates between -1 607 mV and -1 503 mV. The WE43 alloy has better corrosion resistance in Hank's solution,compared with AZ31 and AZ91 alloys. Corrosion rates of the alloys are sensitive to the chemical composition and temperature of SBFs. A thin MgF2 film slightly improves corrosion resistance. An MAO coating on AZ91 alloy significantly reduces corrosion rate and enhances Ecorr. Pitting corrosion occurs on both AZ31 and WE43 alloys in Hank's solution.展开更多
Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed...Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.展开更多
A cup-shaped component of Mg-4 Al-2 Ba-2 Ca（ABa X422） alloy was forged in the temperature range of 300-500 °C and at speeds in the range of 0.01-10 mm/s with a view to validate the processing map and study the ...A cup-shaped component of Mg-4 Al-2 Ba-2 Ca（ABa X422） alloy was forged in the temperature range of 300-500 °C and at speeds in the range of 0.01-10 mm/s with a view to validate the processing map and study the microstructural development. The process was simulated through finite-element method to estimate the local and average strain rate ranges in the forging envelope. The processing map exhibited two domains in the following ranges：（1） 300-390 °C and 0.0003-0.001 s^-1, and（2） 400-500 °C and 0.0003-0.3 s^-1 and both represented dynamic recrystallization（DRX）. The map revealed a wide flow instability regime at higher strain rates and temperatures lower than 400 °C, in which flow localization occurred. Forgings produced under conditions of the above two domains were sound and symmetrical, and had finer grain sizes when being forged in the first domain. However, when being forged in the flow instability regimes, the alloy fractured before the final shape was reached. The experimental load-stroke curves for the conditions within the domains correlated well with the simulated ones, whereas the curves obtained in the instability regime were uneven.展开更多
文摘The corrosion behavior of Mg-10Gd-xZn(x=2,6 wt.%)alloys in 0.5 wt.%NaCl solution was investigated.Microstructures of both the alloys consisted of(Mg,Zn)_(3) Gd phase and lamellar long period stacking ordered(LPSO)phase.The morphology of the second phase at the grain boundary differed in both alloys:it was a continuous network structure in Mg-10Gd-6Zn,whereas it was relatively discrete in Mg-10Gd-2Zn.The dendrites were finer in size and highly branched in Mg-10Gd-6Zn.The corrosion results indicated that the increase in Zn content increased the corrosion rate in Mg-10Gd-xZn alloys.Micro-galvanic corrosion occurred near the grain boundary in both alloys initially as the grain boundary phase was stable and acted as a cathode,however,filiform corrosion dominated in the later stage,which was facilitated by the LPSO phase in the matrix.Severe micro-galvanic corrosion occurred in Mg-10Gd-6Zn due to the higher volume of second phase.The stability of the second phase at the grain boundary was altered and dissolved after the long immersion times.Probably the NaCl solution chemically reacted with the grain boundary phase and de-stabilized it during the long immersion times,and was removed by the chromic acid used for the corrosion product removal.
基金The authors would like to acknowledge the financial support from the Agencia Estatal de Investigacion(Project RTI2018-096391-B-C31)Comunidad de Madrid(Project ADITIMAT-CM S2018/NMT-4411)the FPU grant(15/03606)from the Ministerio de Educacion,Cultura y Deporte,Spain.
文摘The as-cast Mg-3Zn-0.4Ca alloy shows a great potential to be used in biomedical applications due to its composition,mechanical properties and biodegradability.Zn and Ca appear naturally in the organism accomplishing vital functions.The alloy consists of an a-Mg matrix and a eutectic composed of a-Mg4-Ca2Mg6Zn3.The eutectic product enhances the mechanical properties of the studied alloy,causing strengthening and providing superior hardness values.In this alloy,cracks initiate at the intermetallic compounds and progress through the matrix because of the open network formed by the eutectics.Attending to the corrosion results,the eutectic product presents a noble potential compared to the a-Mg phase.For this reason,the corrosion progresses preferentially through the matrix,avoiding the(α-Mg+Ca2Mg6Zri3)eutectic product,when the alloy is in direct contact to Hank's solution.
基金supported by General Research Funds (Projects#115108 and#114809) from the Research Grants Council of the Hong Kong SAR,China
文摘The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg-Sn-Ca （TX） alloys was studied in the temperature range of 25-250 °C and correlated with the microstructure. The Sn to Ca mass ratio up to 2.5 contributes to the formation of Mg2Ca phase at the grain boundaries and CaMgSn in the matrix, while a ratio of 3 gives only CaMgSn phase mostly in the matrix. While the compressive strength decreases with the increase in temperature, for Sn/Ca up to 2.5, a plateau occurs in 100-175 °C, which is attributed to the strengthening by Mg2Ca. However, for ratio of 3, the strength is lower and decreases more gradually. Mg-3Sn-2Ca （TX32） has the highest strength and the addition of 0.4%Al increases its strength but simultaneous addition of Si lowers the strength. Likewise, the addition of Zn improves its strength but simultaneous addition of Al slightly decreases the strength. The results are correlated with the types of intermetallic phases that form in various alloys.
基金Project (8655) supported by the Natural Science Foundation of Chongqing Municipal Science and Technology Commission, ChinaProject(50405005) supported by the National Science Foundation of China
文摘Potentiodynamic electrochemical technique was utilized to study the corrosion behavior of magnesium alloys in simulated body fluids(SBFs). The influence of materials,solutions and their temperature on corrosion rate was mainly discussed. The results demonstrate that the free corrosion potential(Ecorr) of AZ31 and AZ91 alloys rises rapidly at initial stage,and then stabilizes at some value. Ecorr of WE43 alloy increases continuously. While Ecorr of AZ91 alloy with macro-arc oxidation(MAO) coating decreases drastically in 3 min,and then fluctuates between -1 607 mV and -1 503 mV. The WE43 alloy has better corrosion resistance in Hank's solution,compared with AZ31 and AZ91 alloys. Corrosion rates of the alloys are sensitive to the chemical composition and temperature of SBFs. A thin MgF2 film slightly improves corrosion resistance. An MAO coating on AZ91 alloy significantly reduces corrosion rate and enhances Ecorr. Pitting corrosion occurs on both AZ31 and WE43 alloys in Hank's solution.
文摘Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.
基金fully supported by Strategic Research Grant (Project #7002744) from the City University of Hong Kong, China
文摘A cup-shaped component of Mg-4 Al-2 Ba-2 Ca（ABa X422） alloy was forged in the temperature range of 300-500 °C and at speeds in the range of 0.01-10 mm/s with a view to validate the processing map and study the microstructural development. The process was simulated through finite-element method to estimate the local and average strain rate ranges in the forging envelope. The processing map exhibited two domains in the following ranges：（1） 300-390 °C and 0.0003-0.001 s^-1, and（2） 400-500 °C and 0.0003-0.3 s^-1 and both represented dynamic recrystallization（DRX）. The map revealed a wide flow instability regime at higher strain rates and temperatures lower than 400 °C, in which flow localization occurred. Forgings produced under conditions of the above two domains were sound and symmetrical, and had finer grain sizes when being forged in the first domain. However, when being forged in the flow instability regimes, the alloy fractured before the final shape was reached. The experimental load-stroke curves for the conditions within the domains correlated well with the simulated ones, whereas the curves obtained in the instability regime were uneven.
