The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solut...The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.展开更多
The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening pr...The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.展开更多
Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 allo...Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.展开更多
Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was...Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was investigated.Steel samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,respectively.Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated sample.Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample.The electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance spectroscopy.As a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated sample.The impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.展开更多
A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior...A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.展开更多
The microstructures and properties of Cu-8.0Ni-1.8Si alloy subjected to different heat treatments were examined by mechanical and electrical properties measurements,optical and transmission electron microscopes observ...The microstructures and properties of Cu-8.0Ni-1.8Si alloy subjected to different heat treatments were examined by mechanical and electrical properties measurements,optical and transmission electron microscopes observation. The results show that the precipitation process during aging can be accelerated by the cold deforming before aging. As the Cu-8.0Ni-1.8Si alloy is subjected to solution treatment at 970 ℃ for 4 h,cold rolling to 60% reduction,and then aging at 450 ℃ for 60 min,its properties are σb=1 050 MPa,σ0.2=786 MPa,δ=3.2% and conductivity 27.9%(IACS). The strengthening mechanisms of the alloy include spinodal decomposition strengthening,ordering strengthening and precipitation strengthening. The precipitation of the alloy is nano-scale Ni2Si phase.展开更多
The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings.The relatively new ferrous casting alloy ADI...The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings.The relatively new ferrous casting alloy ADI offers promising strength prospects,and the thermo-mechanical treatment of ductile iron may suggest a new route for production of thin-wall products.This work aims at studying the influence of thermomechanical treatment,either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after austempering.In the first part of this work,ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment,thus increasing the rate of ausferrite formation and leading to a much finer and more homogeneous ausferrite product.The kinetics of ausferrite formation was studied using both metallographic as well as XRD-techniques.The effect of ausforming on the strength was quite dramatic(up to 70% and 50% increase in the yield and ultimate strength respectively).A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested.Nickel is added to ADI to increase hardenability of thick section castings,while ausforming to higher degrees of deformation is necessary to alleviate the deleterious effect of alloy segregation on ductility.In the second part of this work,the influence of cold rolling(CR)on the mechanical properties and structural characteristics of ADI was investigated.The variation in properties was related to the amount of retained austenite(γr)and its mechanically induced transformation.In the course of tensile deformation of ADI,transformation induced plasticity(TRIP)takes place,indicated by the increase of the instantaneous value of strain-hardening exponent with tensile strain.The amount of retained austenite was found to decrease due to partial transformation of γr to martensite under the CR strain.Such strain-induced transformation resulted in higher amounts of mechanically generated martensite.The strength and hardness properties were therefore increased,while ductility and impact toughness decreased with increasing CR reduction.展开更多
The effect of thermomechanical treatment on the magnetic properties of Mn85.5Fe9.0Cu0.5 alloy was studied by use of a materials testing machine, a vibrating sample magnetometer, an X-ray diffractometer, a homogeneousl...The effect of thermomechanical treatment on the magnetic properties of Mn85.5Fe9.0Cu0.5 alloy was studied by use of a materials testing machine, a vibrating sample magnetometer, an X-ray diffractometer, a homogeneously and adjustably magnetic field and strain gauges. The results show that the orientation of fct phase and magnetic domains is affected by the thermomechanical treatment. When the compressive strain of thermomechanical treatment is -1.2%, the magnetic-field-induced strain reaches the highest value in the adapted situation.展开更多
The aim of this work is the demonstration of the effect of thermomechanical treatments on the properties of the alloy Al-5.8%Zn-2.7%Mg by thermal analysis techniques and calorimetry, which are methods of test widely u...The aim of this work is the demonstration of the effect of thermomechanical treatments on the properties of the alloy Al-5.8%Zn-2.7%Mg by thermal analysis techniques and calorimetry, which are methods of test widely used for research purposes and quality control. The effects of thermomechanical treatments on the two variables namely the coefficient of thermal expansion and heat capacity, we can provide further information for better understanding of the phenomena responsible for the thermodynamic behavior of the alloy. The results showed the one hand, there is great similarity between the linear coefficient of thermal expansion and heat capacity, and secondly the effect of plastic deformation is evidenced by changes in the shape of the curves from the rough. Similarly the kinetics of precipitation of η phase is accelerated in the case of samples homogenized and homogenized + distorted and accompanied by a shift in the temperature range to lower temperatures than those recorded in the case of the material state Gross.展开更多
基金financially supported by the National High-Tech Research and Development Program of China (No.2006AA03Z522)the National Natural Science Foundation of China (No.50704006)the Technology De-velopment Fund of CHALCO (No.CHINACO-2009-KJ-02)
文摘The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.
基金Funded by the National Key Technology R&D Program of China(No.2007BAE38B01)
文摘The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.
文摘Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.
文摘Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was investigated.Steel samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,respectively.Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated sample.Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample.The electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance spectroscopy.As a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated sample.The impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.
基金Project(2001AA332010) supported by the National Advanced Materials Committee of China
文摘A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.
基金Project(20040533069) supported by Doctoral Fund of the Ministry of Education, China
文摘The microstructures and properties of Cu-8.0Ni-1.8Si alloy subjected to different heat treatments were examined by mechanical and electrical properties measurements,optical and transmission electron microscopes observation. The results show that the precipitation process during aging can be accelerated by the cold deforming before aging. As the Cu-8.0Ni-1.8Si alloy is subjected to solution treatment at 970 ℃ for 4 h,cold rolling to 60% reduction,and then aging at 450 ℃ for 60 min,its properties are σb=1 050 MPa,σ0.2=786 MPa,δ=3.2% and conductivity 27.9%(IACS). The strengthening mechanisms of the alloy include spinodal decomposition strengthening,ordering strengthening and precipitation strengthening. The precipitation of the alloy is nano-scale Ni2Si phase.
文摘The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings.The relatively new ferrous casting alloy ADI offers promising strength prospects,and the thermo-mechanical treatment of ductile iron may suggest a new route for production of thin-wall products.This work aims at studying the influence of thermomechanical treatment,either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after austempering.In the first part of this work,ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment,thus increasing the rate of ausferrite formation and leading to a much finer and more homogeneous ausferrite product.The kinetics of ausferrite formation was studied using both metallographic as well as XRD-techniques.The effect of ausforming on the strength was quite dramatic(up to 70% and 50% increase in the yield and ultimate strength respectively).A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested.Nickel is added to ADI to increase hardenability of thick section castings,while ausforming to higher degrees of deformation is necessary to alleviate the deleterious effect of alloy segregation on ductility.In the second part of this work,the influence of cold rolling(CR)on the mechanical properties and structural characteristics of ADI was investigated.The variation in properties was related to the amount of retained austenite(γr)and its mechanically induced transformation.In the course of tensile deformation of ADI,transformation induced plasticity(TRIP)takes place,indicated by the increase of the instantaneous value of strain-hardening exponent with tensile strain.The amount of retained austenite was found to decrease due to partial transformation of γr to martensite under the CR strain.Such strain-induced transformation resulted in higher amounts of mechanically generated martensite.The strength and hardness properties were therefore increased,while ductility and impact toughness decreased with increasing CR reduction.
基金This work was supported by the stae“863 plan”,under Grant No.2002AA331112by the Major Science and Technology Project of Henan Province,China,under Grant No.0122021300.
基金Project(20080441084) supported by China Postdoctoral Science FoundationProject(2007GCZ1714) supported by the Natural Science Foundation of Jiangxi Province, ChinaProject (GJJ08004) supported by Education Bureau of Jiangxi Province, China
文摘The effect of thermomechanical treatment on the magnetic properties of Mn85.5Fe9.0Cu0.5 alloy was studied by use of a materials testing machine, a vibrating sample magnetometer, an X-ray diffractometer, a homogeneously and adjustably magnetic field and strain gauges. The results show that the orientation of fct phase and magnetic domains is affected by the thermomechanical treatment. When the compressive strain of thermomechanical treatment is -1.2%, the magnetic-field-induced strain reaches the highest value in the adapted situation.
文摘The aim of this work is the demonstration of the effect of thermomechanical treatments on the properties of the alloy Al-5.8%Zn-2.7%Mg by thermal analysis techniques and calorimetry, which are methods of test widely used for research purposes and quality control. The effects of thermomechanical treatments on the two variables namely the coefficient of thermal expansion and heat capacity, we can provide further information for better understanding of the phenomena responsible for the thermodynamic behavior of the alloy. The results showed the one hand, there is great similarity between the linear coefficient of thermal expansion and heat capacity, and secondly the effect of plastic deformation is evidenced by changes in the shape of the curves from the rough. Similarly the kinetics of precipitation of η phase is accelerated in the case of samples homogenized and homogenized + distorted and accompanied by a shift in the temperature range to lower temperatures than those recorded in the case of the material state Gross.
