A reversible martensitic transformation (MT) takes place during cooling and heating in the solution quenched and the solution quenched plus aged Ni59AlHMn30 alloy The MT temperature increases with increasing solution ...A reversible martensitic transformation (MT) takes place during cooling and heating in the solution quenched and the solution quenched plus aged Ni59AlHMn30 alloy The MT temperature increases with increasing solution temperature. The excellent MT characteristics can be obtained from a process of lOOCTC solution quenched plus 400 °C aged. Follow this process, the MT start temperature (Ms) and the reverse MT finish temperature (Af) are 469*C and 548"C, respectively. The martensitic stabilization effect in the solution quenched and aged Ni59AlnMn3o alloy is observed as an increase in the Af temperature of the first reverse MT during thermal cycles. This stabilization effect vanishes from the second thermal cycle. Thermal cycling can enhance the stability of the reversible MT. The microstructure of the quenched NisgAlnMnjo alloy consists of martensite (M) and gamma phase. The volume fraction of gamma phase is about 40%. The substructure of M and gamma phase is twins and dislocations, respectively. The hardness of M is higher than that of gamma phase. After aging treatment the basic phases of alloy do not change, but the hardness of the phases increases.展开更多
The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at. pci Ni alloy. It is shown that Ms and Mf temperature increase with increasing ...The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at. pci Ni alloy. It is shown that Ms and Mf temperature increase with increasing the number of cycles, while As and Af temperature decrease during thermal cycling. The total strain et and permanent strain ep increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.展开更多
The thermal-mechanical (T-M) cycles at constant strain of a polycrystalline CuZnAl alloy have been studied in the. present work. In-situ optical microscopic observations have been made to reveal the features of the ph...The thermal-mechanical (T-M) cycles at constant strain of a polycrystalline CuZnAl alloy have been studied in the. present work. In-situ optical microscopic observations have been made to reveal the features of the phase transitions during T-M cycling. The variation of stress-temperature (S-T) curves and electrical resistance-temperature (R-T) curves accompanying with T-M cycling have been measured by tensile test and electrical resistance measurements. It has been found that the polycrystalline CuZnAl alloy shows apparent morphology changes and properties variations in the first cycle during T-M cycling which is called the first cycle effect in the present work. The stable transformation procedure in the T-M cycle is: martensiteparent phase +residual acicular martensite. This residual martensite possesses the character of stress-induced martensite.展开更多
The effects of thermal cycling on martensite transformation in Cu 11.9Al 2.5Mn(mass fraction, %) shape memory alloy(SMA) with high M s temperature were studied by means of electrical tension vs temperature ( U-T ) mea...The effects of thermal cycling on martensite transformation in Cu 11.9Al 2.5Mn(mass fraction, %) shape memory alloy(SMA) with high M s temperature were studied by means of electrical tension vs temperature ( U-T ) measurement, optical microscopy observation and X ray diffractometry. It shows that with increasing thermal cycles, the transformation temperatures decreased, which are accompanied by changes of martensite structure such as the decline of NNN ordering degree and monoclinic angle β →90°. Compared with traditional Cu base SMA, the alloy has rather high thermostability and can work at 200～300?℃. Its excellent thermostability comes from two factors: 1) its β 1 parent structure is stable and difficult to decompose at work temperature; 2) its martensite structure is close to N18R( β =89.6°), which restrains the process of M18R→N18R and the tendency of martensite stabilization and decomposition.展开更多
The basic martensitic transformation （MT） properties of Ru50Ta50 alloy, i.e. MT temperature （MTT）, temperature hysteresis （△T）, and MT heat （△H） were investigated in this paper. The effects of heat treatment...The basic martensitic transformation （MT） properties of Ru50Ta50 alloy, i.e. MT temperature （MTT）, temperature hysteresis （△T）, and MT heat （△H） were investigated in this paper. The effects of heat treatment and thermal cycling on MT behavior of Ru50Ta50 alloy, the deformation and microstructure characteristics of Ru50Ta50 alloy were also studied for its engineering application as high temperature actuator/sensor materials by means of differential scanning calorimetry, X-ray diffraction, transmission electron microscope, optical microscope, and hardness test. The results showed that a two-stage reversible MT takes place in Ru50Ta50 alloy. The two-stage MT starting temperatures （Ms^1, Ms^2） and the temperature hysteresis （△T1, △T2） are 1047, 784 and 11, 14℃, respectively. No significant effect of aging treatment and thermal cycling on MTT and AT of Ru50Ta50 alloy were observed, but △H decreases slowly with increasing thermal cycles. The hardness and brittleness of Ru50Ta50 alloy are high. The deformation mode of RuTa alloys is twinning.展开更多
基金supported by the Science Foundation of Shaanxi University of Technology(No.SLG0332).
文摘A reversible martensitic transformation (MT) takes place during cooling and heating in the solution quenched and the solution quenched plus aged Ni59AlHMn30 alloy The MT temperature increases with increasing solution temperature. The excellent MT characteristics can be obtained from a process of lOOCTC solution quenched plus 400 °C aged. Follow this process, the MT start temperature (Ms) and the reverse MT finish temperature (Af) are 469*C and 548"C, respectively. The martensitic stabilization effect in the solution quenched and aged Ni59AlnMn3o alloy is observed as an increase in the Af temperature of the first reverse MT during thermal cycles. This stabilization effect vanishes from the second thermal cycle. Thermal cycling can enhance the stability of the reversible MT. The microstructure of the quenched NisgAlnMnjo alloy consists of martensite (M) and gamma phase. The volume fraction of gamma phase is about 40%. The substructure of M and gamma phase is twins and dislocations, respectively. The hardness of M is higher than that of gamma phase. After aging treatment the basic phases of alloy do not change, but the hardness of the phases increases.
文摘The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at. pci Ni alloy. It is shown that Ms and Mf temperature increase with increasing the number of cycles, while As and Af temperature decrease during thermal cycling. The total strain et and permanent strain ep increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.
文摘The thermal-mechanical (T-M) cycles at constant strain of a polycrystalline CuZnAl alloy have been studied in the. present work. In-situ optical microscopic observations have been made to reveal the features of the phase transitions during T-M cycling. The variation of stress-temperature (S-T) curves and electrical resistance-temperature (R-T) curves accompanying with T-M cycling have been measured by tensile test and electrical resistance measurements. It has been found that the polycrystalline CuZnAl alloy shows apparent morphology changes and properties variations in the first cycle during T-M cycling which is called the first cycle effect in the present work. The stable transformation procedure in the T-M cycle is: martensiteparent phase +residual acicular martensite. This residual martensite possesses the character of stress-induced martensite.
文摘The effects of thermal cycling on martensite transformation in Cu 11.9Al 2.5Mn(mass fraction, %) shape memory alloy(SMA) with high M s temperature were studied by means of electrical tension vs temperature ( U-T ) measurement, optical microscopy observation and X ray diffractometry. It shows that with increasing thermal cycles, the transformation temperatures decreased, which are accompanied by changes of martensite structure such as the decline of NNN ordering degree and monoclinic angle β →90°. Compared with traditional Cu base SMA, the alloy has rather high thermostability and can work at 200～300?℃. Its excellent thermostability comes from two factors: 1) its β 1 parent structure is stable and difficult to decompose at work temperature; 2) its martensite structure is close to N18R( β =89.6°), which restrains the process of M18R→N18R and the tendency of martensite stabilization and decomposition.
基金This work was supported by the Natural Science Foundation of Shaanxi Province （No.2005E121）the Natural Science Foundation of Shaanxi University of Technology（Nos.SLG0332,SLGQD0403）.
文摘The basic martensitic transformation （MT） properties of Ru50Ta50 alloy, i.e. MT temperature （MTT）, temperature hysteresis （△T）, and MT heat （△H） were investigated in this paper. The effects of heat treatment and thermal cycling on MT behavior of Ru50Ta50 alloy, the deformation and microstructure characteristics of Ru50Ta50 alloy were also studied for its engineering application as high temperature actuator/sensor materials by means of differential scanning calorimetry, X-ray diffraction, transmission electron microscope, optical microscope, and hardness test. The results showed that a two-stage reversible MT takes place in Ru50Ta50 alloy. The two-stage MT starting temperatures （Ms^1, Ms^2） and the temperature hysteresis （△T1, △T2） are 1047, 784 and 11, 14℃, respectively. No significant effect of aging treatment and thermal cycling on MTT and AT of Ru50Ta50 alloy were observed, but △H decreases slowly with increasing thermal cycles. The hardness and brittleness of Ru50Ta50 alloy are high. The deformation mode of RuTa alloys is twinning.
