N.C.Si and S.C.Sun Departmentof Materials Engineering
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Jiangsu University of Science and Technology
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Zhenjiang 212013
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China
金属学报(英文版)
With thehelpofquantitative metallograph ,tensiletest,electron probeandscan electron mi croscope,theinfluencesof mixture rareearth ( RE) on the grain size, dynamics of grain growth and mechanicalpropertiesof CuZnAlshape memoryalloys wereinvestigated . Theex perimentalresultsshowsthat REcanrefinegrainsgreatly,improvethe mechanicalpropertiesremarkably andchangethetensilefracturefrom brittletypebordered grainstoplastictypeinthecondition of maintainingshape memory properties. Moreover microstructuresrevealthatREwhich accumulates on the grain boundariescan restrain grains’growing. In addition, the mechanismsofrefininggrainsizeandimproving mechanicalpropertiesarealsodiscussed.
关键词:
rareearth
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N.C.Si and S.C.Sun Departmentof Materials Engineering
,
Jiangsu University of Science and Technology
,
Zhenjiang 212013
,
China
金属学报(英文版)
Theinfluencesofthermalcycleson propertiesof CuZnAlshape memory alloysunder differentheatingtemperatures, pre deformation amountεand addition amountofcomplex rareearthmixture wereresearched with X ray diffraction and electron microscope. Theresultsindicate thatthermalcyclescanincreasethetransformationtemperatureofthealloysby 5～6℃.In creasingthe pre deformation amount will decrease the necessary cycle times for stabletwo -wayshape memory property. Howevertheshaperecovery rateofthealloy willdecreaseasthepre deformation amountexceeds3 6 % . Theshape memory propertyofthealloy willchangeinsignificantlyiftheaddition amountofrareearthislessthan 0 10 % . Butthealloys with outrareearth willhave worseshape memory property afterthermalcyclesreach 1800 times.
关键词:
thermalcycle
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QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
,
Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
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