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1、Fundamentals of Material Science and Engineering材料科学与工程基础材料科学与工程基础Chapter 88.Deformation and Strengthening MechanismRecovery,Recrystallization,and Grain Growth8.12 Recovery8.13 Recrystallization8.14 Grain GrowthDeformation and Strengthening Mechanisms Recovery 回复回复 Recrystallization 再结晶再结晶Chapter 8D
2、eformation and Strengthening MechanismsRecovery,Recrystallization,and Grain GrowthPlastically deformed at low temperaturechange in grain shapestrain hardeningdislocation density increasingStrain energyOther propertiesthe precold-work statesRecoveryRecrystallizationChapter 8Deformation and Strengthen
3、ing Mechanisms8.12 RecoverynDuring Recovery:Boundary 边界边界 Barrier 障碍物障碍物 Discontinuity 不连续性不连续性Elevated temperatureEnhanced atomic diffusionDislocation reductionStrain energy relievingMechanical properties recovered at certain degree.Physical properties recovered totally.见补充材料（见补充材料（P213）Chapter 8De
4、formation and Strengthening Mechanisms8.12 Recrystallizationn RecrystallizationnDriving force of Recrystallization:the difference in internal energy between the strained and unstrained material.New strain-free and equiaxed grains appear.Mechanical properties restore to their precold-working values.T
5、he stages refer to Fig.8.21Chapter 8Deformation and Strengthening MechanismsChapter 8Deformation and Strengthening MechanismsnDependence of recrystallization on both time and temperature(Fig.8.22)Recrystallization temperatureTypically between 1/3 1/2 of Tm.Increasing the percentage of cold work,lowe
6、r the recrystallization temperature.Limit value in the literature.Exist critical degree of cold workChapter 8Deformation and Strengthening MechanismsChapter 8Deformation and Strengthening Mechanisms8.14 Grain Growthn Grain Growth:the Strain-free grains continue to grow if the specimen still be left at elevated temperature.Chapter 8Deformation and Strengthening MechanismsDriving force:grains increase in size,grain boundary area decreases,and result in total energy reduction.Large ones grow,small ones shrink.Directions of atomic motion and the boundary are opposite.