北航考研復(fù)試15專業(yè)英語(yǔ)msei-06a

1、Dislocation and Strength Mechanisms第六講Important terms and conceptsSlipResolved shear stressCold workingHot workingRecovery and RecrystallizationSolid-solution strengtheningStrain hardeningThe motion of a screw dislocation in response to the applied shear stress, the direction of movement is perpendi

2、cular to the stress direction.The motion of an edge dislocation is parallel to the shear stress.Characteristics of dislocationSlipThe process by which plastic deformation is produced by dislocation motion is termed as slip.Slip planeThe crystallographic plane along which the dislocation line travers

3、es is the slip plane.Slip systemThe combination of the slip plane and slip direction is termed as slip systemMechanisms of strengtheningAll strengthening techniques rely on this simple principle: restricting or hindering dislocation motion renders a material harder and stronger.Mechanisms of strengt

4、hening (I)Strengthening by grain size reductionHall-Petch equationMechanisms of strengthening (II)Solid-solution strengtheningLattice strain(size, electron, chemical)Mechanisms of strengthening (III)Strain hardeningWorking hardeningDislocation densityStrain-hardening exponentDevelopment of Strain Ha

5、rdeningRecrystallizationRecoveryGrain GrowthAnnealing ProcessRecoverStored internal strain energyDislocation configurationRecrystallizationStrain-free grainsEquiaxed grainsRecrystallization temperatureAt higher temperatures, both recovery and recrystallization rapidly occur, producing the fine recrystallized grain structure.Energy associated with the large amount of grain boundary area makes the fine structure unstable at higher temperaturesGrain growth is almost always undesirableGrain growthDefined as plastically deforming the metal at a