材料科學(xué)基礎(chǔ)第05章9

1、材料科學(xué)基礎(chǔ)Fundamental of MaterialsProf: Tian Min Bo Tel: 62795426 ，62772851 E-mail: Department of Material Science and EngineeringTsinghua University. Beijing 100084Lesson twenty-five5.18 Thompsons tetrahedron5.19 Reaction between Dislocation.ConditionGeometrical conditionEnergy condition.Example (FCC)B

2、BCLomer-Cottrell sessile dislocation Dislocation network 5.20 Simple Applications of Dislocation Theory.Crystal Growth and Interfacial StructureCrystal GrowthVapor Solid ; Liquid SolidGTToGvapGsolTLK ModelThe necessary supersaturation for crystal growth will be smaller if the steps are available on

3、the solid surfaceScrew dislocation can provide such steps which will never disappear in the course of growth.Interfacial Structure.Small angle grain boundary (or G.B. with small misorientation) and grain boundary strengthen.Model for grain boundaryTilt g.b.Twist g.b.General small angle boundaryGrain

4、 boundary strengthen and Hall-Petch.Strain hardening (work hardening).Annealing (softening) decreases due to the annihilation of the dislocations of opposite sign which can either slip or climb in annealing.Alloy hardening Solid Solution hardening (disorder) homogeneous distribution preferential distributionHomogeneous distribution: Preferential distributionResist to dislocation movement by the long-range stress field indu