清華材料科學(xué)基礎(chǔ)課件(英文)skja_25.ppt

1、2020/7/23,材料科學(xué)基礎(chǔ),材料科學(xué)基礎(chǔ)Fundamental of Materials,Prof: Tian Min Bo Tel: 62795426 ，62772851 E-mail: Department of Material Science and Engineering Tsinghua University. Beijing 100084,Lesson twenty-five,2020/7/23,材料科學(xué)基礎(chǔ),5.18 Thompsons tetrahedron,2020/7/23,材料科學(xué)基礎(chǔ),5.19 Reaction between Dislocation,.Cond

2、ition Geometrical condition Energy condition,2020/7/23,材料科學(xué)基礎(chǔ),.Example (FCC),2020/7/23,材料科學(xué)基礎(chǔ),2020/7/23,材料科學(xué)基礎(chǔ),Lomer-Cottrell sessile dislocation,2020/7/23,材料科學(xué)基礎(chǔ),Dislocation network,2020/7/23,材料科學(xué)基礎(chǔ),2020/7/23,材料科學(xué)基礎(chǔ),2020/7/23,材料科學(xué)基礎(chǔ),2020/7/23,材料科學(xué)基礎(chǔ),5.20 Simple Applications of Dislocation Theory,.C

3、rystal Growth and Interfacial Structure Crystal Growth,Vapor Solid ; Liquid Solid,2020/7/23,材料科學(xué)基礎(chǔ),TLK Model The necessary supersaturation for crystal growth will be smaller if the steps are available on the solid surface Screw dislocation can provide such steps which will never disappear in the cou

4、rse of growth.,Interfacial Structure,2020/7/23,材料科學(xué)基礎(chǔ),.Small angle grain boundary (or G.B. with small misorientation) and grain boundary strengthen. Model for grain boundary Tilt g.b. Twist g.b. General small angle boundary Grain boundary strengthen and Hall-Petch,2020/7/23,材料科學(xué)基礎(chǔ),.Strain hardening

5、(work hardening) .Annealing (softening) decreases due to the annihilation of the dislocations of opposite sign which can either slip or climb in annealing.,2020/7/23,材料科學(xué)基礎(chǔ),.Alloy hardening Solid Solution hardening (disorder) homogeneous distribution preferential distribution Homogeneous distribution: Preferential distribution,Resist to dislocation movement by the long-range stress field induced by the solute atoms.,2020/7/23,材料科學(xué)