1.(a)Draw a typical stress strain curve for a precipitation-hardening system containing small,coherent,G-P zone.What is the model of dislocation motion in such a crystal and what is the rate controlling mechanism in the model? (b)What is the Orowan Friedel relation for flow stress in a dispersion-hardening system and how does it relate to microstructural parameters?Assume intermediate strength obstacles. 2.a)Discuss the complications in determining the true stress-true strain diagram in tension. b)Give a basic definition of toughness.What is involved in the engineering concept of toughness? c)Using the von Mises yielding condition,at what value of o will you expect yielding for the state of stresso2=20.(o =0)? d)In an elastic triaxial stress state (o1,02,03)give the expression for o2 in plane strain(δ，=O) 3.a)Discuss the implications of macroscopic compatibility constraints on the deformation of a grain in a poly-crystal.Discuss both elastic and plastic effects. b)What is the Friedel-Orowan equation To what classes of engineering alloys or microstructures is it applicable? 4.Explain how high-temperature creep is controlled by self diffusion, i)in the Nabarro-Herring Creep region ii)in the Andrade"power"creep region where ko4s, iii)how do the following factors affect Andrade "power"creep? iv)grain size v)stacking fault energy vi)temperature 5.(a)Explain how recrystallization textures can be formed in a severely cold worked alloy. (b)Explain how each of the following can influence the development of a crystallization texture. (i)A fine ppt.(e.g.,AIN in steel)which goes into solution slowly on heating. (ii)The inadvertent formation of y grains in a Fe-3Si which has been annealed at 1150 C.(It is inadvertent because the steel would have remained all a if it had been adequately decarburied before1. (a) Draw a typical stress strain curve for a precipitation-hardening system containing small, coherent, G-P zone. What is the model of dislocation motion in such a crystal and what is the rate controlling mechanism in the model? (b) What is the Orowan Friedel relation for flow stress in a dispersion-hardening system and how does it relate to microstructural parameters? Assume intermediate strength obstacles. 2. a) Discuss the complications in determining the true stress-true strain diagram in tension. b) Give a basic definition of toughness. What is involved in the engineering concept of toughness? c) Using the von Mises yielding condition, at what value of σ 1 will you expect yielding for the state of stress 2 2 .( 0) σ = σ σ y = ? d) In an elastic triaxial stress state 123 (, , ) σ σ σ give the expression for σ 2 in plane strain ( 2 δ = 0 ) 3. a) Discuss the implications of macroscopic compatibility constraints on the deformation of a grain in a poly-crystal. Discuss both elastic and plastic effects. b) What is the Friedel-Orowan equation ? To what classes of engineering alloys or microstructures is it applicable? 4. Explain how high-temperature creep is controlled by self diffusion, ⅰ) in the Nabarro-Herring Creep region ⅱ) in the Andrade “power” creep region where , 4.5 kσ ⅲ) how do the following factors affect Andrade “power” creep? ⅳ） grain size ⅴ) stacking fault energy ⅵ) temperature 5. (a) Explain how recrystallization textures can be formed in a severely cold worked alloy. (b) Explain how each of the following can influence the development of a crystallization texture. (ⅰ) A fine ppt.(e.g., AlN in steel) which goes into solution slowly on heating. ( ) The inadvertent formation of ⅱ γ grains in α Fe-3Si which has been annealed at 1150 C. (It is inadvertent because the steel would have remained all α if it had been adequately decarburied before