skja_14 Rotation of Crystal during Slip 材料科学基础（英文课件）.pptVIP

材料科学基础Fundamental of Materials §4.4 Rotation of Crystal during Slip Ⅰ.The cause of rotation: Due to constraints, or boundary conditions, imposed on the crystal. Ⅱ.The rule of rotation : 1) axis of rotation ∥ ∥ 2) During slip, the S.D. tends to approach to loading direction in tension. During slip, the S.P. tends to approach to compression plane in compression. Ⅲ.The consequence of rotation : 1. Change in length of the specimen ② Geometrical softening in tension Schmid’s law at the onset of slip: slip system: locus: F tend to , ∥ ∥ stable: §4.5 Surface Morphology of Crystal After Slip The following deformation marks can be seen on the surface of the crystal after slip. Slip lines: the steps formed on surface due to slip. Slip bands. Deformation band formed due to inhomogeneous rotation. Kink bands §4.6 Strain Hardening (Work-hardening) Strain Hardening curve of single crystal —— curve. It can be divided in to three stages: for Ⅰ: Easy-glide for Ⅱ: Linear hardening is very great for Ⅲ: Parabolic hardening ↓ flow stress How to obtain curve §4.7 Twinning(Ⅰ)  ——Microscopic Aspect Ⅰ. Basic feature of twinnings. Twinning is a translational movements of one portion of the crystal with respect to the other on a specific plane called twinning plane and along a specific orientation relationship between the two portion of crystals. Ⅱ.Twinning system. A Twinning plane plus a twinning direction lying on it is called a twinning system. Twinning systems for FCC, BCC and HCP. It is more difficult for twinning systems to occur than slip systems, because (twinning). Ⅲ.Atom movements in twinning of FCC To show movements, all atoms should be projected onto shear plane and contains twinning direction. Discussion Examples and Discussions Exer