材料科学与工程基础经典课件Fundamentals11.pptVIP

Fundamentals of Material Science and Engineering 材料科学与工程基础 * * Chapter 8 8. Deformation and Strengthening Mechanism Mechanisms of Strengthening in Metals 8.9 Strengthening by Grain Size Reduction 8.10 Solid-Solution Strengthening 8.11 Strain Hardening Deformation and Strengthening Mechanisms Deformation 形变 Strengthen 强化 Mechanism 机制 Reduction 减小 Dislocation motion ?? mechanical behavior: the ability of a metal to plastically deform depends on the ability of dislocations to move; Strengthening mechanicals: grain size reduction, solid-solution alloying and strain hardening. All strengthening techniques rely on this simple principle: restricting or hindering dislocation motion renders a material harder and stronger. Chapter 8 Deformation and Strengthening Mechanisms Mechanisms of Strengthening in Metals Restrict 限制，约束 Hinder 阻碍 Render 使得 Principle 原理 Chapter 8 Deformation and Strengthening Mechanisms 8.9 Strengthening by Grain Size Reduction The grain boundary acts as a barrier to dislocation motion for two reasons: Change its direction of motion; Discontinuity of slip planes. For the high-angle grain boundaries, not traverse, but reproduce a new dislocation. Boundary 边界 Barrier 障碍物 Discontinuity 不连续性 Chapter 8 Deformation and Strengthening Mechanisms Chapter 8 Deformation and Strengthening Mechanisms Hall Petch equation （霍尔佩奇公式） Not valid for both very large grain and extremely fine grain polycrystalline materials. Improve not only strength, but also ductility. Small angle boundary, twin boundary and phase boundary… Chapter 8 Deformation and Strengthening Mechanisms 8.10 Solid-solution Strengthening Solid-solution strengthening: strengthening techniques by alloying with impurity atoms that go into either substitutional or interstitial solid solution *