Surface Effects in Crystal Plasticity

John Keats, writing to Fanny Brawne [1], said "I long to believe in immortality ••••• I wish to believe in immortality - I wish to live with you forever". So much of this talk will be concerned with the ductile behaviour of crystals, plasticity in its narrower sense. We shall consider a crystal which is deforming by slip, and shall expose a surface in this crystal. We first think of the sur­ face as a simple mathematical cut along a low-index plane. Then we allow for the relaxation of the newly-exposed atoms, and for surface irregularities, and we consider the effect of lattice va­ cancies which can enter at the surface. We consider the effect of dissolving off the surface layers, either intermittently or contin­ uously. Then the effects of adsorption or oxidation by normal con­ stituents of the atmosphere must be considered, the effects of sur­ face alloying, and finally those of special surface-active agents. But "All/Life death does end and each day dies with sleep" [2], and plasticity in its broader sense includes the fracture ~'1hich term­ inates flow. Here there is a bewildering array of effects. The medium in which the crystal flows may enhance its ductility enor­ mously, or it may cause it to break almost without plastic deform­ ation, or under a load which it has already supported.

Surface Effects in Crystal Plasticity: General Overview.- Surface Effects in Crystal Plasticity: Overview from the Crystal Plasticity Standpoint.- Surface Effects in Crystal Plasticity: Overview from a Surface Science Point of View.- Atomic Geometry and Electronic Structure of Solid Surfaces.- Space Charge Layers.- Surface Chemistry I: Multi-Component Systems.- Surface Chemistry II: Overlayers (New Phases).- Micropiasticity.- Inelastic Deformation and Fracture of Crystalline Solids.- Survey Lecture.- The Role of Surface-Environment Interactions on Cyclic Deformation.- A Surface Effect Specific to Cyclically Deformed BCC Metals — The Surface Roughening of Polycrystalline ?-Iron During Cyclic Deformation.- Dislocation Mobility in the Surface Layer.- Role of Free Surface in Yielding and Easy Glide Deformations of Highly Perfect Copper Crystals.- Microcinematographic Studies of the Development of Slip Bands.- The Plastic Flow Stress in the Core and Surface Regions of Deformed Crystals.- An Analysis of the Unloading Yield Point With Reference to the Pre-Macro-Yield Region.- New Studies of Surface Effects in Deformed Copper Single Crystals.- Influence of Surface Plasticity on the Deformation Behavior and Fracture Mode of Silicon.- On the Residual Stresses in Plastically Deformed Polycrystals and Composites.- Survey Lecture.- Surface Damage Resulting from Film Cracking.- Effect of Anodic Oxide Films on Low Temperature Mechanical Behavior of Niobium Single Crystals.- The Effect of Near-Surface Diffusion Layers on Fatigue of Copper.- Survey Lecture.- Surface Effects on the Yield Point of Sapphire.- Microdeformation of Hard Non-Metallic Crystals by Softer Indenters and Sliders.- The Chemomechanical Effect in Semiconductors.- Survey Lecture.- Chemical-Induced Variations in thePlasticity and Fracture of Metals and Minerals — Chemomechanical Effect.- Survey Lecture.- Mechanical Behavior of Oxide Free Stainless Steel Surfaces in A Low Pressure Hydrogen Environment.- A Unifying Model of Intergranular Corrosion, Intergranular Penetration of Liquid Metals, Stress Corrosion Cracking and Liquid Metal Embrlttlement of Substitutional Solid Solutions.- Cleavage vs. Shear At Crack Tips in Metal Crystals.- Nondestructive, Near-Surface Plasticity Determination by Electron Channeling.- Correlation Between Pitting and Stress Corrosion Cracking of Stainless Steels in Chloride Solutions.- What I Know and Would Like to Know Concerning Environmental Effects on the Mechanical Properties of Metals.- Survey Lecture: Applications of Chemomechanical Effects to Fracture-Dependent Industrial Processes.- Environmentally-Assisted Hard Materials Machining.- Erosion of Metals and Alloys.- Enhancement of Fatigue, Creep, and Stress Corrosion Resistance By Surface Treatments.- Microcutting: A Method to Study Surface Plasticity at Very High Strain Rates.- Surface Effects in Crystal Plasticity: Concluding Summary Lecture.- List of Participants.