Metal Ch. 5, 6, 7

A process by which a matter is transported through another matter

Diffusion

Can be effected by the Types of Diffusion, Temperature, Crystal structure, crystal imperfection, and concentration of diffusion

Diffusivity

Methods include Hardfacing, Coating, Selective Hardening Method, and Diffusion Methods

Case Harening

Examples of Hardfacing

Fusion and Thermal Spray

Examples of Coating

Electrochemical Plating, Thin Films, and Diamond Like Carbon

Examples of Selective Hardening Methods

Flame, Induction, Electron Beam, and Laser

Examples of Diffusion Methods

Carburizing and Nitriding

Creates a hardening wear resistant surface. Uses high temperatures, but has possible distortion

Diffusion Carburizing

Creates a hardening wear-resistance surface. Uses lower temperatures, near-zero distortion, and better corrosion resistance. However, its very time-consuming.

Diffusion Nitriding

Sheets and plates produced from ingots by rolling

Wrought

Ingots are preheated and rolled, resulting in the greater reduciton of thickness in a single pass

Hot Rolling

Ingots rolled room temp, resulting in tight tolerance on surface finish, dimensions, and hardness. But can cause more strain

Cold Rolling

Metal under high pressure is force through opening in a die

Extrusion

Starting rod or wire is drawn though several drawing dies to reduce diameter

Wire Drawing

Used to shape cup like articles from flats and sheets of metals

Deep Drawing

Metal, usually hot, is hammered or pressed into desired shape. Incraes structural properties, removes porosity and increase homogeneity

Forging

Dies are flat and simple in shape

Open Die Forging

Dies have upper and lower impresion

Closed Die Forging

Causes metal to undergo deformation

Uniaxial Tensile Force

Metal returns to its original dimension after tensile force is removed

Elastic Deformation

The metal is deformed to such an extent such that it cannot return to its original dimension

Plastic Deformation

Strenght of material can be tested by pulling the metal to failure

Tensile Test

Strenght at which metal or alloy show significant amount of plastic deformation. Includes a 0.2% offset

Yield Strength

The maximum strength reached by the engineering stress strain curves

Ultimate Tensile Strenght (UTS)

A measure of ductility of a meterial

Percent Elongation

Also known as the measure of ductility

Percent Reduction in Area

The measure of the resistance of a metal to permanent (Plastic) deformation

Hardness

Plastic Deformation of single crystal results in step marking on surface

Slip Bands

A part of atomic lattice is deformed and forms mirror image of lattice next to it

Twinning

Stops dislocation movement and hence strenghten the metals

Effects of Grain Boundaries

Reheating metals resulting in the softening of the part through recovery, recystallization, and grain growth.

Annealing

Decreases tensile strength but increases ductility

Effects of Annealing

High plastic deformaiton and slow crack

Ductile Fracture

No significant plastic deformation before fracture

Brittle Fracture

Defects like Folds, Undesirable grain flow, Porsoity, Tears and Cracks, Corrosion damge, and Embirittlement

Causes of Brittle Fracture

A measure of energy absorbed before failure/fracture

Toughness and Impact Test

Cracks and Flaws

Causes Stress Concentration

Allow one to preduct if a component will be able to be used for its intended fuction even if it has a defect

Fracture Toughness

Cyclinc (Repetitve) loads causing an eventual failure

Fatigue Failure

Stress concentraiton, surface roughness, surface condition, and environment all

Affects Fatique Strength

Progressive deformation under constant stress

Creep

Determines the effect of temperature and stress on creep rate

Creep Test