Mechanical Metallurgy is the study of how metals respond to mechanical forces and how their mechanical properties can be modified through processes like deformation, heat treatment, and alloying. It is critical in designing materials to withstand specific stresses and environments.
1. Plastic Deformation and Dislocation Theory
- Plastic Deformation.jpg (10.1 KiB) Viewed 1696 times
- Plastic Deformation: Permanent change in a material's shape under applied stress.
- Dislocations: Line defects in the crystal structure of metals that allow plastic deformation.
- Edge Dislocations: Extra plane of atoms.
- Screw Dislocations: Spiral misalignment of atoms.
- Understanding dislocation movement helps explain metal strength and hardness.
- Dislocation Theory.jpg (11.39 KiB) Viewed 1695 times
- Focuses on how materials crack and fail under stress.
- Brittle Fracture: Sudden failure with little deformation (e.g., ceramics, low-temperature metals).
- Ductile Fracture: Failure with significant plastic deformation.
- Concepts like stress intensity factor (K) and fracture toughness are used to predict failure.
- Fracture__Mechanics.jpg (8.39 KiB) Viewed 1694 times
- Occurs when materials fail under repeated cyclic loading, even below their yield strength.
- Fatigue life is affected by:
- Stress amplitude.
- Surface finish (crack initiation sites).
- Environmental factors (corrosion fatigue).
- S-N curves (stress vs. number of cycles) are used to estimate fatigue life.
- Time-dependent deformation of materials under constant stress, typically at high temperatures.
- Stages of creep:
- Primary Creep: Initial slow deformation.
- Secondary Creep: Steady deformation rate.
- Tertiary Creep: Accelerated deformation leading to failure.
- Applications: Design of turbine blades, boilers, and engines.
- Wear: Loss of material due to surface interactions.
- Adhesive Wear: Metal bonding between surfaces.
- Abrasive Wear: Hard particles remove material.
- Corrosive Wear: Combination of chemical attack and mechanical action.
- Studying wear helps in designing wear-resistant materials and coatings.
- Tensile Testing: Measures ultimate tensile strength (UTS), yield strength, and ductility.
- Hardness Testing: Resistance to deformation (Brinell, Rockwell, Vickers scales).
- Impact Testing: Evaluates toughness (Charpy and Izod tests).
- Creep and Fatigue Testing: Measures long-term behavior under stress and cyclic loading.
- Mechanical Metallurgy is crucial in industries like:
- Automotive (crash-resistant materials).
- Aerospace (lightweight and strong alloys).
- Construction (structural materials like steel and rebar).
- Energy (turbine blades, pipelines).