intro to metals Flashcards
How much steel was produced worldwide in 2021?
Over 1.95 billion metric tonnes
Which country is the leading producer of steel?
China
What percentage of the world’s annual crude steel production did China account for between 2012 and 2019?
50%
Name the first structural use of cast iron.
Iron Bridge, Coalbrookdale, 1779
What significant structure was built with wrought iron in 1889?
The Eiffel Tower
What was the first major bridge built with wrought steel?
Firth of Forth Railroad Bridge, Scotland, 1890.
During which age was bronze, an alloy of copper and tin, predominantly used?
The Bronze Age
What marks the transition from the Bronze Age to the Iron Age?
The predominant use of iron for tools and weapons.
What do concrete and steel have in common?
Same thermal expansion
What is used for steel bridges?
High-strength galvanised steel
What is a metallic bond?
The force of attraction between free electrons and metal ions in metals
What is face-centered cubic (FCC) structure?
A crystal structure with an extra atom in the center of each face of the cubic unit
What are grain boundaries in metals?
Interfaces between adjacent crystalline regions with different orientations.
How are grain boundaries made more visible?
By etching with acid.
What is responsible for the plastic deformation of metals?
Dislocations
What does the presence of interstitial atoms indicate in an alloy?
Small atoms squeezed between larger atoms in the crystal lattice, affecting the alloy’s properties.
What is copper made?
Made from malachite
Why are pure metals not commonly used in commercial applications?
They are too soft due to dislocations and lack certain desired mechanical properties
What historical structure utilized 18,038 individual parts and 2.5 million rivets?
The Eiffel Tower
What are the properties affected by imperfections in metal crystals?
Mechanical properties such as strength and ductility
What is the significance of similar thermal expansion properties of concrete and steel in construction?
It prevents structural damage due to temperature variations
Why is steel considered the most important metal in construction?
Due to its volume of use and essential role in structural applications
What is the role of substitutional atoms in alloys?
They replace atoms in the crystal lattice, modifying the alloy’s properties
What are metalloids?
Intermediate metals
What can be said about metals and their melting and boiling points?
high
What is Hexagonal close packing?
A lattice structure which is able to achieve the highest packing density
What are examples of imperfection in crystals?
- Substitutional atoms
- Interstitial atoms
- Dislocations
- Vacancies
What are vacancies?
Missing atom in matrix
What is the yield stress in alloys like compared to pure metals?
Higher
What are substitutional atoms?
Atoms of a different size
When do grain boundaries occur?
You get grain boundaries as metal cools
How has the recycling of metals impacted the environment?
Recycling reduces the demand for raw material extraction, lowers energy consumption, and decreases greenhouse gas emissions, contributing to environmental sustainability
How do protective coatings enhance the longevity of metal structures?
Coatings such as galvanizing protect metals from corrosion, significantly extending their service life in harsh environments
Where are dislocations generated?
Dislocations are generated at stress concentrations or within the material at defects and grain boundaries
What are edge dislocation?
An edge dislocation occurs when an extra plane or layer of atoms extends part way into the crystal
What is involved in forming edge dislocations?
- The row of bonds will break and reattach itself to a different of atoms
- Change shape and structure
What determines yield stress?
Dislocation motion
What helps to stop dislocations?
Defects
What is an alloy?
An alloy is a metal mixed with other elements
How is the microstructure of an alloy determined?
Microstructure determined by processing techniques and
characterised by the size and shape of the grains of different phases, and their orientation and distribution
What is the microstructure of bronze?
Copper + 15% Tin alloy
What are the two categories of bronze you can have?
- Cast
- Cast and annealed
What is steel composed of?
Steel is an alloy of iron and carbon containing less than 2% carbon and 1% manganese
How man grades of steel are there currently?
3500
What are modern cars built with?
Modern cars built with new steels that stronger and up to 25% lighter
What is the first strengthening mechanism?
Control of grain size
What is the second strengthening mechanism?
Work Hardening
How does reducing grain size change yield stress?
Increases
What are the variables in the Hall-Petch equation?
- yield stress
- d = grain size
- k material constant
What is the process of work hardening?
- Dislocations have an associated strain field
- These interact creating a barrier to dislocation motion
What does increased dislocation density lead to?
Increased interaction and higher strength
When do dislocation increase in density?
Dislocations, increase in density during plastic flow
What is the 3rd strengthening mechanism?
Solid solution strengthening
How does solid solution strengthening work?
- Solute atoms have an associated strain field
- These interact with the strain field around dislocations and inhibits motion
What is quenching?
- Rapid cooling
What is the fourth strengthening mechanism?
Precipitation strengthening/hardening
How does Precipitation strengthening/hardening work?
Second phase particles have an associated strain field that interacts with that of dislocations and makes it harder for the dislocation to move
What is yield stress defined as?
Lower yield point
What do phase diagrams show?
- Which phases are present
- Temperatures and compositions
What do phase diagrams assume?
Equilibrium conditions
