Understanding Materials: Properties, Types, and Treatments

Material Classification

Natural Materials

These materials are obtained directly from nature, such as:

• Wood
• Coal
• Metal
• Stone

Artificial Materials

These materials are derived from natural materials through processing, such as:

• Glass
• Paper
• Cement

Synthetic Materials

These materials are created through chemical reactions involving artificial materials, such as:

• Plastics

Material Types and Their Properties

Ceramics

Ceramics exhibit the following properties:

• Fragility
• Low thermal conductivity
• Low electrical conductivity
• Hardness
• Brittleness

Metallic Materials

Metals possess these characteristics:

• High electrical and thermal conductivity
• Resistance
• Ductility
• Malleability
• Ability to form alloys with other elements to enhance properties

Plastics/Polyesters

Plastics and polyesters typically have these properties:

• Low electrical and thermal conductivity (insulators)
• Low resistance
• Toughness

Physical Properties of Materials

Extension: The ability of a material to occupy space.

Impenetrability: The resistance of a material to being occupied by another material.

Density: The ratio of a material's mass to its volume.

Specific Volume: The ratio of a material's volume to its mass.

Specific Weight: The ratio of a material's weight to its volume.

Resistivity: The resistance of a material to the flow of electric current.

Conductivity: The ability of a material to conduct electric current. Types of conductivity include:

• Conductors: Materials with low resistivity, allowing current to flow easily.
• Insulators: Materials with very low conductivity, hindering current flow.
• Semiconductors: Materials whose conductivity depends on temperature, with two types: low (acting as insulators) and high (acting as conductors).
• Superconductors: Materials that exhibit perfect conductivity at low temperatures, with no energy loss as heat.

Chemical Properties of Materials

Oxidation: Occurs in dry environments, leading to the formation of oxides on the material's surface.

Corrosion: Occurs in wet environments, causing the material to degrade.

Metals and Alloys

Alloys: Combinations of metals that improve material properties.

Base Element: The element present in the highest proportion in an alloy.

Alloying Element: The element present in a lower proportion in an alloy.

Example: Bronze is an alloy composed of 88% copper (base element) and 12% tin (alloying element).

Material Treatments

1. Thermal Treatments

Annealing:

Process:

1. Heat the material.
2. Maintain the elevated temperature for a specific duration.
3. Slowly cool the material within a furnace.

Result: Increased toughness and ductility, making the material easier to machine, but with reduced hardness.

Normalizing: Similar to annealing, but with a faster cooling process at room temperature, resulting in slightly less hardness than annealing.

Hardening:

Process:

1. Heat the material to a high temperature.
2. Rapidly cool the material.

Result: A very hard material, but with increased fragility.

Tempering:

Process:

1. Applied only after hardening.
2. Heat the material to a lower temperature than used in hardening.
3. Cool the material rapidly.

Result: Improved stability and toughness, but with slightly reduced hardness compared to hardened material.

2. Thermochemical Treatments

These treatments increase hardness without compromising toughness, wear resistance, or corrosion resistance.

Cementation: Adding carbon to the metal surface, enhancing hardness and resistance to friction.

Nitriding: Adding nitrogen to the surface, improving wear resistance, often used for saws and drills.

Cyanuration: Combining nitriding and cementation (carbon + nitrogen), typically applied to steel.

Sulfurization: Adding sulfur, nitrogen, and carbon, resulting in the highest hardness and resistance to wear and corrosion.

3. Mechanical Treatments

These treatments involve deforming metals to improve their structure and eliminate fissures and cavities.

Cold Working: Performed at room temperature, including processes like lamination, stamping, stretching, and cold drawing.

Hot Working: Performed at elevated temperatures, often used for manufacturing tools and crafts, and includes processes like lamination, forging, stamping, and extrusion.

Mechanical Properties of Materials

Cohesion: The resistance of molecules within a material to being separated.

Hardness: The resistance of a material to being scratched or penetrated by another material.

Elasticity: The ability of a material to return to its original shape after the deforming force is removed.

Plasticity: The ability of a material to deform permanently without breaking.

Fragility: The opposite of toughness; the tendency of a material to break into pieces easily.

Toughness: The ability of a material to absorb energy before breaking.

Ductility: The ability of a material to be drawn into thin wires.

Malleability: The ability of a material to be hammered or rolled into thin sheets.

Flexibility: The ability of a material to bend without breaking.

Fatigue: The failure of a material due to repeated or continuous stress.

Resilience: The ability of a material to absorb energy and return to its original shape after deformation.

Machinability: The ease with which a material can be machined or shaped.