Materials

Why do engineers need to understand materials?

To select appropriate materials and processing techniques by understanding material properties and the structure–property relationship.

What is materials science?

The study of the relationship between a material's structure and its properties, including the development of new materials.

What is materials engineering?

Applying existing materials and processing techniques to manufacture products.

Why are materials important?

Materials drive technological advancement.
Examples:

• Stone Age

• Bronze Age

• Iron Age

• Modern ages (Silicon, Nanomaterials, Polymers, Sustainable Materials)

What determines a material's properties?

Its structure.

Processing changes structure, and structure determines properties.

Complete the relationship:

Processing → _____ → Properties

Structure

Name the four major classes of engineering materials.

• Metals

• Polymers

• Ceramics

• Composites

Characteristics of metals?

• Strong

• Ductile

• High electrical conductivity

• High thermal conductivity

• Reflective

Characteristics of polymers?

• Low density

• Soft

• Ductile

• Poor electrical conductor

• Poor thermal conductor

Characteristics of ceramics?

• Hard

• Brittle

• Poor electrical conductor

• Poor thermal conductor

• High temperature resistance

What is a composite?

A material made by combining two or more materials to improve performance.

What are the three steps of material selection?

• Determine required properties

• Select candidate materials

  • Select processing technique

What property categories do engineers consider during material selection?

• Mechanical

• Electrical

• Thermal

• Magnetic

• Optical

• Deteriorative

What are the six material property categories?

• Mechanical

• Electrical

• Thermal

• Magnetic

• Optical

• Deteriorative

What happens to steel hardness as carbon content increases?

Hardness increases.

Increasing temperature has what effect on electrical resistivity?

Electrical resistivity increases.

Increasing impurity content in copper has what effect on resistivity?

Resistivity increases.

Increasing impurity content has what effect on thermal conductivity?

Thermal conductivity decreases.

Why are porous ceramics good insulators?

Because the air voids greatly reduce heat transfer.

What is one of an engineer's most important responsibilities?

Selecting the most appropriate material and manufacturing process for an application.

In general, rank material density from highest to lowest.

Metals > Ceramics > Polymers

Examples of composites?

• Polymer Matrix Composites (PMCs)

• Metal Matrix Composites (MMCs)

• Ceramic Matrix Composites (CMCs)

Examples of polymers?

• Polyethylene

• Epoxy

• Phenolics

Examples of ceramics?

• Glass

• Silicon carbide

• Bricks

Examples of metals?

• Steel

• Aluminium

• Copper

• Magnesium

• Zinc

List the requirements for an artificial hip replacement material.

• Biocompatible

• Chemically inert

• High strength

• Wear resistant

• Good lubricity

How can stress corrosion cracking be reduced?

Heat treatment.

What is stress corrosion cracking?

Cracking caused by the combined effects of tensile stress and a corrosive environment.

What affects the optical properties of materials?

Their structure.

How can magnetic permeability of iron be improved?

Adding approximately 3 atomic % silicon (Si) to iron increases its magnetic permeability, making it a better magnetic recording material.