Intro to Materials Engineering

Introduction to Materials Engineering

• Materials engineering is the study of the properties of materials and their applications in engineering.

Historical Perspective

• The advancement of societies is linked to the development of materials.
• Early civilizations were often named based on the materials they used, such as the Stone Age.
• Historically significant materials include stone, wood, clay, skins, pottery, and various metals.
• Heat treatments and the addition of substances have been used to modify materials.
• Modern materials include metals, plastics, glasses, and fibers.
• Materials are crucial in automobiles and electronic devices.

Materials Science and Engineering

• Materials science investigates the relationships between the structures and properties of materials.
• Materials engineering involves designing the structure of a material to achieve specific properties.
• A key aspect of materials engineering is understanding structure-property correlations.

Structure and Properties

• Structure refers to the arrangement of a material's internal components.
• Property refers to how a material responds to an external stimulus.
• A specimen subjected to forces will experience deformation.
• A polished metal surface will reflect light.
• Properties can be mechanical, electrical, thermal, magnetic, optical, or deteriorative.

Levels of Material Structure

• Subatomic Level: Involves the electronic structure of individual atoms and their interactions, like interatomic bonding.
• Atomic Level: Focuses on the arrangement of atoms; different arrangements can yield different properties, as seen with graphite and diamond.
• Microscopic Structure: Deals with the arrangement of small grains of a material, typically observed with microscopy.
• Macroscopic Structure: Considers structural elements visible to the naked eye.

Properties of Materials

• Mechanical Property: Response to external force or load, leading to deformation.
• Electrical Property: Includes electrical conductivity, resistivity, and dielectric constant.
• Thermal Property: Refers to heat capacity or thermal conductivity at certain temperatures.
• Magnetic Property: describes how a material responds to a magnetic field.
• Optical Property: How a material interacts with electromagnetic radiation, determining transparency, translucency, or opacity.
• Deteriorative Property: A material's ability to withstand chemical reactivity with its environment, including corrosion and resistance.

Processing, Structure, Properties, and Performance

• Processing influences structure, which determines properties, ultimately affecting performance.

Why Study Materials Science and Engineering?

• Materials science is essential for solving design problems involving materials.
• Involves selecting the right material.
• Requires optimizing the combination of properties.
• Addresses potential deterioration during service.
• Considers economics.
• Understanding material characteristics, structure-property relationships, and processing techniques aids in making informed material choices.

Classification of Materials

• Materials can be classified into categories like:
  • Metals
  • Ceramics
  • Polymers
  • Composites
  • Semiconductors
  • Biomaterials
  • Nanomaterials
  • Smart materials

Metals

• Contain many non-localized electrons.
• They have good conductors of electricity and heat.
• They are not transparent to visible light.
• They are strong and deformable.
• Examples include steels, aluminum, and gold.

Ceramics

• Made of compounds between metallic and nonmetallic elements like oxides, nitrides, and carbides.
• Good insulators.
• They are resistant to high temperatures more than metals and polymers.
• Hard but brittle.
• Examples are clay minerals, cement, and glass.

Polymers

• Organic compounds based on carbon, hydrogen, and other non-metallic elements.
• Polymers have large molecular structures which usually give polymers low densities and flexibility.
• Examples include plastics and rubber.

Composites

• Engineered materials made of more than one material type.
• Designed to display a combination of the best characteristics of each component.
• An example is fiberglass, which combines strength from glass and flexibility from polymer.

Semiconductors

• Materials with electrical properties intermediate between conductors and insulators.
• Semiconductors are very sensitive to minute concentrations of impurity atoms.
• Examples: Si, Ge, GaAs

Density, Strength, and Other Properties

• Charts can be used to compare the density, strength, and resistance to fracture for metals, ceramics, polymers, and composites.

Biomaterials

• Used in components implanted in the human body to replace diseased or damaged parts.
• Must not produce toxic substances or cause adverse biological reactions.
• Examples consist of titanium alloy Ti-6Al-4V and MP35N (35% Co, 35% Ni, 20% Cr, 10% Mo by wt).

Materials of the Future: Smart Materials

• Also known as intelligent materials.
• Able to sense changes in their environments and respond in predetermined manners.
• Have sensors (detects and input signal) and actuator (performs a responsive and adaptive function.
• Sensor materials include shape-memory alloys, fiber optics, piezoelectric materials, and microelectromechanical(MEM) devices.
• Actuator materials include shape memory alloys, piezoelectric ceramics, magnetorestrictive materials and electrorheological/magnetorheological fluids.

Materials of the Future: Nanomaterials

• Nanotechnology studies materials with dimensions on the nanometer scale (10^-9 m).
• These materials are typically less than 100 nanometers in size.
• An example of a nanomaterial: carbon nanotube.

Equipment for Studying Materials

• Optical Microscope
• Scanning Electron Microscope
• Transmission Electron Microscope
• Scanning Probe Microscope

Environmental Impact of Materials

• Use of Nonrenewable resources like Polymers-oil+metal
• Can cause Pollution
• Mining Impacts
• Production of toxic chemicals
• Waste Disposal issues

Solutions to Environmental Impacts

• Discover additional reserves
• Development of new materials having comparable properties with less adverse environmental impact
• Increased recycling efforts
• Development of new recycling technologies
• Consider life cycle of materials from “cradle-to-grave"
• Roles that materials scientists and engineers play