Engineering Materials Overview

Engineering Materials

• Materials are classified by nature into metals, ceramics, polymers, and composites.
• Classification is based on chemical composition, natural occurrence, refining/manufacturing process, atomic/crystalline structure, and industrial/technical application.

Metals and Alloys

• Inorganic materials composed of one or more metallic elements, potentially including non-metallic elements.

• Metals readily lose electrons, forming metallic bonds, and are good conductors of electricity.

• Properties include: electrical/thermal conductivity, solid state at ordinary temperatures, malleability, ductility, luster, sound production upon striking, alloy formation.

• Alloys form when multiple pure metals combine, creating new properties distinct from the individual components.

• Pure Metals: Obtained by refining ore; rarely used in engineering due to limited applications. Exception includes specialized use with high purity requirements (e.g., aluminum, copper).

• Alloyed Metals: Combination of two or more metals. Properties often greatly differ from constituent metals (e.g., 18-8 stainless steel, varying carbon content in steel).

• Ferrous Metals: Contain significant iron; crucial in engineering.

  • Mild Steels: 0.15%-0.25% carbon; moderate strength, good weldability, low cost.
  • Medium Carbon Steels: 0.3%-0.6% carbon; high strength, limited weldability.
  • High Carbon Steels: 0.65%-1.5% carbon; hardened and toughened by heat treatment, poor weldability.
  • Cast Irons: 2%-4% carbon; low cost; used in casting applications.

• Non-Ferrous Metals: Seven main metals (aluminum, tin, copper, nickel, zinc, and magnesium) readily available and economical. Additional less common high-demand metals exist.

• Sintered Metals: Created through powder metallurgy; mixed powders are molded and heated to bond, resulting in distinctly different properties from their component metals.

• Clad Metals: Two metallic layers bonded together (e.g., stainless steel clad with mild steel); layered materials offer combined properties.

Ceramics

• Inorganic materials made of metallic and non-metallic elements bonded chemically.
• Characteristics include high melting points, chemical stability, hardness, high-temperature strength (but are brittle), poor electrical conductivity.

Polymers

• Organic materials consisting of long carbon-based molecular chains or networks.
• Generally low density, mechanically flexible, variable mechanical properties, and poor electrical conductors.

Composites

• Mixtures of two or more materials; components retain distinct natures.
• Offer benefits such as: light weight, high strength, corrosion resistance, high strength-to-weight ratio, directional strength, high impact strength, and high electrical strength (insulator).

Semi-Conductors

• Materials intermediate between conductors and insulators in electrical properties.
• Electrical characteristics are sensitive to impurity atoms.
• Crucial component in the electronics industry (e.g., integrated circuits).

Smart Materials

• Materials with adaptable properties responsive to external stimuli (e.g., temperature, electric/magnetic fields).
• Combines sensor, actuator, and control circuit in one unit, emulating biological systems (e.g., MEMS).

Nano-Structured Materials and Nanotechnology

• Materials with structures ranging from 1-100 nm.
• Novel properties (e.g., electrical, optical, magnetic).
• Applications in various fields (e.g., medicine, energy, water filtration).
• Nanomaterials include quantum dots, nanoparticles, nanocrystals.

Importance of Materials

• Material development follows various approaches (from serendipity to design).
• Advanced materials, used in high-tech applications, are either enhanced traditional materials or newly developed high-performance materials.
• Current trends include high-temperature/corrosion-resistant materials, new metals, improved fatigue properties and various types of plastic composites.