Metallurgical consultant


Material Selection

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Selecting an appropriate material is a critical part of almost all engineering designs. Factors to consider


Young's Modulus       Density      Strength         Ductility


Toughness    Stiffness     Electrical Resistivity       Corrosion   Cost

 

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Comparative Application of Metallic Materials

Metallic Materials

Aluminium alloys

 

 

 

 

 

 

 

 

 

 

Mild steel


 

 

 

 

 

 

 

 

 

 

 

Cast iron

 

 

 

 

 

 

 

 

 

 

 

 

 

Stainless steels









Brasses

 

 

 

 

 

Nickel alloys

 

 

 

 

 

 

 

 

Titanium alloys

Overview


Low strength and high ductility (ideal for foil).

Strength is increased by alloying,with Si, Mg, Cu, Zn, and heat treatment.

Quite reactive, but protects itself thin oxide layer. surface can be "anodised", to resist corrosion and to give decorative effects.


 Most important engineering materials,

with range of strength & ductility, by cold working, heat treatment & C%

high density and Young's modulus,cheap, strong used for construction, transport and packaging.

It is inherently very tough. rusts easily, and protected by

painting, galvanising or other coatings.


Forerunners to steels, being iron alloys of high carbon content (2-4%).

cheap, moderate strength easily be cast to shape.

high density and Young's modulus poor toughness, strength and toughness improved by alloying and heat treatment.

Cast irons rust easily, protected by painting or other coatings.


Most important engineering materials, cover a wide range of alloys based on iron and carbon. more expensive steels containing typically high % of Cr and Ni, gives excellent corrosion resistance, high strength, toughness , Young's modulus. The strength and toughness of stainless steels can be varied by alloying, working and heat treatment


Quite expensive alloys of copper and zinc.

working and heat treatment give better t with good corrosion resistance.


Pure nickel has moderate strength, Alloying with Cr, Co, Mo, Dense, stiff, strong alloys used primarily for their strength and corrosion resistance at high temperatures

Nickel is also alloyed with copper to make coins.


reactive metal when hot, but has good corrosion resistance at room temperature. inert in the body, Pure titanium has moderate strength, alloy contains 6% aluminium and 4% vanadium, gives the high strength , low density, stiff, strong alloys, expensive

Design Issues


High strength-to-weight ratio

High stiffness-to-weight ratio


High electrical and thermal conductivity


Easy to shape Easy to recycle

Difficult to arc weld


 High strength-to-weight ratio

High stiffness-to-weight ratio

Good strength with high toughness

 High stiffness

 Very cheap

 Easy to shape

  Easy to weld

   High density

Poor electrical & thermal conductivity



High strength with good toughness

High stiffness

Mostly very cheap

Easy to weld

Easy to recycle

Easy to machine

High density

Poor electrical and thermal conductivity





High strength with good toughness

 High stiffness

  Mostly very cheap

 Quite easy to shape

  Quite easy to weld, but not as easy as for carbon steels.

    High density

  Poor electrical and thermal conductivity







Reasonable strength

Corrosion resistant

Easy to shape

Quite expensive




High strength at high temperature

High corrosion resistance

High stiffness

Easy to shape

High density





High strength, even at high temperatures

High stiffness

Chemically inert in body 

High cost

Chemically very reactive when hot

Quite difficult to shape - usually cast

Typical Products

 

Aircraft

Bicycles

Car engines

"Space frame"

car bodies

Drinks cans

Window frames

 

 

 

 

 

Large structures - bridges, buildings, oil rigs

Car body panels, trains

Machine tools

Pressure vessels

Food packaging

Nails

 

 

 

 

 

Car engines

Brake discs

Machine tools

 

 

 

 

 

 

 

 

 

 

 

Bearings

Pressure vessels

chemical plant

Cutlery

Surgical instruments

 

 

 

 

 

 

 

 

 

 

Ornamental fittings

Plumbing fittings

Screws

Bullets

 

 

Jet engines for aircraft

Coins

Tanks for chemicals

 

 

 

 

Fan blades for aircraft jet engines

Hip replacements, and other medical implants

sports products

jet engine.