What is the meaning of alloy wheels?

Definition: - A wheel made from a special alloy is known as alloy wheels. Alloy wheel for a vehicle especially made of an alloy of Aluminium or magnesium (formerly).

Alloys are mixtures of a metal & other elements to provide greater strength over pure metals.

what are mag wheels ?

History

In earlier alloys are made from magnesium are known by name “Mag Wheels”. The mag wheels remained popular through 1960’s. By property mag wheels are very lighter than alloy wheels which is made from aluminium. Comparatively aluminium is cheaper than magnesium & mag wheels are not affordable to common vehicles. Magnesium is generally considered to be an unsuitable alloy for road usage due to its brittle nature and susceptibility to corrosion. (Flammability doesn't help either!). For this reason alloy wheels took the place of mag wheels as low cost & high performance wheels for motor sports.

How alloy wheels are made ?

Alloys are produced by generally two types

  1. Forging
  2. Casting

Forging

Forging can be done by a one or multi-step process forging from various magnesium alloys, Wheels produced by this method are usually of higher toughness and ductility than aluminium wheels, although the costs are much higher.

 

Casting

Casting is of three types

  1. High pressure die casting (HPDC)
  2. Low pressure die casting (LPDC)
  3. Gravity casting

High pressure die casting (HPDC)

This process uses a die arranged in a large machine that has high closing force to clamp the die closed. The molten magnesium is poured into a filler tube called a shot sleeve. A piston pushes the metal into the die with high speed and pressure, the magnesium solidifies and the die is opened and the wheel is released. Wheels produced by this method can offer reductions in price and improvements in corrosion resistance but they are less ductile and of lower strength due to athe nature of HPDC

Low pressure die casting (LPDC)

This process usually employs a steel die, it is arranged above the crucible filled with molten magnesium. Most commonly the crucible is sealed against the die and pressurized air/cover gas mix is used to force the molten metal up a straw-like filler tube into the die. When processed using best practice methods LPDC wheels can offer improvements in ductility over HPDC magnesium wheels and any cast aluminium wheels, they remain less ductile than forged magnesium.

Gravity casting

Gravity-cast magnesium wheels have been in production since the early 1920s and provide good ductility, and relative properties above what can be made with aluminium casting. Tooling costs for gravity-cast wheels are among the cheapest of any process. This has allowed small batch production, flexibility in design and short development time.