Magnesium alloys are mixtures of magnesium with other metals (called an alloy), often aluminium, zinc, manganese, silicon,

copper, rare earths and zirconium. Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminum, copper and steel. Therefore magnesium alloys are typically used as cast alloys, but research of wrought alloys has been more extensive since 2003. Cast magnesium alloys are used for many components of modern cars, and magnesium block engines have been used in some high-performance vehicles; die-cast magnesium is also used for camera bodies and components in lenses. Magnox (alloy), whose name is an abbreviation for 'magnesium non-oxidising', is 99% magnesium and 1% aluminium, and used in the cladding of fuel rods in some nuclear power stations. Magnesium alloys tend to be referred to by short codes (defined in ASTM 275) denoting the approximate chemical composition by weight: for example, AS41 has 4% aluminium and 1% silicon; AZ81 is 7.5% aluminium and 0.7% zinc. If aluminium is present, manganese is almost always also there at about 0.2% by weight to improve grain structure; if aluminium and manganese are absent, zirconium is usually present at about 0.8% for the same purpose.

Designation
Magnesium alloys names are often given by two letters following by two numbers. Letters tells main alloying elements (A = aluminum, Z = zinc, M = manganese, S = silicon). Numbers tells nominal compositions of main alloying elements respectively. Marking AZ91 mean magnesium alloy where is roughly 9 weight percent aluminum and 1 weight percent zinc. Exact composition should be confirmed from the standards. Cast alloys

Magnesium casting proof stress is typically 75-200 MPa, tensile strength 135-285 MPa and elongation 2-10%. Typical density is 1800 kg/m3 and Young's modulus is 42 GPa
Wrought alloys

Magnesium wrought alloy proof stress is typically 160-240 MPa, tensile strength is 180-440 MPa and elongation is 7-40%.Wrought magnesium alloys have a special feature. Their compressive proof strength is smaller than tensile proof strength. After forming, wrought magnesium alloys have a stringy texture in the deformation direction, which increases the tensile proof strength. In compression the proof strength is smaller because of twinning, which happens more easily in compression than in tension in magnesium alloys because of the hexagonal lattice structure

Aluminium alloys with magnesium

Birmabright Magnalium

(codes: A=Aluminium C=Copper E=Rare earths, usually provided by adding mischmetal to the melt, H=Thorium K=Zirconium L=Lithium M=Manganese O=Silver S=Silicon T=Tin W=Yttrium Z=Zinc) The thorium-containing alloys tend not to be used since a thorium content of more than 2% means a component has to be handled as a radioactive material. Magnesium alloys are used for both cast and forged components, with the aluminum-containing alloys usually used for casting and the zirconium-containing ones for forgings; the zirconiumbased alloys can be used at higher temperatures and are popular in aerospace. Magnesium+yttrium+rare-earth+zirconium alloys such as WE54 and WE43 (the latter with composition Mg 93.6%, Y 4%, Nd 2.25%, 0.15% Zr) can operate without creep at up to 300C and are reasonably corrosion-resistant.

Titanium alloy
Titanium alloys are metallic materials which contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures), light weight, extraordinary corrosion resistance, and ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to military applications, aircraft, spacecraft, medical devices, connecting rods on expensive sports cars and some premium sports equipment and consumer electronics. Auto manufacturers Porsche and Ferrari also use titanium alloys in engine components due to its durable properties in these high stress engine environments. Although "commercially pure" titanium has acceptable mechanical properties and has been used for orthopedic and dental implants, for most applications titanium is alloyed with small amounts of aluminum and vanadium, typically 6% and 4% respectively, by weight. This mixture has a solid solubility which varies dramatically with temperature, allowing it to undergo precipitation strengthening. This heat treatment process is carried out after the alloy has been worked into its final shape but before it is put to use, allowing much easier fabrication of a high-strength product

Transition temperature
The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal phase with a c/a ratio of 1.587. At about 890C, the titanium undergoes an allotropic transformation to a body-centred cubic phase which remains stable to the melting temperature. Some alloying elements raise the alpha-to-beta transition temperature[1] (i.e., alpha stabilizers) while others lower the transition temperature (i.e., beta stabilizers). Aluminium, gallium,

germanium, carbon, oxygen and nitrogen are alpha stabilizers. Molybdenum, vanadium, tantalum, niobium, manganese, iron, chromium, cobalt, nickel, copper and silicon are beta stabilizers

Categories
Titanium Alloys are generally classified into four main categories:[3]

Alpha alloys which contain neutral alloying elements (such as tin) and/ or alpha stabilisers (such as aluminium or oxygen) only. These are not heat treatable. Near-alpha alloys contain small amount of ductile beta-phase. Besides alpha-phase stabilisers, near-alpha alloys are alloyed with 1-2% of beta phase stabilizers such as molybdenum, silicon or vanadium. Alpha & Beta Alloys, which are metastable and generally include some combination of both alpha and beta stabilisers, and which can be heat treated. Beta Alloys, which are metastable and which contain sufficient beta stabilisers (such as molybdenum, silicon and vanadium) to allow them to maintain the beta phase when quenched, and which can also be solution treated and aged to improve strength.

Properties
Generally, alpha-phase titanium is stronger yet less ductile and beta-phase titanium is more ductile. Alpha-beta-phase titanium has a mechanical property which is in between both. Titanium dioxide dissolves in the metal at high temperatures, and its formation is very energetic. These two factors mean that all titanium except the most carefully purified has a significant amount of dissolved oxygen, and so may be considered a Ti-O alloy. Oxide precipitates offer some strength (as discussed above), but are not very responsive to heat treatment and can substantially decrease the alloy's toughness. Many alloys also contain titanium as a minor additive, but since alloys are usually categorized according to which element forms the majority of the material, these are not usually considered to be "titanium alloys" as such. See the sub-article on titanium applications. Titanium alone is a strong, light metal. It is as strong as steel, but 45% lighter. It is also twice as strong as aluminium but only 60% heavier. Titanium is not easily corroded by sea water, and thus is used in propeller shafts, rigging and other parts of boats that are exposed to sea water. Titanium and its alloys are used in airplanes, missiles and rockets where strength, low weight and resistance to high temperatures are important. Further, since titanium does not react within the human body, it and its alloys are used to create artificial hips, pins for setting bones, and for other biological implants. See Titanium#Orthopedic_implants. A bearing is a machine element to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle.

The term "bearing" comes ultimately from the verb "to bear",[1] and a bearing is thus a machine element that allows one part to bear another, usually allowing (and controlling) relative motion between them. The simplest bearings are nothing more than surfaces cut or formed into a part, with some degree of control over the quality of the surface's form, size, surface roughness, and location (from a little control to a lot, depending on the application). Many other bearings are separate devices that are installed into the part or machine. The most sophisticated bearings, for the most demanding applications, are very expensive, highly precise devices, whose manufacture involves some of the highest technology known to human kind