WELLCOME

1
WELLCOME

• MAGNESIUM

A favorable strength-to-weight ratio makes
magnesium a desirable material for automotive
and aerospace parts
2

• New interest in magnesium has been recently
  aroused due to the expansion of use of magnesium
  alloys in the 1990s and, especially, due to an
  appearance of high-strength magnesium matrix
  composites as lightweight advanced structural
  materials for automotive and aerospace. Magnesium
  alloys are considered as possible replacements
  for aluminum, plastics, and steels, primarily
  because of their higher ductility, greater
  toughness, and better castability.

3

• Production of magnesium almost tripled last
  decade, and the world production capacity reached
  515,000 tons per year in 2009 . Both the
  increased production of magnesium and
  applications of new high-performance magnesium
  alloys have posed a scientific and technical
  challenge to the brazing engineering community.

4
Characterization of Base Metals

• Magnesium is the eighth most abundant element and
  constitutes about 2 of the Earth's crust, and it
  is the third most plentiful element dissolved in
  seawater. 
• Although magnesium is found in over 60
  minerals, only dolomite, magnesite, brucite,
  carnallite, and olivine are of commercial
  importance. 

• Magnesium and other magnesium compounds are also
  produced from seawater, well and lake brines and
  bitterns. 

5

• Magnesium is the lightest and one of the
  cheapest structural metals. Magnesium alloys are
  environmentally friendly, lighter than aluminum
  (only 2/3 of aluminum and 1/3 of titanium
  specific weights), better in heat dissipation and
  heat transfer due to high thermal conductivity of
  51 W/mK, and exhibit excellent ability in
  shielding electromagnetic interruption.

6

• Low density, 1.75 g/cm3, in combination with A
  relatively a high tensile strength  of 228290
  MPa, heat resistance up to (450C), and oxidation
  resistance up to 500C make magnesium alloys
  attractive for various structures in the
  automotive industries.

7

• Especially, the magnesium alloys are attractive
  for various aerospace industries, as well as in
  textile and printing machines where lightweight
  magnesium parts are used to minimize inertial
  forces  at high speed . Moreover, magnesium
  alloys are recyclable, which minimizes their
  environmental impact. However, the surface of
  magnesium alloys should be protected because they
  corrode easily when exposed to atmosphere.

8

• Mechanical properties (especially plasticity) of
  magnesium Alloys depend on the fabrication
  parameters and the testing temperature. For
  example, a considerable change in mechanical
  properties was observed for Alloy AZ31 fabricated
  by casting, extrusion, and rolling .
• The strength weakening is accompanied by a
  remarkable increase in ductility. The elongation
  increased from 21.5 to 66.5 as the test
  temperature changed from RT to 250C.

9

• Magnesium alloys with reduced aluminum content
  AM60, AM50, and AM20 are suitable for
  applications requiring improved fracture
  toughness. However, the reduction in aluminum
  results in a slight decrease in strength for AM
  alloys .
• Alloys AS41, AS21, and AE42 are employed for
  applications requiring long-term exposure at
  temperatures above 120C and creep
  resistance.   

10

• Magnesium compounds, primarily magnesium
  oxide, are used mainly as refractory material in
  furnace linings for producing iron and steel,
  nonferrous metals, glass, and cement. 
• Magnesium oxide and other compounds also are
  used in agricultural, chemical, and construction
  industries. 
• Magnesium alloys also are used as structural
  components of machinery. 
• Magnesium also is used to remove sulfur from iron
  and steel.

11
Magnesium Alloy WireThe highly accurate
magnesium alloy wire is 20 percent stronger than
extruded magnesium bar, which can be bent and
coiled at the room temperature. SEI' magnesium
alloy wire is high specific strength. Tensile
Strength  1.2 - 1.6 times (vs. Extruded)1.3 -
1.8 times (vs. Die Cast) 0.2 Proof Stress  1.4
- 2.0 times (vs. Extruded)1.6 - 2.5 times (vs.
Die Cast)Tolerance of dimensional accuracy is
lt1/100mm.

• Magnesium Alloy Tube
• The technology of wiredrawing skill would be used
  to produce for magnesium alloy tube. Mechanical
  properties of pipe are further more improved than
  conventional method. Tensile Strength  270MPa  A
  chieved 
•   Dimensional Accuracy  /-0.1mm  Achieved  
• Linearity Error  1mm/m  Achieved 
•   Bending Formability  2.8D  Almost Achieved  

12
Let us summarize !

• Magnesium is the third most commonly used
  structural metal, following Fe and Al.
• The main applications of Mg are in order
• component of aluminium alloys
• in die-casting (alloyed with Zn)
• to remove S in the production of iron and steel
• the production of titanium in the Kroll process.

13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
Microstructures and Macrostructures

• Optical micrograph Mg-Zn-Zr-(RE) alloy, cast and
  aged (no soln treatment).
• Note coarse gb ppts. Electron micrograph
  Mg-Nd-Zr alloy, cast, soln treated and aged to
  peak hardness. (Note PFZ at gbs) Mg-Zr-Zn-(RE)
  helicopter gearbox casing Bicycle frame (alloy
  unspecified ! 6 additives)

17
Magnesium alloy cast parts are gaining
increasing attention from the automotive sector
where the aim is weight reduction. However, the
casting of magnesium alloys is still plagued with
problems that are difficult to solve porosity,
macrosegregation, oxide entrainment, irregularity
of microstructure, corrosion, machining safety,
etc.
The following figure shows that SEM image of
oxide films on two opposite sides of a fracture
surface of a tensile test specimen taken from
AZ91 sample.
18

Some magnesium matrix composites exhibited
impressive increases in mechanical performance in
contrast with nonreinforced matrix alloys. For
example, the composite consisting of Mg-14Li-1Al
matrix and 30 vol- of steel fibers has a tensile
strength 600700 MPa at room temperature and
450480 MPa at 200C, while the matrix alloy
exhibits only 144 MPa at room temperature, and 14
MPa at 200C.
19
Magnesium matrix composites
20

• Advanced Mg-based materials have great potential
  to improve mechanical performance. New
  nontraditional reinforcing systems reach strength
  characteristics comparable with some steels or
  titanium alloys.
• For instance, the squeeze-casting composite of
  the matrix AZ91D alloy reinforced with 10 vol-
  of Al18B4O33 particles exhibits a tensile
  strength 480 MPa .

21

• Even the low-alloyed magnesium matrix MB15
  reinforced with 30 vol- of Al18B4O33 whiskers
  demonstrates a yield strength of 230 MPa and
  very good rigidity characterized with Youngs
  modulus 76 GPa and  0.5 elongation. An increase
  in volume fraction of the reinforcing component
  can result in drastic change of mechanical
  properties.
• The Swiss company EMPA  recently reported about
  the super-strength composite MgAl1/T300
  containing 60 vol- of graphite fibers. This
  material exhibited tensile strength of 1470 MPa
  and Youngs modulus 155 GPa.

For example
22

• Magnesium matrix composites also have potential
  for high-damping to reduce mechanical vibrations.
  For example, undirectional solidification of
  Mg-2Si alloy yields Mg/Mg2Si composite structure
  with a mechanical strength as high as the
  industrial cast Alloy AZ63 but with a damping
  capacity 100 times higher .

• A similar Mg-10Ni alloy with Mg/Mg2Ni structure
  provides a damping capacity 40 times higher than
  that of AZ63 cast. Moreover, Mg-2Si alloy
  reinforced with long carbon fibers has a Youngs
  modulus of 200 GPa with a damping capacity of
  0.01 for strain amplitude of 105.

23

• Due to the low solidus limitation of the matrix,
  only low-temperature filler metals such as P380Mg
  and P430Mg can be used for joining casting
  composites based on ZK51A and QE22A matrix
  alloys, or forged composites based on ZK60A and
  ZC71 matrix alloys.
• Joining other cast or forged composites can be
  performed by placing filler metal GA432 or P380Mg
  between the brazed parts and heating to
  390400C thoroughly controlling temperature.
  Joining of wrought  magnesium composites based on
  Mg-Zn matrixes is preferably carried out by
  soldering with Zn-Al solders.

24

• Creep-resistant alloys Mg-Al-Ca-Sn and
  Mg-Al-Ca-Zn were recently developed , and they
  showed yield strengths of 190203 MPa, ultimate
  tensile strengths of 240250 MPa, and elongations
  of 35 at room temperature.
• The minimum creep rate was less than 0.9 x 109
  s1 at 200C under loading of 55 MPa. Similar
  improvement of creep resistance was also measured
  for the Ca-added Mg-Al-Mn Alloy AM60B. It showed
  at least 10 times lower creep rate at 200C at
  the load of 90 MPa than Ca-free cast alloy.

25

• Experiments with composite Mg-based filler metals
  were recently started and will be finished in the
  near future to respond to strength requirements
  of new high-strength base materials such as
  magnesium matrix composites. Filler metal matrix
  reinforced with fine ceramic particles can
  increase yield strength in brazed joints  by at
  least 20 and creep strength by 5070 .

26

• The Mg-Al-Li system,  which has a eutectic
  Mg-36.4Al-6.6Li (wt-) composition at 418C ,
  looks like a possible candidate in the liquid
  phase to prepare and test for composite brazing
  filler metals. There are also other low-melting
  Mg-based alloys that might have good plasticity
  in solid state.

27

• Another alloy of this system Mg-8Li-5Al-1Zn is a
  filler metal with a melting point around 560C.
  This alloy demonstrates an unusually high tensile
  strength of 220 MPa after age hardening.
  Supposedly, the strength can be further increased
  by adding a small amount of zirconium.   

28
Typical Applications for Magnesium Alloys

• The use of magnesium alloys in car design is
  expanding, and now includes ultralightweight
  matrix composites. Typical automotive
  applications are engine blocks, cylinder liners,
  pushrods, valve spring retainers, instrument
  panels, clutch and brake pedal support brackets,
  steering column lock housings, and transmission
  housings .

29
Joining of magnesium alloys!

• Material-handling equipment and commercial
  applications include parts for magnesium
  dockboards, grain shovels,gravity conveyors,
  luggage, computer housings, digital camera
  housings, electrical conductors, and hand-held
  tools.
• In the aerospace industry, lightweight and stiff
  magnesium alloys are employed in various units
  and devices, for example, aircraft transmission
  systems and their auxiliary components, gear
  housings, rotor housings, and generator housings
  in cold areas of engines.
• In audio, video, computer, and communication
  equipment, plastics are being replaced by
  magnesium alloys that have advantages in
  strength, heat sink, and service life.
  Consequently, thin magnesium net shapes are used
  now in many models of cellular phones, laptop
  computers, and camcorders.

30
Thank you!