Magnesium and-its-alloys, structures, properties, effects of alloying, applications
- 1. MAGNESIUM AND ITS ALLOYS MOIZ ULLAH BAIG (MM-036) SAAD ARIF (MM-026) HARIS IQBAL KHAN (MM-020) OMAR SIDDIQI (MM-004)
- 3. DISCOVERY • In 1755 • By Joseph Black • At Edinburgh, England • Name derived from Greek word ‘Magnesia’ • About 2.4% of the Earth’s crust contains Magnesium making it the 6th most abundant element.
- 4. ATOMIC STRUCTURE Atomic Number: 12 Atomic Mass: 24 Group: Alkaline Earth Metal Configuration: 1s2, 2s2, 2p6, 3s2
- 5. PROPERTIES • Color: Silvery white metal • Phase: Solid • Crystalline Structure: Hexagonal • Melting Point: 651 °C • Boiling point: 1100°C • Specific Gravity: 1.74 gm/cm3 • Burns in air with a bright white light.
- 6. APPLICATIONS • Aircraft and missile industries • Photo-engraving • Deoxidizer and desulfurizer in the manufacture of nickel and copper alloys • Magnesium anodes provide effective corrosion protection • Automotive wheels, housings, transmission cases • Bicycles and other sporting goods equipment • Laptops, televisions, cell phones
- 7. MAGNESIUM ALLOYS • Metal for the 21st century. • Alloying is used to improve the formability of magnesium • Most versatile material choices amongst the structural materials. • High strength-to-weight ratio.
- 8. ALLOY DESIGNATION • The letters stand for the two major alloying elements, - first letter is the highest amount. - second letter is the second highest amount. • The numbers stand for the amount of the two major alloying elements, - first number following the letters stands for the wt.% of the first letter element. - second number stands for the wt.% of the second letter element.
- 10. Alloying Element Effects of Addition Aluminum (Al) Increases hardness, strength, and castability while only increasing density minimally. Calcium (Ca) Improves thermal and mechanical properties as well as assists in grain refinement and creep resistance. Also, it reduces surface tension. Cerium (Ce) Improves corrosion resistance. Also, it increases plastic deformation capability, magnesium elongation, and work hardening rates. But it reduces yield strength. Copper (Cu) Assists in increasing both room and high temperature strength. Manganese (Mn) Increases saltwater corrosion resistance within some aluminum containing alloys. Nickel (Ni) Increases both yield and ultimate strength at room temperature. Negatively impacts ductility and corrosion resistance. Strontium (Sr) Used in conjunction with other elements to enhance creep performance. Tin (Sn) When used with aluminum it improves ductility and reduces tendency to crack during processing. Yttrium (Y) Enhances high temperature strength and creep performance when combined with other rare earth metals. Zinc (Zn) Increases the alloys fluidity in casting. When added to magnesium alloys with nickel and iron impurities, it can improve corrosion EFFECTS OF ALLOYING ELEMENTS
- 11. MAGNESIUM-ALUMINUM BINARY ALLOY SYSTEM • Increases hardness • Improves strength • Slightly increases density
- 12. MAGNESIUM-ALUMINUM BINARY PHASE DIAGRAM Liquid Fcc-Al Mg-Hcp 0.31 0.12 0.84 1 0.8 0.6 0.4 0.2 0 300 400 500 600 700 800 900 1000 𝛾 = Al 12 Mg 17 +𝛾 Mg-Hcp Fcc-Al + Al 140 Mg 89 723 K 732 K 705 K Mole fraction (Al) 683 K 𝛾
- 13. SCHEMATIC VIEW OF EUTECTIC MICROSTRUCTURE OF MG-AL ALLOY • Primary α-Mg Pure Mg Dendrites • Intermetallic phase β-phase i.e. Mg17Al12
- 14. MAGNESIUM-ALUMINUM GRAIN SIZES (a) Mg-1%Al (b) Mg-5%Al (c) Mg-6%Al (d) Mg-9%Al Grain sizes of binary Mg-Al Alloys HV: 15kv 20.5 µ m HV: 15kv 20.5 µ m HV: 15kv 20.5 µ m HV: 15kv 20.5 µ m • Reduces grain size and improves ultimate tensile and yield strength
- 15. EFFECT OF STRONTIUM ADDITION• Distributed along the grain boundaries • Lamellar structure formed • Better creep resistance can be obtained SEM photos of the as-cast alloys. (a) AJC411and
- 16. (a) AJC411 (b) AJC511
- 17. MAGNESIUM-ZINC BINARY ALLOY SYSTEM • Have a strong age hardening response. • Heat-treatable high strength can be potentially developed.
- 19. MAGNESIUM ZINC GRAIN SIZES Grain sizes of binary Mg-Zn alloys, (a) 0.2 at.%, (b) 0.7 at.% (a) (b) • Reduces with increase in concentration of Zinc (Zn)
- 20. EFFECT OF ZIRCONIA ADDITION ON GRAIN SIZE • Enhances the homogeneity by making the grains round • Reducing the amount of eutectic at the grain boundaries • Contribute positively to the strength of the alloy
- 21. CORROSION RESISTANCE • Depends upon, 1) The alloying element 2) The amount present 3) Humidity 4) Indoor or outdoor exposure. • The effect of heat treatment on the corrosion resistance of magnesium alloys in salt solution.
- 22. FORGING OF ALLOYS • Magnesium alloys are best known for their low density, which results in forgings with very low weight. • The problem in magnesium forging is cracking which results from coarse grain sizes. • This can be overcome by additional extrusion process to give sufficient grain size for forging. High-value automotive wheels are among the most recognizable applications for forged magnesium alloys.
- 23. JOINING OF MAGNESIUM ALLOYS • Shielded-metal arc welding • Gas welding • Electric resistance seam and spot welding • Riveting • Bolting • Adhesive bonding
- 24. ADVANTAGES AND DISADVANTAGES OF MAGNESIUM ALLOYS FOR ENGINEERING DESIGN Advantages: • Good machinability. • Good creep resistance to 120 C. • High thermal conductivity. • Easily gas-shield arc-welded. Disadvantages: • High tendency to galvanic corrosion when contact with dissimilar metals or electrolyte. • Difficult to deform by cold working.
- 26. REFERENCES: • Introduction to Physical Metallurgy 2nd Edition – Sidney H Avner • Materials and Processes in Manufacturing 10th Edition – Paul DeGarmo • http://www.mdpi.com/journal/metals/special_issues/magnesium_technology • http://www.rsc.org/periodic-table/element/12/magnesium • http://www.elementalmatter.info/magnesium-properties.htm • http://www.intlmag.org/magnesiumapps/overview.cfm • http://www.totalmateria.com/Article78.htm • https://www.forging.org/design/47-magnesium-alloys • http://forgingmagazine.com/expert-advice/forging-magnesium-alloys