CWB Level 3 Module 24 Basic Metallurgy and Welding Metallurgy of Aluminum

What is the cause for weld bead cracking in Al ? - ANS ------Hot shortness of Al What are the properties of Al ? - ANS ------1. low density 2. Corrosion resistance 3. High electrical resistance 4. High thermal conductivity 5. good appearance 6. toughness at low temps True / False ? Al is covered with a coherent oxide. - ANS ------True Thermal conductivity of Al is _______ times that of Steel - ANS ------4 Melting point of Al is about _______ of Steel - ANS ------half Coefficient of thermal expansion for Al is about _______ that of Steel - ANS ------twice Modulus of elasticity (stiffness) for Al is about _______ that of Steel - ANS ------one-third True / False "Nitrogen is not inert to Al and is not used for sheilding" - ANS ------True What is responsible for Al's excellent corrosion resistance? - ANS ------Al oxide but it changes to Magnesium oxide (MgO) or Magnesium spinel ( Mg Al2O4) when the Mg % exceeds 0.05%. What is the thickness of Al oxide on the surface of Al ? - ANS ------50-150 angstroms True/ False ? The form of magnesium oxide is a function of the magnesium concentration and the thermal history of the alloy - ANS ------True