CWB Level 3
CWB Level 3 Basic Metallurgy and Welding
Metallurgy of Aluminum Exam 2025
What is the cause for weld bead cracking in Al ? - Correct Ans-Hot shortness of Al
What are the properties of Al ? - Correct 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. - Correct Ans-True
Thermal conductivity of Al is _______ times that of Steel - Correct Ans-4
Melting point of Al is about _______ of Steel - Correct Ans-half
Coefficient of thermal expansion for Al is about _______ that of Steel - Correct Ans-
twice
Modulus of elasticity (stiffness) for Al is about _______ that of Steel - Correct Ans-one-
third
True / False
"Nitrogen is not inert to Al and is not used for sheilding" - Correct Ans-True
What is responsible for Al's excellent corrosion resistance? - Correct 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 ? - Correct 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 - Correct Ans-True
True / False ?
The oxide transformation from aluminum oxide to magnesium oxide or magnesium
spinel ,has a profound effect on the solid -state bonding b/w any clad and the Al base -
Correct Ans-True
CWB Level 3
,CWB Level 3
The solid -state bonding b/w Al and another metal or another Aluminum alloy generally
requires a control of the magnesium level to ____ % - Correct Ans-Less than 0.05%
Why does Mg has the profound influence on the oxide found on Al? - Correct Ans-1.
Mg has a greater affinity than Al for O2.
2. Mg behaves as a surface-active element in Al, that is, it tends to diffuse readily to the
surface of the metal.
The oxidation rate of Mg containing alloys is _____________ than for Mg free alloys. -
Correct Ans-greater
Why is oxide thickness on an Mg- Al alloy surface thicker than one on a Mg free alloy
for the same thermal / mechanical history? - Correct Ans-The oxidation rate of Mg
containing alloys is greater than for Mg free alloys.
Which is the element which reacts with Mg oxide to form its oxides on the Al surface? -
Correct Ans-Lithium
Which is the surface oxide for lithium bearing Al alloys? - Correct Ans-Lithium oxide /
spinel
True / False ?
When the Al oxide is transformed to lithium oxide or spinal, then the coherency between
the oxide and the metal substrate may change. Instead of the oxide being tenacious it
may be a porous scale layer that does not protect the parent metal or that can readily
trap moisture or any other air borne contaminant. - Correct Ans-True
True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to minimize the weld
porosity - Correct Ans-True
True / False?
After mechanical milling or chemical treatment for oxide removal prior to welding, the
surface will almost instantly re-oxidize in dry air. - Correct Ans-True
True / False
Oxide removal prior to welding, the surface will form local electrolytic cells between dry
and wet sections and the wet part will corrode preferentially, forming a stain. - Correct
Ans-True
True / False
CWB Level 3
, CWB Level 3
Al loses strength with welding - Correct Ans-True
Fluxes that can dissolve the oxides on Al are ............ - Correct Ans-Halide compounds
( Fluorine, chlorine, Bromine etc.)
Chlorine gas from a Chloride flux in presence of an arc can create poisonous gas called
.......... - Correct Ans-Phosgene (COCL2) or Mustard gas produced by the reaction of
chlorine and carbon monoxide in the presence of intense light
Why are Chlorine fluxes removed completely from the weld region? - Correct Ans-bcz
its hygroscopic. The part will be susceptible for corrosion
What is the drawback of the SMAW welding of Al with Chlorine coated electrodes? -
Correct Ans-1. Cause Lack of Fusion
2. electrodes restricted to Al - Si, Al-Mg-Si and Al- Mg-Si-Cu alloys welding only
3. It cannot be applied to a high magnesium-containing alloy such as AA5083.
At what temp does Al melts? - Correct Ans-660 C
At what temp does Al oxides melts ? - Correct Ans-2072 C
True / False?
Fluxes are not a viable route to remove the oxides on the surface during welding -
Correct Ans-True
The thermal conductivity of Al is ......... times that of steel - Correct Ans-4
True / False?
Among Al alloys ,the thermal conductivity can vary by a factor of two and has a
pronounced effect on the welding parameters. - Correct Ans-True,
Alloying or impurity elements such as titanium , Lithium , magnanese and magnesium
can lower the thermal conductivity
The melting point of the oxides on the Al surface is ....... times greater than the melting
point of the metal - Correct Ans-3
True / False?
For Al, for the same welding energy input, weld penetration varies by the ratio of the
thermal conductivity of 6061 T6 (167 W/mK) to that of AA-5083-O (117W/mK), which is
1.43 - Correct Ans-True
For the same heat input, AA-5083 will have a ................. penetration weld than 6061 T6
- Correct Ans-deeper
CWB Level 3
CWB Level 3 Basic Metallurgy and Welding
Metallurgy of Aluminum Exam 2025
What is the cause for weld bead cracking in Al ? - Correct Ans-Hot shortness of Al
What are the properties of Al ? - Correct 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. - Correct Ans-True
Thermal conductivity of Al is _______ times that of Steel - Correct Ans-4
Melting point of Al is about _______ of Steel - Correct Ans-half
Coefficient of thermal expansion for Al is about _______ that of Steel - Correct Ans-
twice
Modulus of elasticity (stiffness) for Al is about _______ that of Steel - Correct Ans-one-
third
True / False
"Nitrogen is not inert to Al and is not used for sheilding" - Correct Ans-True
What is responsible for Al's excellent corrosion resistance? - Correct 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 ? - Correct 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 - Correct Ans-True
True / False ?
The oxide transformation from aluminum oxide to magnesium oxide or magnesium
spinel ,has a profound effect on the solid -state bonding b/w any clad and the Al base -
Correct Ans-True
CWB Level 3
,CWB Level 3
The solid -state bonding b/w Al and another metal or another Aluminum alloy generally
requires a control of the magnesium level to ____ % - Correct Ans-Less than 0.05%
Why does Mg has the profound influence on the oxide found on Al? - Correct Ans-1.
Mg has a greater affinity than Al for O2.
2. Mg behaves as a surface-active element in Al, that is, it tends to diffuse readily to the
surface of the metal.
The oxidation rate of Mg containing alloys is _____________ than for Mg free alloys. -
Correct Ans-greater
Why is oxide thickness on an Mg- Al alloy surface thicker than one on a Mg free alloy
for the same thermal / mechanical history? - Correct Ans-The oxidation rate of Mg
containing alloys is greater than for Mg free alloys.
Which is the element which reacts with Mg oxide to form its oxides on the Al surface? -
Correct Ans-Lithium
Which is the surface oxide for lithium bearing Al alloys? - Correct Ans-Lithium oxide /
spinel
True / False ?
When the Al oxide is transformed to lithium oxide or spinal, then the coherency between
the oxide and the metal substrate may change. Instead of the oxide being tenacious it
may be a porous scale layer that does not protect the parent metal or that can readily
trap moisture or any other air borne contaminant. - Correct Ans-True
True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to minimize the weld
porosity - Correct Ans-True
True / False?
After mechanical milling or chemical treatment for oxide removal prior to welding, the
surface will almost instantly re-oxidize in dry air. - Correct Ans-True
True / False
Oxide removal prior to welding, the surface will form local electrolytic cells between dry
and wet sections and the wet part will corrode preferentially, forming a stain. - Correct
Ans-True
True / False
CWB Level 3
, CWB Level 3
Al loses strength with welding - Correct Ans-True
Fluxes that can dissolve the oxides on Al are ............ - Correct Ans-Halide compounds
( Fluorine, chlorine, Bromine etc.)
Chlorine gas from a Chloride flux in presence of an arc can create poisonous gas called
.......... - Correct Ans-Phosgene (COCL2) or Mustard gas produced by the reaction of
chlorine and carbon monoxide in the presence of intense light
Why are Chlorine fluxes removed completely from the weld region? - Correct Ans-bcz
its hygroscopic. The part will be susceptible for corrosion
What is the drawback of the SMAW welding of Al with Chlorine coated electrodes? -
Correct Ans-1. Cause Lack of Fusion
2. electrodes restricted to Al - Si, Al-Mg-Si and Al- Mg-Si-Cu alloys welding only
3. It cannot be applied to a high magnesium-containing alloy such as AA5083.
At what temp does Al melts? - Correct Ans-660 C
At what temp does Al oxides melts ? - Correct Ans-2072 C
True / False?
Fluxes are not a viable route to remove the oxides on the surface during welding -
Correct Ans-True
The thermal conductivity of Al is ......... times that of steel - Correct Ans-4
True / False?
Among Al alloys ,the thermal conductivity can vary by a factor of two and has a
pronounced effect on the welding parameters. - Correct Ans-True,
Alloying or impurity elements such as titanium , Lithium , magnanese and magnesium
can lower the thermal conductivity
The melting point of the oxides on the Al surface is ....... times greater than the melting
point of the metal - Correct Ans-3
True / False?
For Al, for the same welding energy input, weld penetration varies by the ratio of the
thermal conductivity of 6061 T6 (167 W/mK) to that of AA-5083-O (117W/mK), which is
1.43 - Correct Ans-True
For the same heat input, AA-5083 will have a ................. penetration weld than 6061 T6
- Correct Ans-deeper
CWB Level 3
