CWB Level 3 Module 24 Basic Metallurgy and Welding
Metallurgy of Aluminum Practice questions With Answers
What is the cause for weld bead cracking in Al ? - (ANSWERS)Hot shortness of!@#$%%%%%
Al
%%%%%%
What are the properties of Al ? - (ANSWERS)1. Low density
2. Corrosion resistance
3. High electrical resistance
4. High thermal conductivity
5. Good appearance
6. Toughness at low temps
True / False ?
Al is covered with a coherent oxide. - (ANSWERS)True
Thermal conductivity of Al is _______ times that of Steel - (ANSWERS)4
Melting point of Al is about _______ of Steel - (ANSWERS)half
Coefficient of thermal expansion for Al is about _______ that of Steel - (ANSWERS)twice
Modulus of elasticity (stiffness) for Al is about _______ that of Steel - (ANSWERS)one-third
True / False
"Nitrogen is not inert to Al and is not used for sheilding" - (ANSWERS)True
What is responsible for Al's excellent corrosion resistance? - (ANSWERS)Al oxide but it changes
to Magnesium oxide (mgo) or Magnesium spinel ( Mg Al2O4) when the Mg % exceeds 0.05%.
What is the thickness of Al oxide on the surface of Al ? - (ANSWERS)50-150 angstroms
True/ False ?
The form of magnesium oxide is a function of the magnesium concentration and the thermal
history of the alloy - (ANSWERS)True
True / False ?
The oxide transformation from aluminum oxide to magnesium oxide or magnesium spinel ,has
a profound effect on the solid -state bonding b/w any clad and the Al base - (ANSWERS)True
The solid -state bonding b/w Al and another metal or another Aluminum alloy generally requires
a control of the magnesium level to ____ % - (ANSWERS)Less than 0.05%
Why does Mg has the profound influence on the oxide found on Al? - (ANSWERS)1. Mg has a
greater affinity than Al for O2.
,CWB Level 3 Module 24 Basic Metallurgy and Welding
Metallurgy of Aluminum Practice questions With Answers
2. Mg behaves as a surface-active element in Al, that is, it tends to diffuse readily to the surface
!@#$%%%%%
of the metal. %%%%%%
The oxidation rate of Mg containing alloys is _____________ than for Mg free alloys. -
(ANSWERS)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? - (ANSWERS)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? -
(ANSWERS)Lithium
Which is the surface oxide for lithium bearing Al alloys? - (ANSWERS)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. - (ANSWERS)True
True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to minimize the weld porosity -
(ANSWERS)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. - (ANSWERS)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. - (ANSWERS)True
True / False
Al loses strength with welding - (ANSWERS)True
, CWB Level 3 Module 24 Basic Metallurgy and Welding
Metallurgy of Aluminum Practice questions With Answers
Fluxes that can dissolve the oxides on Al are ............ - (ANSWERS)Halide compounds (
!@#$%%%%%
Fluorine, chlorine, Bromine etc.) %%%%%%
Chlorine gas from a Chloride flux in presence of an arc can create poisonous gas called ..........
- (ANSWERS)Phosgene (COCL2) or Mustard gas produced by the reaction of chlorine and
carbon monoxide in the presence of intense light
Why are Chlorine fluxes removed completely from the weld region? - (ANSWERS)bcz its
hygroscopic. The part will be susceptible for corrosion
What is the drawback of the SMAW welding of Al with Chlorine coated electrodes? -
(ANSWERS)1. Cause Lack of Fusion
2. Electrodes restricted to Al - Si, Al-Mg-Si and Al- Mg-Si-Cu alloys welding only
3. It cannot be applied to a high magnesium-containing alloy such as AA5083.
At what temp does Al melts? - (ANSWERS)660 C
At what temp does Al oxides melts ? - (ANSWERS)2072 C
True / False?
Fluxes are not a viable route to remove the oxides on the surface during welding -
(ANSWERS)True
The thermal conductivity of Al is ......... Times that of steel - (ANSWERS)4
True / False?
Among Al alloys ,the thermal conductivity can vary by a factor of two and has a pronounced
effect on the welding parameters. - (ANSWERS)True,
Alloying or impurity elements such as titanium , Lithium , magnanese and magnesium can
lower the thermal conductivity
The melting point of the oxides on the Al surface is ....... Times greater than the melting point of
the metal - (ANSWERS)3
True / False?
For Al, for the same welding energy input, weld penetration varies by the ratio of the thermal
conductivity of 6061 T6 (167 W/mk) to that of AA-5083-O (117W/mk), which is 1.43 -
(ANSWERS)True
Metallurgy of Aluminum Practice questions With Answers
What is the cause for weld bead cracking in Al ? - (ANSWERS)Hot shortness of!@#$%%%%%
Al
%%%%%%
What are the properties of Al ? - (ANSWERS)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. - (ANSWERS)True
Thermal conductivity of Al is _______ times that of Steel - (ANSWERS)4
Melting point of Al is about _______ of Steel - (ANSWERS)half
Coefficient of thermal expansion for Al is about _______ that of Steel - (ANSWERS)twice
Modulus of elasticity (stiffness) for Al is about _______ that of Steel - (ANSWERS)one-third
True / False
"Nitrogen is not inert to Al and is not used for sheilding" - (ANSWERS)True
What is responsible for Al's excellent corrosion resistance? - (ANSWERS)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 ? - (ANSWERS)50-150 angstroms
True/ False ?
The form of magnesium oxide is a function of the magnesium concentration and the thermal
history of the alloy - (ANSWERS)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 - (ANSWERS)True
The solid -state bonding b/w Al and another metal or another Aluminum alloy generally requires
a control of the magnesium level to ____ % - (ANSWERS)Less than 0.05%
Why does Mg has the profound influence on the oxide found on Al? - (ANSWERS)1. Mg has a
greater affinity than Al for O2.
,CWB Level 3 Module 24 Basic Metallurgy and Welding
Metallurgy of Aluminum Practice questions With Answers
2. Mg behaves as a surface-active element in Al, that is, it tends to diffuse readily to the surface
!@#$%%%%%
of the metal. %%%%%%
The oxidation rate of Mg containing alloys is _____________ than for Mg free alloys. -
(ANSWERS)greater
Why is oxide thickness on an Mg- Al alloy surface thicker than one on a Mg free alloy for the
same thermal / mechanical history? - (ANSWERS)The oxidation rate of Mg containing alloys is
greater than for Mg free alloys.
Which is the element which reacts with Mg oxide to form its oxides on the Al surface? -
(ANSWERS)Lithium
Which is the surface oxide for lithium bearing Al alloys? - (ANSWERS)Lithium oxide / spinel
True / False ?
When the Al oxide is transformed to lithium oxide or spinal, then the coherency between the
oxide and the metal substrate may change. Instead of the oxide being tenacious it may be a
porous scale layer that does not protect the parent metal or that can readily trap moisture or
any other air borne contaminant. - (ANSWERS)True
True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to minimize the weld porosity -
(ANSWERS)True
True / False?
After mechanical milling or chemical treatment for oxide removal prior to welding, the surface
will almost instantly re-oxidize in dry air. - (ANSWERS)True
True / False
Oxide removal prior to welding, the surface will form local electrolytic cells between dry and
wet sections and the wet part will corrode preferentially, forming a stain. - (ANSWERS)True
True / False
Al loses strength with welding - (ANSWERS)True
, CWB Level 3 Module 24 Basic Metallurgy and Welding
Metallurgy of Aluminum Practice questions With Answers
Fluxes that can dissolve the oxides on Al are ............ - (ANSWERS)Halide compounds (
!@#$%%%%%
Fluorine, chlorine, Bromine etc.) %%%%%%
Chlorine gas from a Chloride flux in presence of an arc can create poisonous gas called ..........
- (ANSWERS)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? - (ANSWERS)bcz its
hygroscopic. The part will be susceptible for corrosion
What is the drawback of the SMAW welding of Al with Chlorine coated electrodes? -
(ANSWERS)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? - (ANSWERS)660 C
At what temp does Al oxides melts ? - (ANSWERS)2072 C
True / False?
Fluxes are not a viable route to remove the oxides on the surface during welding -
(ANSWERS)True
The thermal conductivity of Al is ......... Times that of steel - (ANSWERS)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. - (ANSWERS)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 - (ANSWERS)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 -
(ANSWERS)True
