A welder is attempting to fusion weld two pieces of 5083 aluminum alloy without filler metal, but frequently encounters hot cracking in the weld bead. What is the most likely metallurgical reason for this issue with 5083, and what solution should be considered?

Question: A welder is attempting to fusion weld two pieces of 5083 aluminum alloy without filler metal, but frequently encounters hot cracking in the weld bead. What is the most likely metallurgical reason for this issue with 5083, and what solution should be considered?

Answer options:

• High thermal expansion coefficient; use a pulsed GMAW process. ✅ Wide freezing range, promoting liquation cracking; use a compatible filler metal.
• Presence of zinc in the alloy, causing porosity; meticulously clean the joint.
• Formation of brittle intermetallic compounds; increase welding speed.

Correct answer: Wide freezing range, promoting liquation cracking; use a compatible filler metal.

Explanation: 5083 aluminum alloy, like many other non-heat-treatable aluminum alloys, has a relatively wide freezing range, which makes it susceptible to hot cracking (also known as solidification cracking or liquation cracking) when fusion welded without a suitable filler metal. Introducing a compatible filler metal, such as ER5356, can modify the weld metal chemistry to produce a fine, non-interconnecting liquid film during solidification, preventing cracking.