Which property is characteristic of aluminum alloys in welding?

• A. Low thermal expansion
• B. Very high melting point
• C. High electrical resistance
• D. Higher thermal expansion and high solidification shrinkage

Answer: (D)

Aluminum alloys behave in welding mainly through how they respond to heat and how the weld metal changes as it cools. When aluminum heats up, it expands noticeably—more than many other metals—so the welded area tends to expand during welding. As the weld pool solidifies and then cools, it shrinks a lot, leading to solidification shrinkage. That combination—greater expansion with heat and significant shrinkage on solidification—creates distortion and potential defects if the welding process isn’t carefully controlled.

This is why the property described as higher thermal expansion and high solidification shrinkage is the best fit for aluminum alloys in welding. Other options don’t match aluminum’s behavior: it doesn’t have a very low or very high melting point (it melts around 660°C, relatively low), and while it conducts electricity well, it does not have high electrical resistance.