With which metals are delta fires likely to occur?

Delta fires are associated with metals that can ignite and burn rapidly when they are in fine particle form or when exposed to high temperatures and certain reactive environments. Magnesium and titanium are particularly known for their propensity to ignite when subjected to such conditions.

Magnesium, for instance, can easily catch fire and burns with a bright white flame, producing intense heat. This property makes it highly reactive, especially if it is powdered or in thin strips. Titanium, while more stable than magnesium, can also burn when it is finely divided or when heated to elevated temperatures, which may occur in several industrial applications.

In contrast, while aluminum and copper can also be problematic in certain circumstances, they do not share the same level of risk for delta fires as magnesium and titanium. Iron and brass, as well as lead and zinc, also do not have the same fire hazards associated with them under typical conditions. Their reactivity under fire conditions does not lead to the type of intense and uncontrollable fires associated with magnesium and titanium.

Thus, the correct choice reflects the unique fire hazards presented by magnesium and titanium, making them the most likely candidates for delta fires among the options given.