Which material is known to become brittle at temperatures exceeding 800F?

• A. Steel
• B. Titanium
• C. Titanium alloys
• D. Magnesium

Answer: (C)

Titanium alloys are known to exhibit brittleness when exposed to high temperatures, particularly those exceeding 800°F. At these temperatures, the microstructure of titanium alloys can change, leading to a loss of ductility and an increase in brittleness. This phenomenon occurs due to the formation of various detrimental phases and the alteration of the alloy's properties, making it less capable of absorbing energy or deforming without breaking.

While other materials like steel and magnesium also have specific temperature ranges where they can lose their desirable mechanical properties, titanium alloys are particularly sensitive to high temperatures in this regard. Steel can maintain its structural integrity to a certain extent and may even gain some strength at elevated temperatures. Magnesium, although it can also be affected by heat, does not undergo brittleness at the same temperature range as titanium alloys. Therefore, the correct identification of titanium alloys as the material that becomes brittle at temperatures exceeding 800°F is supported by the understanding of material behavior and properties at elevated temperatures.