Q1: A hot short metal is

ANS:C - brittle when hot.

A hot short metal is brittle when hot. Explanation:

1. Hot Shortness: Hot shortness, also known as hot short, refers to the tendency of certain metals to become brittle and crack when subjected to mechanical stress at elevated temperatures.
2. Behavior of Hot Short Metals: Hot short metals exhibit ductility and toughness at room temperature or when cold but become brittle and lose their mechanical properties when heated to elevated temperatures. This brittleness makes them susceptible to cracking and failure under mechanical loads at high temperatures.
3. Characteristics of Hot Short Metals:
   • These metals are typically ductile and can be formed or worked at room temperature.
   • However, when heated to temperatures near or above their recrystallization or melting points, they lose their ductility and become brittle.
   • Hot short metals may exhibit grain boundary embrittlement or other metallurgical phenomena that cause them to fail catastrophically when subjected to stress at elevated temperatures.
4. Examples of Hot Short Metals: Some examples of metals prone to hot shortness include certain types of low-carbon steels, wrought iron, and some copper alloys.
5. Comparison with Cold Shortness: Hot shortness should not be confused with cold shortness, which refers to brittleness exhibited by certain metals at low temperatures. Cold short metals become brittle and fracture easily when subjected to stress at cold temperatures but may exhibit ductile behavior at higher temperatures.