2. (a) Explain why steel is ductile at room temperature, but may be brittle at a low temperature. (b) A number of treatments can affect the yield strength of the steel, e. g., work hardening, tempering (modifying the precipitates), grain growth (changing the grain size), etc. To minimize the brittle-to-ductile transition temperature (TBD), should we try to increase or decrease the yield strength