应力-应变曲线中第二个阶段是？ A: hardening stage B: yielding stage C: elastic stage D: strain hardening stage

The precipitation hardening processes include （） heat treatment and （） heat treatment.

智慧职教: ______ cannot be hardened by heat treatment since they contain no hardening element.

Boron is added to structural steel to increase its ( ). A: tempering stability B: toughness C: hardenability D: hardening capacity

The problems that ferritic steel produces during welding are ( ) and ( ). A: Grain refinement B: Intergranular corrosion C: Toughness increase D: Hardening tendency

The problems that ferritic steel produces during welding are ( ). A: Grain refinement B: Intergranular corrosion C: Toughness increase D: Hardening tendency

In which heat treatment process, the specimen should be cooled in water or oil A: Tempering B: Annealing C: Quenching D: Case hardening

If the heating temperature is increased after recrystallization, ( ) will take place. A: secondary recrystallization B: fine grain strengthening C: work hardening D: solid solution strengthening

I end up getting my heart ______ . For so many years, I was never expressive with my feelings. A: hardened B: hardening C: hardens D: being hardened

What can cause pulse pressure to increase? A: increased peripheral resistance B: increased heart rate C: hardening of the walls of the arterie D: Increased function of the elastic reservoir of the aorta