Engineering Materials - Study Mode

[#286] When low carbon steel is heated up to upper critical temperature
Correct Answer

(B) The average grain size is a minimum

Explanation

Solution: When low carbon steel is heated up to upper critical temperature, the average grain size is a minimum.

[#287] When low carbon steel is heated up to lower critical temperature
Correct Answer

(A) There is no change in grain size

Explanation

Solution: When low carbon steel is heated up to lower critical temperature There is no change in grain size

[#288] The lower critical temperature
Correct Answer

(C) Is same for all steels

Explanation

Solution: The lower critical temperature is same for all steels. Lower critical temperature for steel’s austenite-to-pearlite transformation is 1333°Fahrenheit (723°Celsius). Below this temperature, austentite doesn’t exist.

[#289] The temperature at which ferromagnetic alpha iron transforms to paramagnetic alpha iron is
Correct Answer

(A) 770°C

Explanation

Solution: Below 773°C (1,423°F), alpha iron becomes ferromagnetic (i.e., capable of being permanently magnetized), indicating a change in electronic structure but no change in crystal structure.

[#290] The unit cells
Correct Answer

(D) All of the above

Explanation

Solution: 1.The unit cells Contain the smallest number of atoms which when taken together have all the properties of the crystals of the particular metal 2. The unit cells Have the same orientation and their similar faces are parallel 3. The unit cells May be defined as the smallest parallelepiped which could be transposed in three coordinate directions to build up the space lattice