What is the hardness (HB) of each of the alloys? (a) 0.25 wt%C with spheroid:te,
(b) 0.25 wt%C with coarse pearlite,
(c) 0.60 wt%C with fine pearlite, and
(d) 0.60 wt%C with coarse pearlite.

A) 62.5 HB

B) 75 HB

C) 95 HB

D) 90 HB

Explanation:

From the attached animated figure, we can trace the values of hardness (HB) for each of the alloys.

The scale we are using in the attachment to read our values for HB is the HRB scale that shows the Rockwell hardness on the right hand side.

A) For 0.25 wt%C with spheroidite, Tracing the line out on the green curve and reading the scale on the right, the hardness is approximately 62.5 HB

B) For 0.25 wt%C with coarse pearlite, Tracing the line out on the blue curve and reading the scale on the right hand side, the hardness is approximately 75 HB

C) For 0.60 wt%C with fine pearlite, Tracing the line out on the red curve and reading the scale on the right hand side, the hardness is approximately 95 HB

D) For 0.60 wt%C with coarse pearlite. Tracing the line out on the blue curve and reading the scale on the right hand side, the hardness is approximately 90 HB

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the answer is d.) potassium