quiz7fall01 - "~ '66 ENSC 3313, Fal12001 Answer anv 1...

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'66 " ~ ENSC 3313, Fal12001 Quiz 7 Name Answer anv 4 Questions onlv. 1 point each This is a cast iron microstructure ofpearlite and cementite. To what w/o C does this correspond? 1 100% Pearlite at 0.8% C, 100% Cementite at 6.7% C I estimate -2/3 pearlite, -1/3 cementite Thus, I am -1/3 of the way from 0.8 to 6.7% C. 0.8 + (6.7 -0.8)/3- 2.8 w/o C 2. A 1080 steel is soaked in the austenite region, thence quenched to 700°C and held for 2s, thence quenched to 300°C and held for 10s, thence quenched to o°C and held for 10 hours. What phases, in what proportions are presented at the mQ of this sequence? We begin with austenite. After 2s at 700°C, there is no transfonnation. O . f- = ... f 8. ~ roo o i- ~ s ~ After 10s at 300°C, transformation. there IS no At 0°C, about 80% of the austenite has converted to martensite, hence we have . .:. 80% martensite, -20% retained austenite. A thin sheet of an eutectoid steel with a coarse pearlite microstructure was heated to 700°C and held there for 10 minutes. It was then guenched to 500°C and held for 3 seconds only before guenching to
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quiz7fall01 - "~ '66 ENSC 3313, Fal12001 Answer anv 1...

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