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Unformatted text preview: 7. A turbine blade is to be manufactured in the form of a single crystal that is grown simply by freezing the part from one end to the other as shown in the accompanying diagram. The alloy is 67 wt% Ni, the solid line on the phase diagram (although a turbine blade would never be this particular alloy!). The dashed line on the curve shows the average composition of the solidified part during freezing (diffusion is slow in this solid!). (a) The single crystal blade was service-tested at temperature T = 1250 C and catastrophic fracture occurred. What happened? (b) An engineer suggested that blades could be annealed (heat treating) at T = 1200 C prior to use at 1250 C. Is this suggestion sound in principle? (c) If the diffusivity at 1200 C is 10-9 cm 2 /sec and the blade is 10 cm long, how long would the blade have to be annealed to solve the problem? Is annealing at 1200 C a practical solution to this problem?...
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This note was uploaded on 11/21/2011 for the course MAT SCI 201 taught by Professor Matsci during the Spring '10 term at Northwestern.
- Spring '10