Question

In a high-performance jet engine, which of the following materials is best suited for the external engine enclosureIt is subject to small cyclic stress, low mean stress, and atmospheric temperatures. Cost is an issue and shown qualitatively by the dollar signs. O Polycrystalline pure nickel, average grain size ($) O Polycrystalline Ni-20Cr-10Co, average grain size = 100 microns ($$) O Polycrystalline Ni-20Cr-10Co, average grain size = 10 microns ($$$) O Single-crystal Ni-10Cr-8C0-6W-5Ta (

Answer 1

For high-performance jet engine and subjected to small cyclic stress, a material having below the property

1) Good Impact resistance

2) Stability of high operating temperature.

Increase the yield strength by decreasing the grain size because of the amount of pile up at the boundary decrease so that higher applied stress required to move the dislocation.

but in this case, small cyclic stress, low mean stress, and cost as an issue, so use polycrystalline pure nickel, average grain size ($) option A is ans

Polycrystalline pure nickel is a mixture of chromium and stainless steel. following are the properties:

1) Higher-strength and corrosion resistance

2) It is ductile as well as malleable

3) Extent ferromagnet