Engineering Materials
Chromium in steel

Refines grain size and produces less tendency to carburisation, improves corrosion and heat resistant properties
Gives ductility, toughness, tensile strength and anti-corrosion properties
Improves wear resistance, cutting ability and toughness
Improves cutting ability and reduces hardenability

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Engineering Materials
Points of arrest for iron correspond to

There is nothing like points of arrest
Stages at which further heating does not increase temperature for some time
Stages at which allotropic forms change
Stages at which properties do not change with increase in temperature

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Engineering Materials
Which of the following statement is true about brittle fracture?

High temperature and low strain rates favour brittle fracture
Brittle fracture is always preceded by noise
Many metals with hexagonal close packed (H.C.P) crystal structure commonly show brittle fracture
Cup and cone formation is characteristic for brittle materials

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Engineering Materials
Y-alloy contains

5 to 6% tin, 2 to 3% copper and rest aluminium
3.5 to 4.5% copper, 1.2 to 1.7% manganese, 1.8 to 2.3% nickel, 0.6% each of silicon, magnesium and iron, and rest aluminium
4 to 4.5% magnesium, 3 to 4% copper and rest aluminium
3.5 to 4.5% copper, 0.4 to 0.7% magnesium, 0.4 to 0.7% manganese and rest aluminium

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