Engineering Materials
In a hardening process, the hypo-eutectoid steel is

Heated from 30°C to 50°C above the upper critical temperature and then cooled slowly in the furnace
Heated from 30°C to 50°C above the upper critical temperature and then cooled in still air
Heated below or closes to the lower critical temperature and then cooled slowly
Heated from 30°C to 50°C above the upper critical temperature and then cooled suddenly in a suitable cooling medium

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Engineering Materials
Dow metal contains

92.5% aluminium and, 4% copper, 2% nickel and 1.5% Mg
94% aluminium, 4% copper and 0.5% Mn, Mg, Si and Fe
90% aluminium and 90% copper
90% magnesium and 9% aluminium with some copper

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Engineering Materials
Duralumin 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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