Engineering Materials
When low carbon steel is heated up to lower critical temperature

The grain size first increases and then decreases very rapidly
The grain size increases very rapidly
The average grain size is a minimum
There is no change in grain size

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Engineering Materials
Duralumin contains

5 to 6% tin, 2 to 3% copper 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
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

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