Engineering Materials
Addition of copper to aluminium results in

One of the best known age and precipitation hardening systems
Improvement of corrosion resistance
Improvement of casting characteristics
Improving machinability

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Engineering Materials
Points of arrest for iron correspond to

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

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

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 in still air
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 suddenly in a suitable cooling medium

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