Which two of the following joining processes are autogeneous?
$$(i)$$ Diffusion welding
$$(ii)$$ Electro slag welding
$$(iii)$$ Tungsten inert gas welding
$$(iv)$$ Friction welding

The major difficulty during welding of aluminium is due to its

In solid-state welding, the contamination layers between the surfaces to be welded are removed by

Within the Heat Affected Zone (HAZ) in a fusion welding process, the work material undergoes