Solid Solution Hardening Phase
A homogeneous interstitial or substitutional phase where foreign atoms elastically strain the crystal lattice and hinder dislocation motion.
Solid solution strengthening occurs when foreign atoms dissolve in the lattice of the base material. The atoms strain the lattice and impede the movement of dislocations – the material becomes harder and stronger. When welding, you have to watch out: the heat input and cooling rate determine how much of these elements go into solution. Too much makes the weld metal brittle and prone to cracking, too little and you don't get the desired strength. So make sure that the composition of your filler metal matches the base material. If you're unsure how the material will react, check the data sheet or ask the supplier.