What does the term 'supercooling' refer to in the context of pulse-spray transfer mode?

In the context of pulse-spray transfer mode within Gas Metal Arc Welding (GMAW), the term 'supercooling' specifically refers to the process of cooling the weld pool during the background cycles of the pulsing waveform. The pulse-spray transfer mode operates by rapidly alternating between high and low current settings. When the current is reduced during the background cycle, the temperature of the weld pool decreases significantly, which creates an environment where the molten metal solidifies at a faster rate than it would under continuous current conditions. This rapid cooling helps to refine the microstructure of the weld, improve mechanical properties, and enhance the control over the weld bead shape and size.

It's essential to note that while other options reference processes related to temperature and heat in welding, they do not accurately describe the specific phenomenon of 'supercooling' as it is understood in pulse-spray transfer mode.