Definitions for "Heat Affected Zone"
That portion of the base metal that has not been melted but whose microstructure or mechanical properties have been altered by the heat of welding, brazing, soldering, forming, or cutting.
the immediate region around a thermal machining process (laser ablation, electrical discharge machining, etc) where the mechanical properties of the work material are changed by rapid cooling (quenching), usually makes work material locally more brittle
Heat affected zone is the region close to the laser irradiated area that obvious temperature change from original area happens, or obvious strain state change happens.