Occurrence of microstructures on steel surface under the influence of plasma focus discharge

The surface of metals after irradiation by intense streams of argon plasma arising in the plasma focus was studied. Metal samples of steel, copper, tungsten and molybdenum were investigated. Different types of microstructures were recorded. The surfaces of steel samples contain micropores with sizes of 0.1–3 $\mu$m with a shape close to circular. On copper and tungsten plates the appearance of fine-dispersed structures with sizes of 0.5–20 $\mu$m is observed. The possible mechanisms of the appearance of these microstructures are discussed.