FEATURES OF METALLOGRAPHY OF THE WELDED JOINT OF AMg6 + AMg6 ALUMINUM PLATES AFTER EXPLOSION WELDING
In this work, the selection of the method of sample preparation and the choice of the etchant for obtaining high-contrast images of the microstructure of aluminum and welded joints of aluminum and its alloys obtained by explosion welding is carried out. The prepared microsections were initially etched by immersion in Keller's reagent (95 ml of water, 2,5 ml of nitric acid, 1,5 ml of hydrochloric acid, 1 ml of hydrofluoric acid) for 15-20 s. Then the samples were washed with water and dried. With this etching, the overall microstructure is etched satisfactorily. However, not all grain boundaries are etched in contrast and, in addition, the nature of the inclusions is not entirely clear. Longer exposures in Keller's reagent lead to the appearance of etching artifacts in the form of etching pits and over etching of individual phase components, which complicates their further identification. To visualize the nature of inclusions and more contrasting etching, samples already etched in Keller's reagent were etched in Weck's reagent (100 ml of water, 4 g of potassium permanganate, and 1 g of sodium hydroxide) by immersing the sample for a 20 s, after which the samples were washed with water and dried. Sequential etching of aluminum alloys allows more contrast and visualization of the microstructure features. Keller's reagent is recommended as the main etching reagent, and Wek's reagent as an additional one, which additionally colors some structural components.