Investigation of the Nature of the Fracture of the Joint Zone in Samples of Aluminum-Copper Bimetal Obtained by Explosion Welding Near the Lower Limit of Weldability

The paper presents the results of quantitative fractography of the copper-aluminum bimetal junction using scanning electron microscopy. The component content in the fracture of the samples after mechanical testing was calculated as the ratio of the area of the visible contrast areas to the total area of the electronic image. It was found that when an equal-strength welded joint is formed between copper and aluminum near the lower limit of weldability (W2 from 0.17 to 0.24 MJ/m2), the melt content in the fracture decreases from 55-63 % to 27-21 % with a constant linear melt content of 56-67 %. At the same time, the number of aluminum regions increases from 34-36 % to 57-73 %, which indicates a shift in the fracture zone from the melts deeper into the aluminum with a change in the predominant fracture pattern from brittle to viscous.