Mariusz Prażmowski

Microstructure and Phase Constitution Near the Interface of Explosively Welded Aluminum/Copper Plates

The microstructure changes and the phase constitution within the layers close to the bonding interface strongly influence the properties of bimetallic strips. In this work, the layers near the interface of explosively welded aluminum and copper plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (TEM) equipped with energy dispersive spectrometry (EDX). The study was focused on the identification of the intermetallic phases, the possible interdiffusion between the copper and the aluminum, and the changes in the dislocation structure of the parent plates. In macro-/mesoscale, the interfaces were outlined by a characteristic sharp transition indicating that there was no mechanical mixing between the welded metals in the solid state. In micro-/nanoscale, the layers adhering to the interface show typical deformed microstructure features, i.e., structure refinement, elongated dislocation cells, slip bands, and microtwins (in copper plate). The internal microstructure of the intermetallic inclusion is composed mostly of dendrites. The electron diffractions and TEM/EDX chemical composition measurements revealed three crystalline equilibrium phases of the γ-Al4Cu9, η-AlCu, and Θ-Al2Cu type (the last one was dominant). However, most of the observed phases of the general CumAln type (also crystalline) do not appear in the equilibrium Al-Cu phase diagram. Inside the intermetallic inclusions, no significant regularity in the phase distribution with respect to the parent sheets was observed. Therefore, it was concluded that the processes occurring in the melt determined their local chemical composition.

Microstructure and interfacial reactions in the bonding zone of explosively welded Zr700 and carbon steel plates

Abstract The microstructure of an explosive cladding joint formed between parallel Zr700 alloy and carbon steel plates was examined with the use of scanning and transmission electron microscopes equipped with energy dispersive spectrometry. The study focused on near-the-interface microstructural changes and possible interdiffusion between the plates. At the macro-scale, the interfaces were outlined by a characteristic sharp transition, indicating that there was no mechanical mixing between the welded metals in the solid state. At the micro-scale, the melted zones often showed non-uniform swirl-like areas of a similar contrast. The nano-scale analysis revealed that the melted areas were composed of mixed amorphous and nano-crystalline phases. The bonding was always achieved by way of surface melting of the joined materials, which might be invisible for observation methods other than transmission electron microscopy.

The Effect of the Detonation Velocity in Explosively Welded Steel-Zirconium Bimetal on the Residual Stresses Determined by the Hole-Drilling Method

As a result of the explosion welding, residual stresses are generated in the cladded material which can affect the properties of the bimetallic composite. This paper analyses the value of residual stresses in the steel-zirconium bimetal sheets, for which the detonation velocities were 1,0V0 (where V0 = 2200m/s); 1,3V0 and 1,6V0 with constant others welding parameters.

Influence of the Microstructure on the Fatigue Cracks Growth in the Joint Zirconium-Steel Made by Explosive Welding

This paper assesses the effect of various values of detonation velocity on the quality of the bond zone. The results of structural, static and fatigue studies were presented for bonds in the initial state. Depending on the applied technological settings of welding, most cases displayed a wavy bond with highly diversified parameters of the wave. High detonation velocities favoured the formation of waves with great height and length and clearly affect the increase in the volume of hard and brittle regions of melt in the bond zone. Increased volume of the melted regions in the bond zone results in the decrease of fatigue resistance and strength properties of the clads.

Orientation changes near the interface of explosively bonded (carbon steel)/Zr700 sheets

The microstructure and texture of explosively welded carbon steel (base) and Zr700 (flyer) plates were characterized by means of scanning electron microscopy equipped with a high resolution electron backscattered diffraction facility. The orientation maps demonstrate that the deformed zones near-the-interface are composed of several layers, the width of which depends on the applied bonding parameters. For both metals, the very thin layer of ultra-fine grains directly adheres to the interface. In the areas more distanced from the interface, the structure evolution depends on the plate material. In the case of a Zr 700 sheet the second layer is formed by highly dislocated (sub)grains, which progressively evolve, towards the structure composed of only lightly deformed grains. In the case of a carbon steel sheet, the second layer near the interface was composed of flattened grains.

Influence of the Microstructure near the Interface on the Fatigue Life of Explosively Welded (Carbon Steel)/Zr Clads

The paper presents joint zone microstructure and the test results obtained for fatigue cracks in zirconium-steel bimetal under bending. The materials were joined with explosive welding technology, and special attention was paid to characteristics of the joint zone.

Experimental Investigation of Texture Gradients in Aluminium/Copper Plates Bonded through Explosive Welding Process

In this study, the commercial purity Al/Cu plates were bonded through the explosive welding process. The SEM/EBSD local orientation measurements were conducted to consider the changes in the microstructure and the development of texture gradients for the applied explosive loading. A particular attention was paid to the texture changes across the interface. The detailed local orientation measurements show that the ultra-fine grained layers are formed close to the bonding zone. The layers were characterized by the copper-type rolling texture components. The interface was outlined by a characteristic sharp transition between the two materials. However, in some places, local melted zones were also encountered, mainly in the front slope of the waves.

Microstructure and Mechanical Properties of Ti/Cu Clads Manufactured by Explosive Bonding at Different Stand-Off Distances

In this study, unalloyed titanium (Gr.1) and deoxidized high phosphorus copper plates were joined through explosive welding process. Different stand-off distances were used to investigate their influence on the microstructure and mechanical properties of the clad fabricated at the same amount of explosive charge. Microstructures near-the-interface were examined with the use of scanning electron microscope equipped with energy dispersive X-ray spectrometer and then microhardness measurements were carried out on the clad. Microstructure examinations showed that with increasing stand-off distance the length and amplitude of the waviness and the quantity of melted zones in areas near-the-interface increase. The inclusions of the melted zones are formed behind the wave crests on titanium side or within the wave vortex. Microhardness measurements indicate a significant increase of both plates microhardness, especially near-the-interface.