PSI - Issue 39

Szymon Derda et al. / Procedia Structural Integrity 39 (2022) 441–449 Author name / Structural Integrity Procedia 00 (2019) 000–000

442

2

1. Introduction As the enhancement of the performance of engineering structures is becoming more challenging, the heterostructured materials [1] could be the solution to satisfy the needs of highly demanding branches of industry [2,3]. When it is crucial to combine high mechanical strength with corrosion resistance or low density there might be no single material to meet these requirements. Joining dissimilar materials, especially of large size, is very challenging. Explosion welding is one of a few appropriate methods that can be used in such situations. It is a solid-state joining process that employs the energy of detonation to accelerate sheets of flyer material toward the base plate. During a high-speed collision, a solid bond can be formed between them [4]. There are some consequences to consider when incorporating explosion welding i.e. severe material deformation, high-temperature gradients, and phase changes that occur and leave a trace in the material in the form of shrinkage cracks, adiabatic shear bands, and residual stress [5– 7]. Tantalum is most widely known for its use in the electronic industry but also a lot of tantalum-based products are implemented in the automobile, medical, and space industries as performance is crucial in these branches of engineering. Moreover, the material finds its use in nuclear reactors, missile parts, chemical processing equipment, heat exchangers, and storage tanks due to its remarkable heat, chemical, and corrosion resistance [8–14]. As the material itself is very limited and expensive, using it as a thin layer of coating appears to be a perfect solution to utilize its unique features. Limited studies on fatigue testing of explosively welded metal composites can be found in the literature. The influence of heat treatment on the fatigue life of three-layer composite has been the subject of [15]. In [16] the same material was inspected in terms of primary crack formation under fatigue loading in the low-cycle regime. It was found that the cracks can form at the interface. Similar observations were reported by Karolczuk [17] regarding Ti Gr.1 – S355N bimetal. In this particular case composites with a flatter interface performed better than those with a wavy interface. In [18] explosively welded steel-based composites cladded with Zr 700 were examined and the research team has concluded that primary cracks can occur at the interface and lead to fatigue failure of the material. Moreover, in some cases cracks that initiated at the interface stoped developing. The interface of explosively welded materials can be a crack initiation site and depending on its morphology, the cracks can develop leading to fatigue failure. These observations show that further analysis of such behavior should be performed to deepen the understanding of disadvantageous features which might influence the fatigue life of such materials The paper presents the results of a study on the fatigue life and failure mechanism of explosively welded metal composites consisting of three layers including steel, copper, and tantalum.

Nomenclature E

Young’s modulus F max Maximum force σ max Maximum stress ε ax Maximum strain A Cross-section area Ta/Cu Interface between tantalum and copper layers Cu/SS Interface between copper and stainless-steel layers (Case 2) Cu/S Interface between copper and steel (Case 1)

2. Materials and methods 2.1. Materials

Two explosively welded metal composites were subjected to fatigue testing. Though the materials consisted of tantalum, copper, and steel there were some important differences between them. The first one, further referred to