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2 2024

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How to suppress the Kirkendall porosity within the Ti/Ni explosive welds?

Wojewoda-Budka Joanna, Kwiecien Izabella, Bigos Agnieszka, Terlicka Sylwia, Litynska-Dobrzynska Lidia, Petrzak Paweł, Wierzbicka-Miernik Anna, Szczerba Maciej, Szulc Zygmunt, Rabkin Eugen

Archives of Civil and Mechanical Engineering

2024

Vol. 24, no. 2

art. no. e117, 2024

Pure Ti (Grade 1) and Ni (type Ni201) were used to produce the Ti/Ni welds employing the explosive welding process. Thermal expansion of the welded plates was determined using dilatometric measurements from room temperature up to 600 °C. The results showed that the thermal expansion coefficient of Ti/Ni welded plates is closer to that of pure nickel than would be suggested by the Timoshenko’s model for bimetallic strip. The microstructure of the Ti/Ni interface after exposure to high temperatures revealed the presence of extensive interface porosity (Kirkendall porosity). This may cause a catastrophic disintegration of the weld during working or essential forming. The welded plates were annealed at the temperature of 650 °C under different applied compressive loads, and the applied load was shown to alter the microstructure of the Nix<.sub>Tiy phases present at the Ti/Ni interface. Based on the obtained interface microstructural data, the strategy to suppress the Kirkendall porosity at the interface was proposed.

Compression behavior of cast high‑porosity magnesium with directionally oriented structure

Janus Karol, Liu Yuan, Drenchev Ludmil, Burbelko Andriy, Ostachowski Paweł, Darłak Paweł, Piekło Jarosław, Sobczak Natalia, Krastev Rumen, Simeonova Tatiana, Tarasiuk Jacek, Wroński Sebastian, Terlicka Sylwia, Sobczak Jerzy Józef

Archives of Civil and Mechanical Engineering

2024

Vol. 24, no. 2

art. no. e55, 2024

The influence of different porosity levels of magnesium gasars manufactured with the use of the Bridgman-type directional solidification method on their compression behavior was investigated. The cross-section structure perpendicular to the height of the produced gasars ingots was characterized using X-ray computed tomography (CT). These results indicated that gasars with porosities of 30%, 36%, 39%, and 48% were obtained, and those with porosities of 30% and 36% had a homogenous porosity distribution and the uniform diameter of the pores. Compression tests were carried out to compare the mechanical properties of the manufactured gasars vs cast porosity-free magnesium. The gasar with 30% porosity achieved the highest compressive strength (Rc) of all the tested gasars ingots, which was 107 MPa. In addition, when the compressive strength was calculated for the sample cross-section, excluding its porosity, the modified compressive strength (MRc) of 152 MPa was obtained for the gasar with 30% porosity, and it was about 8.5% higher than the compressive strength of monolithic porosity-free magnesium. Moreover, taking into account the density of tested material, the gasar with 30% porosity achieved the highest specific strength and the highest energy absorption capacity among all the tested magnesium gasars. For the examined materials, numerical simulations of the compression behavior were performed, and the results obtained are discussed in terms of the mechanism controlling the strengthening process in a high-porosity magnesium with directional oriented structure.