Journal of Welding Science

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The conventional eddy current method for non-destructive inspection of welding joints has limitations that can examine defects to a certain depth below the surface of the sample and is not suitable for determining deep defects. This limitation can be overcome using the SQUID superconducting sensors. The nonstoichiometric composition of YBCO due to its superconducting temperature and desired critical current density is widely used including the use of highly sensitive SQUID sensors. The properties and temperature of the superconducting compound are related to producing pure and homogeneous with a precise ratio of this non-stoichiometric compound in phase Y:123. In this study, the production of this high-temperature superconductor was carried out using a sol gel self-combustion process with nitrate forming elements and then produced powder analyzed by TGA, XRD, scanning electron microscopy, and EDX method and optimum conditions for production of Y:123 superconducting nanopowder were obtained by sol gel self-combustion method. In these conditions, the superconducting phase Y:123 was produced and the impurities were removed and on the other hand, the need for further thermal treatment and the costly annealing process were removed. Finally, optimal conditions for deposition of this compound on the substrate for producing the SQUID sensor were investigated and an optimal condition was presented to produce thin layer YBCO deposited by pulsed laser deposition method and patterned to produce SQUID High temperature Superconductor SQUID sensor. Finally the SQUID based NDT test for detecting sub-surfaces defects was investigated.

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This research focuses on the dissimilar joining of Ti6Al4V and Inconel 718 alloys using the Transient Liquid Phase (TLP) bonding process with a BNi2 foil and a copper interlayer. The objective is to analyze the effects of temperature (850, 950, and 1050 °C) and holding time (10, 20, and 30 minutes) on the microstructure, phase composition, and mechanical properties of the bonding region. DSC analysis indicated that melting reactions begin around 950 °C, attributed to the formation of eutectic compounds in the Cu-Ni-B system. SEM and EDS examinations confirmed the formation of intermetallic phases such as Ti₂Ni, NiTi, Cr₂Ti, and ceramic phase Ni₃B in different regions of the joint. Under optimal conditions (950 °C for 20 minutes), a uniform microstructure, controlled boron diffusion, and formation of stable phases were observed. The hardness in the DAZ region was approximately 420–450 HV. In contrast, higher temperatures and extended holding times led to the formation of brittle phases, solidification cracks, and interfacial discontinuities. The diffusion coefficient of titanium under optimal bonding conditions was estimated to be 2.8×10⁻¹¹ m²/s. These findings emphasize the importance of precise control over process parameters to achieve high-quality joints and prevent structural defects.