M. Atashparva, M. Hamedi,
Volume 3, Issue 2 (1-2018)
Abstract
Nowadays, due to the need for miniaturization, small scale resistance spot welding is of interest. The key factor that determines the nugget size is contact resistance. In this paper a new equation is provided to calculate the electrical contact resistance. The model can predict the high temperature contours and the nugget configuration efficiently. Also, a set-up was constructed to verify the model and investigate the effects of parameters on the mechanical properties of Hastelloy X welded joints. DOE analysis is done to recognize the effect of parameters on the nugget diameter, maximum load, and nugget height. It was concluded that the size of the nugget enlarges by increasing welding current and time. The nugget diameter decreases with increase of force.
Mr E. Ganjeh, Dr Ali Kaflou, Dr Kourosh Shirvani,
Volume 9, Issue 2 (1-2024)
Abstract
In this study, mechanical properties of the transient liquid phase (TLP) bonds between Hastelloy X to Ni3Al IMC at temperature range of 800 - 900 °C were investigated. The microstructure of the joints was examined by optical and scanning electron microscopy. Also, high temperature XRD (HTXRD) analysis was utilized to investigate the phase changes at different temperatures of half-joints. According to microscopic observations, the joint cross-section consisted of three regions including diffusion affected zone (DAZ), isothermal solidification zone (ISZ), and Athermal solidification zone (ASZ), which increasing temperature and time result in ISZ consisting of nickel-rich solid solution developed across the microstructure. The optimum joint bonding strength was achieved for the sample treated at 1100 °C – 180 min equal to 355 ± 4.5 MPa. The ultimate tensile strength reached 36.5 ± 1 and 20.5 ± 1 MPa at temperatures of 800 °C and 900 °C, respectively. Fracture occurred on the side of the IMC substrates at both test temperatures due to the presence of shrinkage porosity during the solidification stage of IMC and crystal lattice parameters mismatch with the matrix.
