Showing 4 results for Naffakh-Moosavy
A. Hajitabar, H. Naffakh-Moosavy,
Volume 4, Issue 2 (Journal OF Welding Science and Technology of Iran 2019)
Abstract
The effect of electron beam welding current changes on the microstructure and mechanical properties of the Nb-based alloy has been investigated. The electron beam welding was applied with 4 different currents of 20, 24, 30 and 35 mA on 3mm thick plates. The aspects including different welding regions, geometry and depth of welding penetration, as well as the effect of heat input on the weldability are investigated. The mechanical properties including tensile and microhardness values of the weld was also measured. The results show that in a sample with a 30 mA welding current, the optimum conditions for the depth of penetration, weldability and the geometry of the weld are obtained. The welds showed a cellular structure, and intercellular dendrites in the central region of the weld have been caused due to microsegregations created between the cells. In HAZ, severe recrystallization and grain growth has occurred. Because of the high thermal conductivity of niobium, the HAZ size is relatively large. Based on the 3D Rosenthal’s equation, the recrystallization temperature of alloy was calculated as 713 °C. It is observed that as G × R increases, the grain size in the central line of the weld decreases. The hardness profile shows that the hardness of the weld zone and the HAZ is significantly less than that of the base metal due to elimination of work hardening effect. The tensile strength of the weld for a sample with a current of 30 mA was 281MPa, which is 53% of the tensile strength of the base metal and the weld was broken from the HAZ.
Dr Homam Naffakh-Moosavy, Eng. Ali Rasouli,
Volume 7, Issue 2 (Journal OF Welding Science and Technology 2022)
Abstract
In this research similar joining of NiTi shape memory alloy was studied. For this purpose, NiTi alloy in the form of wires with circular cross section possessing martensitic phase structure at room temperature was used. By utilizing Nd:YAG pulsed laser welding method followed by optimizing its technical parameters, a defectless joint in terms of appearance and metallurgical properties was obtained. In the next step, the effect of various pulsed laser duration time on properties of the obtained similar joint of NiTi was investigated. Moreover, the resultant microstructures were studied using optical microscope (OP) and Scanning Electron Microscope (SEM) equipped with chemical analysis of EDS. Furthermore, the samples prepared under different pulsed laser duration time conditions were characterized by using tensile and micro-hardness tests. Investigating the results of the performed evaluations revealed that higher levels of heat input has resulted in grain growth, dissolution of precipitations as well as reduction in hardness and ultimate tensile strength of the samples in the joint zone.
M. Foumani, H. Naffakh-Moosavy, A. Rasouli, H. Aliyari,
Volume 8, Issue 1 (Journal OF Welding Science and Technology 2022)
Abstract
Surface roughness in the welding processes is one of the important parameters in the laser welded metal connections which affects laser beam absorption directly. When the laser beam is irradiated to the surface of the base metal, the surface roughness plays an important role in the amount of beam absorption and the amount of melting achieved and directly affects the penetration depth. The main purpose of this study is to investigate the effect of roughness mentioned above in the equal parameter for this widely used aluminum alloy. Microstructural Surveys were performed on three different roughness levels of the sample and the results obtained from the analysis of samples by optical microscope (OM), atomic force microscope (AFM) and Scanning electron microscopy (SEM) analysis showed that, increasing the surface roughness up to Ra = 0.16 micrometer, caused the greater degree of beam engagement by the surface grooves, hence more concentration of the beam photons and more melting obtained, so the depth of penetration increases by consuming a lower amount of energy.
A. Ardalani, H. Naffakh-Moosavy,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
In this research, the effect of temperature and time parameters are investigated on the microstructure and mechanical properties of dissimilar brazing of 17-4 PH stainless steel and Ti-6Al-4V alloy with BNi-2 filler metal. The microstructure of the joint is evaluated with optical and scanning electron microscopes and the mechanical properties of the joint are also evaluated with tensile-shear and microhardness tests. It can be seen that at a constant temperature of 1050°C, increasing the time from 15 to 30 minutes decreases the shear strength from 34.66 to 29.39 MPa. Formation of brittle intermetallic compounds like NiTi2 and FeTi2 increase strength and promote brittle fracture.At a fixed time of 15 minutes, increasing the temperature from 1050 to 1100 °C causes the strength to increase from 34.66 to 38.46 MPa. Also, the increase in temperature and time increases the ISZ thickness formed in the joints on the side of the filler metal - Ti-6Al-4V from 41.40 to 81.48 microns. The increase in temperature and time also causes more diffusion of boron into the SS-filler joint, which forms various boron compounds and widens this region.
