Showing 5 results for Khorram
A. Khorram, A. Davoodi Jamalooei, A. Jafari,
Volume 3, Issue 2 (Journal OF Welding Science and Technology of Iran 2018)
Abstract
In this study, microstructural evaluation and mechanical properties of similar TLP bonded of Inconel 600 by using of BNi-2 interlayer were investigated. The bonding tests were carried out at 1050°C and 1100°C for 5-45 min which homogenization treatment was performed on the best of the bonded samples. Results showed that Ni-B eutectic compound was formed in the a-thermally solidification zone (ASZ) of the bonded sample at 1050°C. In addition to existence of the Ni-B compound, Cr-B was observed in the ASZ of the bonded sample at 1100°C. Ni-B and Ni-Cr-B were formed in the diffusion affected zone (DAZ). TLP bonded sample at 1050°C for 45min including discontinuous areas of ASZ in isothermal solidification zone (ISZ) was the best bonded sample. Homogenization process was carried out on this sample caused to elimination of the eutectic compounds, completely. Mechanical investigation revealed that due to existence of the intermetallic compounds in the ASZ and DAZ, value of hardness for this region were about 510 and 311 HV, respectively. Whit elimination of the intermetallic compounds by performing of homogenization treatment, mechanical properties of the boding region were improved.
A. Mahdavi Shaker, H. Momeni, A. Khorram, A. Yazdipour,
Volume 8, Issue 2 (Journal OF Welding Science and Technology 2023)
Abstract
This study aimed to investigate the effect of electron beam welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between 17-4PH precipitation hardening stainless steel and Ti6Al4V alloy. For this purpose, the welding of these two alloys was done without an interlayer and with an interlayer of copper with a thickness of 0.8 mm. Two different welding speeds of 0.7 and 0.9 m/min with four levels of beam offset (0, 0.2, 0.4 and 0.6 mm) from the center of the interlayer towards the steel were used to perform experiments. The results show that in the direct welding of titanium and steel, the joint structure consists of TiFe and TiFe2+TiCr2 intermetallic compounds with high hardness (about 900 Vickers). In the welding of titanium and steel by using the copper interlayer, the structure in the weld pool and the interface between the weld pool and steel includes a solid solution of copper and TiFe2 intermetallic compounds, and at the interface between the weld pool and titanium includes Ti+Ti2Cu and TiFe. The hardness of the welding zone in the samples welded with copper interlayer is about 400 Vickers. The highest value of hardness is observed at the interface between the weld pool and titanium alloy, as well as at the interface between the weld pool and steel, which is due to the presence of intermetallic compounds with high hardness. By increasing the welding speed and beam offset, the hardness decreases, which is due to the reduction of brittle intermetallic compounds in the joint structure. The welded sample with a welding speed of 0.9 m/min and beam offset of 0.6 mm has the highest shear strength equal to 160 MPa.
A. Mahdavi Shaker, H. Momeni, A. Khorram, A. Yazdipour,
Volume 9, Issue 1 (Journal OF Welding Science and Technology 2023)
Abstract
This study aimed to investigate the effect of electron beam welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between 17-4PH stainless steel and Ti6Al4V alloy. For this purpose, the welding of these two alloys was performed with an copper interlayer with a thickness of 1 mm. Two different welding speeds of 0.7 and 0.9 m/min with four levels of beam offset (0, 0.2, 0.4 and 0.6 mm) from the center of the interlayer towards the steel were used to accomplish the experiments. The results show that by using the copper interlayer with thickness of 1 mm, the cracks caused by the formation of intermetallic compounds are removed from the weld pool. At the interface between the titanium and the weld pool, at the beam offset of 0 and 0.2 mm, a solid solution of copper and TiCu2 intermetallic compounds is formed, while at the beam offset of 0.4 and 0.6 mm, a solid solution of copper and TiCu intermetallic compounds is formed. The weld pool, at the beam offset of 0 and 0.2 mm, consists of TiCr2+TiFe2 intermetallic compounds while at the beam offset of 0.4 and 0.6 mm, solid solution of iron (α-Fe), solid solution of copper and TiCu intermetallic compounds are formed. The highest value of hardness is observed at the interface between the weld pool and the titanium alloy, as well as at the interface between the weld pool and the steel, which is due to the presence of intermetallic compounds with high hardness in these regions. By increasing the welding speed and the beam offset, the hardness value decreases, which is due to the reduction of brittle intermetallic compounds in the joint structure. By increasing the beam offset from 0.4 mm to 0.6 mm at the speed of 0.7 m/min, the shear strength increases from 180 MPa to 210 MPa and at the speed of 0.9 m/min, the shear strength raises from 230 MPa to 250 MPa. The welded sample with the welding speed of 0.9 m/min and the beam offset of 0.6 mm has the highest shear strength equal to 250 MPa. The failure in all samples happened at the interface between the weld pool and the titanium alloy, which shows that the weakest region in the joint is this interface.
A. Gandomdoust, M. Sarkari Khorrami, S. F. Kashani-Bozorg, H. Ghorbani,
Volume 9, Issue 1 (Journal OF Welding Science and Technology 2023)
Abstract
As one of the important pillars of the fourth industrial revolution, metal additive manufacturing (AM) technologies provide a disruptive approach to digital manufacturing. Laser powder bed fusion (LPBF), as one of these technologies, has great potential in producing geometrically complex and high-performance parts. In recent years, the manufacturing of aluminum alloy parts using this technology has attracted much attention. However, their manufacturing still faces some challenging issues. One of the most serious issues encountered in the manufacturing of aluminum alloys, especially high-strength grades, is solidification cracking. In the present investigation, the formation mechanisms of solidification cracking, and the associated effective factors were reviewed. Controlling the solidification microstructure and grain refinement, using the addition of small quantities (<1 wt.%) of micro- or nano-sized particles to the initial alloying powder, was suggested as the most effective method for reducing solidification cracking. These particles act as nucleation sites, prevent grain growth, pin grain boundaries, and with the help of factors that provide constitutional supercooling can effectively minimize solidification cracking. Eventually, effects of various additives in grain refinement and their associated mechanism in reduction of solidification cracks of high-strength aluminum alloys by LPBF is presented.
Ali Khorram, Hassan Habibi, Alireza Yazdipour,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
This study aimed to investigate the effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between 418 steel and Inconel 738 superalloy using Ni interlayer with a thickness of 50 µm. The experiments were performed in a vacuum furnace at three temperatures of 1000, 1050 and 1150 °C for 45, 60, 75 and 90 min under the pressure of 5 MPa.The results show that voids and non-bonded areas are seen in the samples that were bonded at a lower temperature (1000 °C). By increasing the joining temperature from 1000 °C to 1050 °C, all micro discontinuities have disappeared, which shows that the microplastic deformation of roughness has improved. Then, by increasing the temperature to 1150 °C, non-bonded areas are observed in the joint due to the reduction of pressure on the contact surfaces. When pure nickel is used as an interlayer, intermetallic compounds of γ' [Ni3(Al, Ti)] are formed in the γ matrix phase on the side of Inconel 738 superalloy while compounds of FeNi3 and γ (γFe, Ni) are formed on the side of 418 steel. According to the results of line scan analysis, the slope and penetration of elements in Inconel 738 superalloy is lower than 418 steel, which indicates less penetration in Inconel 738 superalloy. In the sample welded at the temperature of 1050 °C and the time of 90 Min, the penetration value of the nickel interlayer in 418 steel and Inconel 738 superalloy was 40 µm and 35 µm, respectively. By comparing the maximum hardness, it can be concluded that the joint at the temperature of 1050 °C and the time of 90 Min has a lower maximum hardness than other samples. Therefore, it has better joint characteristics than other samples in terms of intermetallic compounds. The highest value of shear strength was obtained at the temperature of 1050 °C and the time of 90 Min, which is equal to 270 MPa.
