Iranian Journal of Materials Forming
Volume:10 Issue: 2, Spring 2023

The “Iranian Journal of Materials Forming (IJMF)” is an international open access journal in the fields of materials deformation and forming processes, which was established at Shiraz University in 2014. The journal is pleased to receive papers from scientists and engineers from academic and industrial areas related to all manufacturing processes. In addition, all deformations, including the elastic and plastic behaviors of materials and deformations due to failure, are part of this journal’s field of interest. The quality and credibility of the journal have been ensured by appointing some of the most well-known professors in the world as members of its editorial board. In addition, the wide range of the selected referees in this issue is a sign of its scientific quality. It is a matter of pride that for the third year this journal has been successfully released quarterly and the second issue of the year was published in 2023.

The integral hydro-bulge forming (IHBF) process, also called shell hydroforming, is a die-less forming technique used to manufacture hollow parts from preforms made of sheet blanks cut and welded together. In this study, integral hydro-bulging of spherical vessels was investigated both numerically and experimentally. Numerical simulations were performed using Abaqus commercial software, and the numerical results were validated via comparison with those obtained from the experiments. The thickness distribution along the equatorial and meridian paths, sphericity of the formed vessel, and critical fluid pressure at which instability occurs were studied, and the effect of the number of lateral petals was investigated. For this study, an St12 steel sheet with a thickness of 0.8 mm was used to make a spherical shell with 12 lateral petals and a diameter of 400 mm. The results showed that the use of preforms with more lateral petals leads to a more uniform thickness distribution and shape accuracy in the formation of spherical vessels. Furthermore, by increasing the number of petals from 8 to 16, the thickness decreased by 4.2%. The maximum thickness reduction occurs in the 8-petal state, and the least thickness reduction occurs in the 12-petal state. The results show that the increase in the number of lateral petals leads to the increase in the critical fluid pressure. By doubling the number of lateral petals, fracture pressure increased by 74% consequently.

In this study, electrographite brushes were produced from petroleum coke and coal tar pitch via the powder metallurgy method, and the effect of petroleum coke particle size and applied compacting pressure were investigated on the green density, hardness and, the graphitization process. The results showed that an increase in the density of the raw sample and the hardness of the final product occurred due to a decrease in particle size by increasing the milling time up to 4 h. Additionally, an increase in both density and hardness of the sample was observed as the applied compacting pressure was increased up to 150 MPa, where no alteration in the obtained values was observed with a further increase in the applied pressure. As a result of increasing the milling time and applying the optimum pressure, the density of the raw sample increased to 1.41 g/cm³ and the hardness increased to 81 Shore C. The results also proved that the average particle size of the used petroleum coke and the applied compacting pressure do not have an influence on the graphitization process.

The effect of severe surface plastic deformation on the microstructure and tribological properties of CoCrWNi super alloy L605 was investigated. The surface of the annealed alloy was frictionally processed by a tungsten carbide tool with a tip radius of 5 mm under different sliding speeds of 500, 800, 1100, 1400, 1700, and 2000 mm/min for 2, 5, 10, 20, and 30 passes. Based on the results, applying friction hardening (FH) promoted the formation of the e-HCP (martensite) phase in the surface structure of the g-FCC alloy up to a depth of about 500 mm. The maximum surface hardness was observed at the sliding speed of 1700 mm/min and 30 passes, where the surface hardness increased by almost 100% (from about 320 HV to more than 635 HV). Pin-on-disk wear tests were carried out at room temperature, under applied pressures of 0.25, 0.5, and 1 MPa, for a sliding distance of 1000 m. According to the results, under low applied pressures, i.e. 0.25 MPa, the maximum wear resistance was observed in the sample FH-processed for 30 passes at 1700 mm/min. However, due to the formation of lateral microcracks on the surface of samples processed by high number of FH passes, under the applied pressure of 1 MPa, the lowest wear was observed in the 5-pass processed sample (1700 mm/min). The wear rate and average friction coefficient (AFC) of this sample were about 45% and 30% lower than those of the base (annealed) sample, respectively.

To investigate the effect of the different content of hydroxyapatite (HA) (5, 10, and 15 wt.%) on the tensile properties and deformation mechanism of the poly‏ methylmethacrylate (PMMA), tensile test at different strain rate (4.1×10-4, 8.3×10-4,1.66×10-3, 3.31×10-3, 8.275×10-3, and 16.6×10-3 s-1), microscopic evaluations were performed on the standard samples. The results of the tensile test showed that by adding HA to the PMMA, its strain rate sensitivity increased. The activation energy (ΔH) for chain fluctuation decreased from 56.42 to 37.81 J/mol as HA content increased from 0 to 15 wt.%. In addition, the active volume ( ) of the chain during the tensile test was measured indicating that its value decreased from 3.02 to 2.35 as HA content promoted from 0 to 15 wt.%. The results of microscopic evaluation showed that the deformation mechanism of PMMA during the tensile test was crazing and dispersity of craze depended strongly on the HA content.

In this study the effect of heat treatment temperature on the formation and dissolution of gamma-prime phase has been studied in Inconel 617. Since the working temperature of Inconel 617 is above 540°C, the samples were heat treated at different temperatures in a range between 550 to 850°C and simulations were performed at the same temperatures by the JMatPro software. It was found that the gamma-prime phase with different percentages (below 10%) would exist in the temperature range of 550 to 800°C. However, it would gradually decrease as the temperature increases and finally dissolve completely at temperatures over 800°C. The observations by metallography were in good agreement with the predictions made by the JMatPro software. The microstructure investigations using the optical and field emission electron microscopy showed that the gamma-prime phase exists at 650°C and 750°C, but its weight percent decreases with increasing temperature, so that at 850°C no gamma-prime can be detected.

In the present paper, two-stage refilled friction stir spot welding is used to join mild steel sheets with a thickness of 2 mm. Meanwhile, alumina and titanium oxide nanopowders are also introduced to the nugget to achieve superior mechanical properties. Two non-consumable tools are used with and without pins to weld and refill the keyhole, respectively. Before refilling, the keyhole is filled with nanopowders which are then distributed by the pinless refilling tool. Three parameters are investigated; the rotational speed of the welding tool and the rotational speed and dwell time of the refilling tool. The tensile test is used to evaluate the strength of the joints. The microhardness is measured in the welding zone to evaluate the powder distribution. The results suggest an increase in the joint strength by 42% and 18% with alumina and TiO2 as reinforcement, respectively. With a 31.94% contribution, the refilling tool rotational speed is the most effective input parameter affecting the joint strength. Considering the microstructure analysis and the microhardness test, the material flow pattern is mainly downward which results in the accumulation of the reinforcing powder in the lower sheet especially when a lower refilling tool rotational speed is used.