Papers by Author: Ibrahim M. Ghayad

Abstract: The influence of recrystallization annealing on the microstructure, mechanical properties and corrosion behaviour of an austenitic TWIP steel bearing medium Mn and V alloying was investigated. The steel undergone a heavy cold deformation of 65 % reduction. Subsequently, recrystallization annealing at 1000 °C and 1100 °C for 15 min was conducted to achieve different grain structures. The microstructural evolution was studied using optical microscopy and electron backscatter diffraction technique. Mechanical properties were determined using tensile tests at room temperature. Corrosion behaviour was measured by cyclic potentiodynamic polarization at 3.5 pct NaCl. For comparison, austenitic stainless-steel Type 201 was used in this study. It was observed that at 1000 °C, a non-uniform austenitic grain structure with vanadium carbides distributed throughout the matrix was obtained. However, a coarse grain structure without carbides was induced at 1100 °C. The fine-grained structure enhanced at 1000 °C exhibited higher strength and good ductility. Contrary to this, the corrosion results showed that a significant deterioration in the corrosion resistance could be observed in sodium chloride solution for the achieved structure at 1000 °C compared to 201 stainless steel.

Abstract: This article reports the corrosion behavior of 904L weldment in sulfuric acid as a strong corrosive media. The corrosion behavior was studied by total immersion tests and potentidynamic polarization test. Total immersion test has been conducted at different acid concentrations typically: 1, 2, 4, 6, 8 and 18.4 M at 25°C. The effect of temperature (25- 100°C) on the weight loss measurements of the alloy samples was followed in the 4 M acid solution. On the other hand, potentiodynamic polarization tests were conducted in 2,5, 8 and 18.4 M H₂SO₄ solution. The potentiodynamic polarization test was also conducted in the practically used leaching medium (2 M H₂SO₄ + 10% monazite).Results show that the weight loss increases with the increase of acid concentration and reaches its maximum at 4 M H₂SO₄ and then gradually decreases. Meanwhile, the rise in temperatures results in the increase of weight loss. Potentiodynamic polarization tests indicate that the 5 M acid solution gives the highest corrosion rate of 0.6399 mm/Y. The leaching medium shows relatively higher corrosion rate (0.124 mm/y) than the corresponding 2 M H2SO4 without monazite (0.01712 mm/y).

Abstract: Ti-12Mo/ZrO₂ nanocomposites are fabricated using the powder metallurgy technique for the potential of aerospace applications. Titanium-12 wt. % molybdenum metal matrix composite containing various percentages of ZrO₂ (5, 10, and 15 wt. %) are prepared. The phase composition and microstructure of Ti-12Mo/ZrO₂ powder, as well as the consolidated composites), are investigated by both X-ray diffraction and scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) respectively. All the consolidated composites are characterized by measuring the density, Vickers hardness, and wear rate. XRD refers to no new phase are formed between Ti, Mo, and ZrO₂ during the sintering process. Also, a good microstructure is achieved. Results indicated that the density of the sintered composites is increased with increasing ZrO₂ percent up to 5 wt. %. On the other hand, the highest hardness and highest wear resistance are achieved for 5 wt. % ZrO₂ sample. The present work demonstrated that Ti-12Mo/ZrO₂ composites have a high potential for aerospace applications.

Abstract: Stainless steel AISI 304 was laser treated to enhance corrosion resistance and improve surface properties. . This alloy has many applications in auto industry (car body,) as well as oil and gas industry. Different conditions were applied in the laser surface treatment, namely: laser power density, scan speed, distance between paths, medium gas (air, argon and nitrogen). After laser treatment, the samples microstructures were investigated using optical microscope to examine micro structural changes due to laser irradiation. Specimen surfaces were investigated using XRD, SEM and EDAX before and after laser treatment to examine the surface composition changes brought by laser irradiation. Results showed that laser irradiation enhances the corrosion resistance of AISI 304 Stainless steel to a large extent. Corrosion rates as low as 0.011 mpy for laser treated samples were obtained in comparison to 0.952 mpy obtained for the untreated samples. Superior pitting corrosion resistance was obtained under specific treatment conditions. The enhancement of corrosion resistance depends on the laser irradiation conditions. The corrosion protection afforded by laser treatment is attributed mainly to the grain refinement of the top surface layer. This layer is found to consist of nano-scale grains.