جستجوی مقالات مرتبط با کلیدواژه "آلیاژ تیتانیوم" در نشریات گروه "مواد و متالورژی"

Both Ti-6Al-4V and 316L stainless steels are widely used as engineering alloys in many modern industries, especially aerospace, gas turbine engines and heat exchangers due to high mechanical properties, high creep, fatigue, and corrosion resistance. Fusion welding of these alloys is not easily possible due to their incomplete solubility in each other. Brazing is one of the best choices for joining dissimilar alloys. Infrared brazing is a novel process characterized with a high heating rate up to 500 °C/min. Accordingly, it is expected that both erosion of the substrate and excessive growth of intermetallic phases in the brazed joint are significantly decreased. This study is focused on the infrared brazing of Ti-6Al-4V and 316L stainless steel to investigate the influence of brazing parameters (brazing alloy, temperature and time) on microstructure and mechanical properties of base metals with CBS 34 (Ag-based) braze filler foils. Brazing was performed in a home-made infrared furnace at temperatures of 750, 780, 800, 850 and 900 °C for 3-5 min. Qualities of the brazed joints were evaluated by microstructure and phase constitution of the bonded joints with light optical microscope (LOM) and scanning electron microscope (SEM). Mechanical properties of the brazed joints were evaluated by hardness test. The optimum brazing parameters were at 850 °C-5 min for CBS 34 filler foils.

In this study by applying plasma electrolytic oxidation (PEO) coating on titanium alloy Ti-6Al-4V its fatigue behavior was studied. The results were compared in the presence or absence of the coating. Scanning electron microscopy (SEM) were used to determine the chemical composition of different phases as well as analyzing the microstructure and cracks’ nucleation and propagation and the coating hardness was measured by micro hardness tester. Fatigue test results showed that the fatigue life of the uncoated specimens was longer than the coated specimens. Comparing the images of the fracture surface of the coated specimens and the uncoated specimens in the same surfaces showed that the nucleation of fatigue cracks was appeared in one area in the uncoated specimens while the nucleation of fatigue cracks in coated specimens appeared in multiple areas. According to the microscopic images the coated surface had many pores which causes the nucleation to begin with the coating. The results of the test micro surveys of coverage shows that the hardness of the coating over the layer below it and makes it crack initiation of coverage to begin.

In this research، Ti-6Al-4V alloy was brazed with 410 stainless steel by three different filler metals as silver-base، nickel-base، and titanium-base alloys. In order to obtain optimum clearance، brazing was done in three different clearances of 0. 02، 0. 04 and 0. 06 mm. Also، the strength and hardness of the brazing zone were investigated. The results of shear strength showed that the brazed samples with titanium-base alloy at the clearance of 0. 02 mm had the maximum strength among the different samples which was 149. 5 MPa.