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Öğe Effect of aging temperature and martensite by volume on strain aging behaviour of dual phase steel(Taylor & Francis Ltd, 2008) Guenduez, S.; Demir, B.; Kacar, R.A study has been made of the cold deformation aging susceptibility of dual phase steel with 14 and 22% martensite by volume. It was found that yield strength (YS) and ultimate tensile strength (UTS) increased with increasing testing temperature up to 200 degrees C and then decreased at 250 degrees C which indicated that static strain aging is dominant up to 200 degrees C. This aging is associated with free dislocations in the ferrite as a result of the austenite-martensite transformation, which become preferential sites for solute atom diffusion. At higher temperature (250 degrees C) a softening effect is dominant due to tempering of martensite. It was also observed that at a given aging temperature YS, UTS and Delta Y (increase in stress due to strain aging) increased with by volume of martensite.Öğe FRICTION STIR SPOT WELDABILITY OF Al-Cu-Al MATERIAL COUPLE(Gazi Univ, Fac Engineering Architecture, 2011) Kacar, R.; Emre, H. Ertek; Demir, H.; Guenduez, S.Recently joining of metallic materials has gained a big importance. The problem can arise joining of advanced and new materials especially in industry. Thus, the solid state bonding methods have become much more popular effective in joining such materials. One of them is friction stir spot welding. In this study, 5754 quality aluminum couple using interlayer copper were joined by friction stir spot welding method using 1000 and 1600 rpm pin rotation for 3 and 5 second time intervals. The mechanical and metallurgical properties of weldment determined. The finding from this study compared with result that was obtained from FSSW Al-Al couple. The mechanical properties of FSSW welded Al-Cu-Al couple found better than Al-Al weldment.Öğe Increasing the strength of AISI 430 ferritic stainless steel by static strain ageing(Redakcia Kovove Materialy, 2009) Kacar, R.; Gunduz, S.In this study, the strain ageing behaviour of AISI 430 ferritic stainless steel is investigated. A certain part of the as-received ferritic stainless steel test pieces was pre-strained for 5 % in tension, then aged at 100, 200, 300, and 400 degrees C for 30 min in a furnace. The other part was solution heat-treated at 950 degrees C for 15 minutes, water quenched and pre-strained for 2 or 5 % in tension, then aged at 100, 200, 300, and 400 degrees C for 30 min. UTS (ultimate tensile strength), Delta Y (increase in yield strength due to strain ageing), percentage elongation and yield point elongation measurements were employed to investigate the effect of strain ageing on the mechanical properties. The experimental work has revealed that different ageing temperatures significantly affect the mechanical properties of the AISI 430 ferritic stainless steel.Öğe An investigation on the explosive cladding of 316L stainless steel-din-P355GH steel(2004) Kacar, R.; Acarer, M.In this study, 316L stainless steel and DIN-P355GH grade vessel steel were cladded by explosive welding technique. Microstructure, hardness and tensile shear strength, and fracture toughness of the cladded metals were evaluated. The bond interface of the cladded metals shows a wavy morphology. The hardness was increased in the parent and flyer plate near the bond interface while a general decrease was observed in both parent and flyer plate away from welded interface. Tensile shear test results showed that the bonding is acceptable. The impact toughness of the cladded metals at a given test temperature is found significantly higher than that of parent plate alone because of the high impact toughness of 316L austenitic stainless steel layer. Consequently, mechanical properties of the low-carbon steels can be increased by explosive cladding with austenitic stainless steel. © 2004 Elsevier B.V. All rights reserved.Öğe Microstructure and property relationships in resistance spot weld between 7114 interstitial free steel and 304 austenitic stainless steel(2006) Hasanbasoglu, A.; Kacar, R.Due to the differences in physical, chemical and mechanical properties of the base metals, the resistance spot welding of dissimilar materials is generally more challenging than that of similar materials. The influence of the primary welding parameters affecting the heat input such as peak current on the morphology, microhardness, and tensile shear load bearing capacity of dissimilar welds between 304 grades austenitic and 7114 grade interstitial free steel has been investigated. The optimum welding parameters producing maximum joint strength were established at a peak current of 9 kA, where the electrode force is kept 6 × 10-5 Pa and weld time is kept constant 17 cycles respectively. The primary cause of weakening the weldment is identified as the excessive grain growing region of heat affected zone (HAZ) in case of 7114 grade interstitial free steel.Öğe Resistance Spot Weldability of Deformed TRIP800 Steel(Amer Welding Soc, 2016) Emre, H. E.; Kacar, R.In order to simulate automotive manufacturing conditions, the spot weldability of cold -deformed, in tension by 10%, TRIP800 steels was investigated in this study. Tensile shear strength and failure mode associated with button geometry and electrode indentations were also evaluated, and weld lobe was drawn for resistance spot-welded deformed TRIP800 steel. The microstructure of the weldment was evaluated and the hardness profile of the weldment was also determined. It was found that the properties of the weldment are directly related to parameters used for the process and deformation of base metal prior to welding. It was found that the button diameter and button size ratio of deformed TRIP800 steel spot welds should be at least 4vt and 0.14-0.30, respectively, for pullout failure mode, acceptable shear strength, and surface quality.Öğe Strengthening of 6063 aluminium alloy by strain ageing(Redakcia Kovove Materialy, 2008) Guenduez, S.; Kacar, R.In this study, the artificial ageing behaviour of 6063 Al-alloy is investigated. A certain part of the aluminium test pieces was solution heat treated (SHT) at 520 degrees C for 2 h, water quenched, then aged at 180 degrees C for 1, 3, 5, 7, 9 and 15 h and the other part was pre-strained for 2 % in tension shortly after the solution heat treatment (SHTP), then aged at 180 degrees C for 1, 3, 5, 7, 9, 15 h in a furnace. Tensile strength, flow stress at 3 %, microhardness and electrical conductivity measurements were employed to investigate the effect of artificial ageing on the mechanical properties of Al-alloy. The variations in ageing time have improved the mechanical properties of the 6063 Al-alloy, whereas the ductility has decreased. The experimental work has revealed that different ageing times at 180 degrees C play a very important role in the precipitation hardening process of the 6063 Al-alloy.
