SEARCH RESULT

In this study, isothermal annealing was performed to C70 quality steel sheet in a salt bath at 250 °C and 350 °C for 10 s, 1 min, 10 min, and 60 min after austenitizing performed at 850 °C for 150 s and the samples were then tempered at 415 °C for 150 s. Effect of these heat treatments on microstructure, hardness and bending properties was then investigated. Results showed that the initial ferrite and pearlite microstructure generally transformed into martensite. Tempered martensitic microstructure was obtained after tempering heat treatment. Hardness of the samples has a decreasing tendency with increasing annealing times at a given annealing temperature. Tempering heat treatment decreases the hardness values obtained after isothermal annealing, as expected. However, hardness values after tempering did not exhibit a significant variation with respect to isothermal annealing time. As compared to original sample, the application of tempering after isothermal annealing increases bending strength, and bending strain also increases getting closer to values exhibited by the original sample.

International Iron & Steel Symposium
UDCS

Serdar Kuzkaya Yakup Yurekturk Faiz Muhaffel Murat Baydogan

Hot-dip aluminizing (HDA) process is an effective coating technique to protect the surface of steel and cast irons from corrosion, oxidation, decarburization and wear at high temperatures. Because of these advantages, HDA is used to protect the surface of steels used in the hot stamping process in automotive industry against oxidation and decarburization. Also, HDA can provide additional oxidation resistance to high silicon ductile irons used in high-temperature applications such as furnace parts and exhaust manifolds. HDA is generally performed by dipping the substrates into molten Al or Al–Si alloys. This process results in the formation of various Fe–Al intermetallics along the coating. For example, immersing the substrate into pure Al produces Fe2Al5 phase close to the substrate, and FeAl3 phase close to the surface. A high-temperature diffusion annealing after HDA provides interdiffusion within the coating and thus can change the type and order of the intermetallics. In this study, the effect of HDA on structural, morphological and mechanical properties of the coating formed on a low carbon steel, a stainless steel and a high silicon ductile iron were addressed. In addition, effect of successive application of HDA and austempering on wear and corrosion properties of the ductile iron was also discussed.

International Iron & Steel Symposium
UDCS

Murat Baydogan

Diamond cutting tools have been widely used in natural stone industry as the circular sawing, frame sawing, wire sawing and core drilling. The diamond cutting tools are manufactured by powder metallurgy techniques. They are consisted of diamond particles embedded in metal matrix. Chemical interaction between diamonds and matrix is primary importance for diamond cutting tools. As the most used binder to provide these reaction is iron and its alloys. The aim of this study is to enhance the cutting performance of diamond tools by the investigation the effects of iron addition on to the matrix compositions. In this study; 30,50 and 80 wt% Fe containing matrices were determined and their mechanical properties, microstructures and wear resistances were examined comparatively. All materials in the form of powders were cold pressed and then the pellets were sintered with Spark Plasma Sintering (SPS). Microstructural and mechanical characterizations were performed by SEM-EDS, XRD, hardness, compression tests and wear tests. According to the results, control on the grain size and reaching the theoretical density values were achieved by SPS method due the lower sintering temperature and shorter sintering time. Results showed that Fe additives had no negative effect on properties of the samples. Moreover, the mechanical properties of the samples increased with increasing Fe contents.

International Iron & Steel Symposium
UDCS

Berrak Bulut Murat Baydogan Eyup Sabri Kayali

CoCr alloys (ASTM F75) are well-known metallic biomaterial which is used in production of load bearing orthopaedic implants because of their superior mechanical properties [1,2]. Although this material has superior mechanical properties, low bioactivity and ion release as a result of tribological effects are limiting it’s wider applications [3]. Surface modification of this material to enhance it’s bioactivity and wear resistance is one of the hot topics in the literature [4,5].

International Symposium on Light Alloys and Composite Materials
UHAKS

Dogukan Cetiner Ahmet Hilmi Paksoy Onur Tazegul Murat Baydogan Hasan Guleryuz Huseyin Cimenoglu

The use of aluminum alloys in automotive industry has greatly increased in recent years. This has been attributed not only to the issues of fuel economy, but also to those of safety, resource conservation and environmental concerns [1]. High-strength age-hardened 7xxx series Al−Zn−Mg−Cu alloys are widely used for aircraft structures, where they are subjected to demanding operating conditions [2]. In this study, retrogression and reaging (RRA) heat treatment was applied to commercial 7075-T6 aluminum alloy (Al–Zn–Mg–Cu), whose chemical composition is shown in Table 1 RRA heat treatment is capable of producing a material with high strength and high corrosion resistance than presented by the T6 temper. In the retrogression treatment, salt bath furnace was used for heating the samples to 250°C and 280°C for 1 min. After that, the samples taking out of furnace and quenched in cold water of 5-8°C temperature. Subsequently intermediate deformations were applied to the samples in 2%, 4% and 6% and one sample was left undeformed for comparison. Following intermediate deformations, the samples were reaged at 120°C for 24 and then cooled to room temperature in air. In order to investigate effect of intermediate deformation on the strength and strain hardening exponent as the indicators of formability characteristics of RRA’ed 7075 alloys, tensile tests were carried out to determine yield strength, ultimate tensile strength and tensile strain hardening exponent (n-value). Hardness and electrical conductivity measurements were also performed on the samples. Variation of strength and elongation at fracture of the samples retrogressed at 250°C (a) and 280°C (b) and then reaged as a function of intermediate deformation is shown in Figure 1 It is obviously seen that strength values decrease whereas ductility (elongation at fracture) generally increases with increasing retrogression temperature. On the other hand, intermediate deformation has not any significant effect on strength and ductility for both retrogression temperatures. Figure 2 shows variation of strain hardening exponent of the samples retrogressed at 250°C and 280°C and then reaged as a function of intermediate deformation. It is very apparent that retrogression temperature has a strong effect on strain hardening exponent, whose value increases with increasing retrogression temperature. Figure 3 indicates variation of hardness and electrical conductivity of the samples retrogressed at 250°C and 280°C and then reaged as a function of intermediate deformation. It is obvious that hardness decreases whereas electrical conductivity increases with increasing retrogression temperature. It is well known that electrical conductivity is a good indicator of corrosion resistance of the samples [3]. Therefore, this can be said that corrosion resistance increases with increasing retrogression temperature, as expected. Overall results demonstrated that higher retrogression temperature is beneficial in the point of formability because it increases ultimate tensile strength to yield strength ratio and strain hardening exponent as well. In the view point of intermediate deformation, it was shown that it does not significantly effect of strength, hardness and electrical conductivity of the samples after RRA, but lead to some decrement in strain hardening exponent, which adversely affects the formability characteristics of 7075 RRA alloy.

International Symposium on Light Alloys and Composite Materials
UHAKS

Armin Rashidi Yakup Yurekturk Murat Baydogan

Mg and its alloys are commonly used in automotive, aerospace, biomedical, communication industries due to their superior properties such as high specific strength, low density, good electromagnetic shielding, superior damping capacity, machinability and recyclability. Nonetheless, low wear and corrosion resistances are the main drawbacks limiting extensive usage of magnesium alloys. Moreover, low melting point of magnesium limits wide-range of applications at elevated temperatures [1,2].

International Symposium on Light Alloys and Composite Materials
UHAKS

Ekin Selvi Faiz Muhaffel Murat Baydogan

Titanium based materials have wide range of applications at elevated temperatures including highly oxidizing and corrosive service conditions. Even though natural oxide film of titanium is very stable at room temperature and resistant to corrosion and oxidation, it is very brittle at temperatures higher than 650°C. Therefore, a protective layer at the surface would provide increased lifetime and performance for titanium based materials [1, 2]. For this purpose various methods including Al films sputtering, magnetron sputtering, pack cementation, pack aluminizing have been researched so far. Amongst these methods, hot dip aluminizing is a promising method for coating titanium materials as it is a simple, quick and inexpensive alternative with respect to the other methods [3,4].

International Symposium on Light Alloys and Composite Materials
UHAKS

Mert Altay Yakup Yurekturk Murat Baydogan

β-type titanium alloys have been developed all over the world, which widely used in several biomedical applications because of their good mechanical properties such as low Young’s modulus and corrosion resistance [1]. Niinomi et al. has also developed a β-type Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ, which is composed of non-toxic and non-allergic elements such as Nb, Ta, and Zr, with low Young’s modulus [2]. It was also revealed that the cell viability on TNTZ is much superior than that on Ti-6Al-4V ELI [2,3]. Young’s modulus of TNTZ subjected has been found to be around 60 GPa at the microstructure having single β (BCC) phase for solution treatment and cold rolling [4-5]. It is much more closer to those (10-30 GPa) of bone than those (100 and 110 GPa) of commercial pure Ti and Ti-6Al-4V ELI.

International Symposium on Light Alloys and Composite Materials
UHAKS

Hakan Yilmazer Mazin Abed Mitsuo Niinomi Masaaki Nakai Huseyin Cimenoglu Murat Baydogan