Mehmet Turker

Thermal, Mechanical and Electrical Properties of High Density Polyethylene Composites Reinforced with Copper Powder

The thermal conductivity, electrical conductivity and mechanical properties such as tensile strength, elongation, modulus of elasticity, were experimentally investigated. Thermal and electrical conductivity measurements were performed up to filler concentration of 30 vol.%. The mechanical properties of high density polyethylene filled with up to 30 vol.% Cu particles were investigated. The tensile strength, elongation and toughness decreased with increasing Cu powder content. This was attributed to the introduction of discontinuities in the polymer structure in which modulus of elasticity increased with increasing the copper content.

The effect of production parameters on the foaming behavior of spherical-shaped aluminum foam

The effect of production parameters on the foaming behavior of spherical-shaped aluminum foam was studied. Elemental powders of Alumix 231 and 1% TiH2 were mixed, compacted at 600 MPa pressure by using a uniaxial action press to produce blanks with 50×30×10 mm in dimensions. These blanks were pre-heated at 550 °C in a furnace for 180 min and then deformed by 10, 30, 50 and 70% by using an eccentric press. They were cut into square shape and foamed at temperatures between 650 °C and 710 °C. It was experimentally found that, the volume expansion rate of foam increases but the maximum foaming duration decreases with increasing the deformation rate and foaming temperature. In these studies 70% deformation and 3.5 minutes foaming duration were found to be the best for the production of spherical foams. This was determined by obtaining the maximum expansion, lower density and homogeneously distributed pores with spherical foams. It was also found that 10% deformation rate was not enough for foaming.

The investigation of mechanical properties of B4C-reinforced AlSi7 foams

Abstract In this study, the mechanical properties of B4C-reinforced AlSi7 foams produced by using a powder metallurgy method were investigated. For this purpose, Al foams containing B4C at various ratios (0, 2, 4 and 6 %) were prepared with dimensions of 30 × 30 × 14 mm and 110 × 15 × 14 mm for compression and bending tests. Both tests were performed at a 1 mm min–1 strain rate. According to the experimental results, the compressive stress of B4C-reinforced/unreinforced AlSi7 foams, whose relative densities were close to each other, for 10 % strain increased about 15 % with the addition of B4C. Although energy absorption values of B4C-reinforced/unreinforced AlSi7 foams were in a complex correlation for 60 % strain, the amount of absorption energy increased with the increase in relative density and the amount of B4C. Bending strength increased due to strain hardening that occurs with the addition of B4C to AlSi7 foams. While maximum bending strength was 0.9 kN in unreinforced materials, it was ∼1.15 kN in 6 % B4C-reinforced AlSi7 foams. Thus, the bending strength of B4C-reinforced materials is higher by ∼ 28 %.

Diffusible hydrogen content in submerged arc welds of a S960 type steel

Abstract Hydrogen induced damage is a dangerous phenomenon affecting the weld quality with regard to construction service life even without visible indication. The determination of diffusible hydrogen in weld metal has been standardized at an international level in ISO 3690:2012. This international standard specifies the sampling and analytical procedure for the determination of diffusible hydrogen in martensitic, bainitic and ferritic steel weld metal which arises from the welding of such steels using arc welding processes with filler metal. In this study, S960QL steel is extensively used in the heavy transport, lifting and mining industry, where mobile or fixed structures have to carry high loads – often in safety critical situations. In order to sustain extreme characteristics of these high strength low alloy steels, it is a must to reduce the manufacturing defects. In the investigations presented in this paper, the influence of arc length on the weld metal hydrogen concentration was studied according ...Abstract Hydrogen induced damage is a dangerous phenomenon affecting the weld quality with regard to construction service life even without visible indication. The determination of diffusible hydrogen in weld metal has been standardized at an international level in ISO 3690:2012. This international standard specifies the sampling and analytical procedure for the determination of diffusible hydrogen in martensitic, bainitic and ferritic steel weld metal which arises from the welding of such steels using arc welding processes with filler metal. In this study, S960QL steel is extensively used in the heavy transport, lifting and mining industry, where mobile or fixed structures have to carry high loads – often in safety critical situations. In order to sustain extreme characteristics of these high strength low alloy steels, it is a must to reduce the manufacturing defects. In the investigations presented in this paper, the influence of arc length on the weld metal hydrogen concentration was studied according to the ISO DIS 3690 in S960QL type steel with submerged arc welding. Measurement of the diffusible hydrogen was carried out by means of carrier gas hot extraction method. The weld seams with different arc length have similar chemical compositions. Maximum hardness values in the range of 410–425 HV1 were measured in the HAZ on both vertical and horizontal rows in welded structure with two mm wire diameter due to recrystallization condition. For four mm wire diameter, the hardness decreasing which is depending on the grain coarsening in the welded samples with two mm was not occurred in the weld seam-HAZ interface. The larger weld pool and the long arc length increased possibility of hydrogen pick-up and absorbing. Because of this reason, the diffusible hydrogen contents in the welded structure increased in accordance with the arc length.

Effect of Cutting Tool Materials on Surface Roughness and Cutting Forces in Machining of Al-Si3N4 Composite Produced by Powder Metallurgy

In this study, aluminum-based composites reinforced with various amounts of α-Si3N4 were produced by powder metallurgy (P/M). The machinability properties of MMCs were determined by means of cutting forces and surface roughness. Machining tests were carried out by using PCD and K10 cutting tools. Increasing of Si3N4 volume fraction in the matrix resulted in a decrease of the surface roughness and turning forces. PCD cutting tools showed better cutting performance than K10 tools. Surface roughness and turning forces were decreased significantly by PCD tool.

Mechanical and ballistic properties of powder metal 7039 aluminium alloy joined by friction stir welding

Abstract 7039 Al alloy plates which were used as armor materials were produced by powder metallurgy method. The prepared mixed powders were pressed and plated by extrusion process. These plates, after being subjected to T6 heat treatment, were joined double-sided by friction stir welding method. Microstructure and microhardness of the welded plate were investigated. It was determined that the finest grain structure and the lowest hardness value occurred in the stir zone as 2–6 μm and HV 80.9, respectively. In order to determine the ballistic properties of welded plates, 7.62 mm armor piercing projectiles were shot to the base metal (BM), heat affected zone (HAZ), and thermomechanically affected zone+stir zone (TMAZ+SZ). Ballistic limits ( v 50 ) of these zones were determined. The ballistic limits of the BM, TMAZ+SZ, and HAZ of the plate were approximately 14.7%, 15.3%, and 17.9% lower than that of the standard plate at the same thickness, respectively. It was determined that the armor piercing projectiles created petaling and ductile hole enlargement failure types at the armor plate. Ballistic and mechanical results can be enhanced by hot–cold rolling mills after extrusion and particle reinforcement.

Investigation of mechanical properties of tubular aluminum foams

Abstract This manuscript focuses on the mechanical behavior under compressive and bending loadings of tubular aluminum foams. The tubular structures were manufactured using the powder metallurgy technique. Tubular aluminum foams were fabricated by heating foamable precursor materials above their melting temperature in a mould. The influence of important parameters such as wall thickness and density of foam on the mechanical properties was investigated. It was found that the 6 mm thick specimen showed a lower collapse strength than the thicker 9 mm specimen. Despite the decrease in densities of the samples, the collapse strength increased with the increase in wall thickness. The reduction of approximately 33% in wall thickness (from t = 9 mm to 6 mm) decreased the bending performance of the tubular aluminum foams by approximately 50%.

Friction stir welding of foamable AlSi7 reinforced by B4C

Abstract Friction stir welding was successfully performed on B4C-reinforced foamable AlSi7 materials produced via a powder metallurgy route. Starting materials of 1 wt.% TiH2, 7 wt.% Si and 6 wt.% B4C were mixed with aluminum matrix powder. Mixed powders were then pressed, extruded and rolled for the production of foamable materials. Microstructural and macrostructural examination along with microhardness and tensile tests were performed to evaluate the weld zone characteristics of foamable materials welded by friction stir welding. Tunnels or needle-shaped gaps were observed in the macrostructures of the weld zones of samples joined at 1 250 rpm and 2 000 rpm rotational speeds. Moreover, the rough surface in the welding zone of materials decreased with increasing rotational speed. Defect-free joints were observed for samples at 1 600 rpm rotational and 40 mm min−1 traverse speeds. There was no significant difference between the microstructures of the weld zone and the base material in terms of particle size and distribution. It was observed that the B4C particles in the nugget zone were partly directed or clustered as a result of the physical mixing. Ultimate tensile strength values of B4C-reinforced foamable AlSi7 materials joined by friction stir welding were found to be lower compared to the base material. The maximum ultimate tensile strength of 135 MPa was obtained at a 1 600 rpm rotational speed and 40 mm min−1 traverse speed. The minimum tensile strength in the samples of 95 MPa was obtained at a 1 250 rpm rotational speed and 80 mm min−1 traverse speed. In all welding conditions, the hardness in the nugget zone increased compared to the base material.

Effect of welding parameters on the mechanical properties of GMA-welded HY-80 steels

Abstract In this publication, investigations of HY-80 steels joined by gas metal arc welding by using different welding parameters are described. Different samples obtained from the welded joints were subjected to mechanical testing by means of tensile, hardness and impact toughness tests. The tensile test results showed that the strength of weld metal and heat affected zone were higher than of base metal. Similar Charpy impact toughness test results were obtained for weld metal and heat affected zone. Weld metal hardness was almost similar to the base metal hardness, nevertheless, the heat affected zone indicated higher values. The base metal has ferritic-perlitic structure with fine grains. Martensite needles and bainite are seen in the heat affected zone. Weld metal has martensite needles, partial bainite and residual austenite.

ALSİ7 KÖPÜKLERİN GÖZENEK MORFOLOJİSİ ÜZERİNE B4C İLAVESİNİN ETKİSİ

Bu calismada toz metalurjisi yontemi ile uretilmis AlSi7 kopuklerin gozenek morfolojisi uzerine B 4 C ilavesinin etkisi incelenmistir. Bu amacla Al icerisinde % 1 TiH 2 , % 7 Si ve degisik oranlarda (% 2, 4 ve 6) B 4 C tozlari ilave edilerek karistirilmistir. Daha sonra karisim tozlar 400 MPa altinda sikistirilmistir. Elde edilen blok numuneler ekstruzyon ve haddeleme islemlerinden gecirilerek kopurebilir malzemeler uretilmistir. Uretilen numuneler farkli sicakliklarda (690, 710, 730 ve 750 °C ) serbest halde kopurtme islemine tabi tutulmustur. Deneysel sonuclara gore; dusuk kopurtme sicakliklarinda B 4 C takviyeli numuneler, parcacik icermeyen numunelere oranla daha dusuk hacimsel genlesme sergilemistir. Genlesme degerleri kopurtme sicakligindaki artisa bagli olarak artmistir. Numunelerin tamamina yakininda 750 °C kopurtme sicakliginda maksimum oranda hacimsel genlesme degerleri (% 350 - % 400) elde edilmistir. B 4 C miktari ve kopurme sicakliktaki artis ile birlikte numunelerde kuresellik faktoru ve gozenek boyutlarinin arttigi, gozenek sayisinin ise azaldigi tespit edilmistir.