Hülya Durmuş

Weldability of AL99—SiC Composites by CO2 Laser Welding

In this study, Al99—SiC composites were produced using PM method. In the composites produced, the reinforcement rates of SiC were 0, 5, 10, and 20 (%wt). The matrix Al 99 powders were mechanically mixed with SiC particulates. These powders were compacted at room temperature at 500 MPa for 5 × 10 × 60 mm specimens and followed by sintering at 600 and 620°C for 1 h. Composite specimens were joined by CO2 laser welding method. Rofin—Sinar SM2000 machine was used for the welding process. The microstructure of melted region was investigated by optical, scanning, and X-ray microchemical analysis techniques. The hardness test, tensile test, and three-point bend test results were presented. The effect to CO2 laser welding method at different reinforcement rates and different sintering temperatures in Al 99 powder was investigated. Because of the lower thermal conductivity of Al99—SiC composites, melting zone is wide. It was observed that 0.5 m/min laser welding velocity was suitable for composites with low SiC ra...

Artificial Neural Network (ANN) Approach to Hardness Prediction of Aged Aluminium 2024 and 6063 Alloys

Abstract In this study, the effect of aging heat treatment on the hardness of AA 2024 and AA 6063 aluminum alloys was investigated by experimental and an Artificial Neural Network (ANN). AA 2024 and AA 6063 aluminum alloys were solution treated at two different temperatures of 490° C and 520° C. Then both samples were cooled to room temperature. After this process, the samples were aged at three different temperatures (140° C, 180° C, 220° C) for ten different periods of time (2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 h.). The experimental results were trained in an ANNs program, and the results were compared with experimental values. It is observed that the experimental results coincided with the ANNs results.

Effect of Mill Type on Morphology of AA6013 Aluminium Powder

In conventional recycling method, metal chips are cast after pressing and melting in electric arc furnace. Material loss occurs during the recycling from liquid metal due to the several reasons. Direct recycling method which produces the aluminium powder from aluminium chips using mechanical mill can be an alternative to conventional recycling method. Thus material and energy losses, and labour cost will be reduced by direct recycling method without melting. In this study, the particle morphology of powder direct recycled from AA6013 aluminium alloy chips with cryogenic, disc and ball type grinders is investigated. Mechanical milling resulted flaky and irregular shaped AA6013 particles. It was ascertained that the chips did not break sufficiently in despite of the long duration milling mechanisms by ball mill. Cryogenic mill provides the energy required for milling mechanisms to act. Disc mill has the highest impact energy was determined. Consequently, efficiency of ball mill is lower than the efficiency of cryogenic and disc type mills. Shape factors of powders produced with ball and cryogenic mills were found greater than that of the powder produced by disc mill. Disc mill has the most efficient and effective impact energy which produces the smaller particles per minute, was determined.

Cold metal transfer welding of AA1050 aluminum thin sheets

This study was aimed to investigate the welding parameters on mechanical behavior of 2 mm thick AA1050 sheet materials joined by cold metal transfer (CMT) method. Macro structural examination showed that decreasing heat input decreased the pore size in the weld metal. Tensile test was applied and failure occurred in heat affected zone of aluminum sheet metal. Maximum tensile strength was found in the sample with minimum heat input. Heat affected zone was observed explicitly in the sample produced with the maximum heat input. Decreasing joint gap affected the bending strength positively. Bending strength was found superior with maximum bonding line length.

Mechanical Properties of Dissimilar and Similar Cold Metal Transfer Welded Galvanized Steel 1314 and Aluminum AA1050

Abstract This study aims to investigate the weldability of 1050 aluminum alloy (AA1050) and galvanized 1314 steel by the cold metal transfer (CMT) procedur, comparing it with respective welding of similar aluminum sheets. Mechanical properties of welded specimens were determined by tensile testing and hardness measurements. The study was completed by microstructural analysis. The results showed that CMT welding can be applied successfully to join aluminum and steel.

The Effect of the Retrogression Process on the Wear Behaviour of a 7075 Aluminium Alloy

Abstract Retrogression and re-aging (RRA) process are applied in an attempt to enhance mechanical properties and corrosion resistance of 7075 aluminium alloys. In this study, retrogression and re-aging process have been applied to a 7075 aluminium alloy at 170°C for 5, 40, 80 min and wear resistance of RRA applied samples have been investigated by ball-on-disc wear test apparatus. Sliding distance has been chosen as 300 meters. Re-aging procedure has been carried out at 125°C for 10, 20 and 30 hours. Minimum wear loss has been obtained by retrogression for 40 min and aging for 30 hours.

Investigation of the Influence of the Pre-Aging Process on the Hardness of 6082 and 7075 Aluminum Alloys

Abstract In this study, the effect of pre-aging time and temperature on mechanical properties of aluminium alloys 6082 and 7075 has been investigated. Pre-aging has been applied at 50, 60, 70 and 80 °C for 24, 72, 144 hours after solution treatment process at 560 °C for 1 hour. Then these samples have been subjected to an aging process at 180 °C and 125 °C. The hardness of samples has been measured during aging process regularly. Eventually, it was determined that if pre-aging process is performed at low temperature, an increase of hardness occurs and hardness decreases with increasing temperature during aging.

Determination of tribological properties at CuSn10 alloy journal bearings by experimental and means of artificial neural networks method

Purpose – It is important to know the friction coefficient and wear loss for determination of tribological conditions at journal bearings. Tribological events that influence wear and its variations affect experimental results. The purpose of this paper is to determine friction coefficient and wear loss at CuSn10 alloy radial bearings by a new approach. In experiments, effects of bearings have been examined at dry and lubricated conditions and at different loads and velocities.Design/methodology/approach – In this study, friction coefficient and wear losses of journal and bearing have been determined by a new approach with a radial journal bearing test rig and artificial neural networks (ANNs) method. The ANN typifies a learning technique that enables the hidden input‐output relationship to be mapped accurately. Bronze‐based materials have been used as bearing material. Effects of friction coefficient and wear losses have been examined at same load and velocity and at dry and lubricated conditions.Findings...