Al-6061 Alaşımı İçin Uygun Elektrokimyasal İşleme Parametrelerinin Ve Elektrolitin Araştırılması
Korkmaz, Gülnur Şehnaz
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For conductive materials with high hardness and heat resistance or in thin film form, which are difficult to machine accurately by conventional methods, electrochemical machining (ECM) is used as an advanced manufacturing method. In this method, machining is accomplished by ionization of the atoms at the surface of the work piece by applying an electric potential in a liquid electrolyte. With technological developments, high quality materials that have low surface roughness enough to be processed via ECM method in micro dimensions with precision are needed in defense, aviation and medical industries. There are various studies that study processing of high hardness materials such as titanium, nickel and carbide via ECM method. Aluminum alloys have lower surface hardness compared to other materials. Thus, they can be processed with traditional methods; however complicated shapes which are demanded in advanced technology industries need to be processed more delicately. In the study, with this reason, electrochemical method processing potential of A1-6061 alloy which is used considerably in our country is researched in a local ECM bench which was developed under the scope of TR Industry and Commerce Ministry, Techno Initiative Fund Support program and suitable work parameters are determined. Main purpose of this study is to determine the electrolyte that has suitable chemical contents, concentration and pH value in order to obstruct passivization on the surface of workpiece, and to obtain high material removal rate (MRR) and minimum surface roughness. Conductivity of solutions of NaBr, NaCl, NaNO3 and NaF salts were determined in different concentrations whilst they were processed. Design Expert, which is a statistical software was used in the experimental design. 1,370 M NaBr ve 0,755M NaBr-0,036 M NaNO3-1,726 M NaCl solutions are determined as electrolytes to provide best MRR and surface quality. Determined solutions were used with 1 M NaOH, 0,1 M HNO3 and 0,1 M HCl solutions in order to observe acidic and alkaline environment effect on material processing performance and pH value was changed as 2 and 10. It was observed that acidic work environment has better effect on surface quality. It has been determined that, using HCl with these two electrolytes of pH value 2 is the best solution for this study. After determining the best electrolyte solutions, study was done by changing the working conditions of the ECM device. In scope of parameter study, machining time as 5 and 15 minutes, inter electrode gap as 1, 2 and 3 mm, voltage value as 5 and 8 V were applied. Results which were obtained from parameter study was analyzed with statistical analysis program. Working conditions were determined as pH 2/ 0,660 M NaBr-0,061 M NaNO3- 1,729 M NaCl as electrolyte, 15 min as machining time, inter electrode gap as 2 mm and voltage value as 8 V. As a result, for Al-6061 alloy, best MRR and materials with best surface quality was obtained in determined conditions. Results obtained in this thesis has a tremendous usage potential in industrial field and will make important contributions to country's industry and technology.