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ABSTRACT: Friction stir processing is a process for processing metallic materials that aims to locally modify the microstructure and mechanical properties. Submerged friction stir processing aims to limit the process temperature by using a liquid working medium, so as to avoid thermal overloading of the processing tool and the materials to be processed. The paper presents experimental research carried out at ISIM Timisoara on submerged friction stir processing for the 5mm thick EN AW 7075 aluminum alloy. Processing experiments were carried out in single pass and in multiple passes, with positive results. The evaluation program of samples/test pieces taken from the processed materials included visual examination and penetrating radiation, macroand microscopic structural analyses, as well as mechanical tensile and bending tests.
KEYWORDS: submerged friction stir processing SFSP, EN AW 7075 aluminum alloy, single and multiple passes, structural analysis, mechanical properties.
1. INTRODUCTION
Friction stir processing is an ecological, modern and versatile method of processing metallic materials. It is an area of interest for scientific research, as well as for specialists from leading industries, in order to know the process and its particularities, to analyze the possibilities and limits of application to a wide range of metallic materials and of specific applications [1-14].
Derived from friction stir welding (FSW), friction stir processing (FSP) has the same process principle and uses the same working equipment. The difference is that the process does not join materials, but is applied only to a material with the aim of locally modifying its microstructure and mechanical properties on limited areas.
In both FSW welding and FSP processing, the process takes place in the solid-state, below the melting temperature of the processing materials [5], [7-9], [13, 15, 16]. The processing tool is positioned along the processing line, rotates around its axis at a preset speed, the tool pin penetrates the material to be processed until firm contact is made between the tool shoulder and the upper surface of the material to be processed, at which point the tool begins to move along the processing line at the set processing speed.
The tool speed, processing speed, number of processing passes and the working medium are factors that influence the amount of heat released in the process and the plasticization of the material...