Karakterizacija varjenja s trenjem in mešanjem različnih aluminijevih zlitin

Škof, Luka (author), Klobčar, Damjan (mentor), Trdan, Uroš (comentor)

V letalski industriji se kaže stalen trend po uporabi delov, izdelanih s kombinacijo različnih materialov. To izhaja iz zahteve redukcije stroškov izdelave, manjše mase letal ter koriščenja različnih mehanskih lastnosti na posameznem segmentu letala. Uporaba varjenja s trenjem in mešanjem se je izkazala za učinkovit nadomestek kovičenim spojem. Konstrukcijski deli, izdelani s tem postopkom, ob izbiri ustreznih varilnih parametrov, dosegajo kakovostnejši spoj od kovičenega, izdelava spoja pa je preprosta. Enega izmed glavnih problemov takšnih spojev pa še vedno predstavlja heterogena mikrostruktura s številnimi fazami, natezne zaostale napetosti, povečana hrapavost in nihanja trdote v zvarnem spoju. V diplomskem delu smo analizirali učinke varjenja s trenjem in mešanjem spojev izdelanih iz raznorodnih visoko-trdnostnih aluminijevih zlitin 2017A-T451 in 7075-T651. V prvi fazi smo ovrednotili longitudinalne zaostale napetosti po dolžini zvarnega spoja, nato izmerili mikrotrdoto ter analizirali hrapavost in valovitost. V zadnjem delu smo opravili še stereološke analize v različnih mikrostrukturnih področjih. Rezultati so potrdili splošen trend povečevanja napetosti proti sredini spoja ter povečano hrapavost in valovitost na prehodu osnovni material/spoj. V sredini zvarnega spoja smo potrdili zmanjšanje mikro-trdote z izrazito izotropno in drobnozrnato strukturo na nivoju ~ 4 μm zaradi učinka dinamične rekristalizacije.

• Language: Slovenian
• Keywords: raznorodne visoko-trdnostne aluminijeve zlitine, varjenje s trenjem in mešanjem - FSW, zaostale napetosti, rentgenska difrakcija, mikrostruktura, mikrotrdota
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [L. Škof]
• Year: 2019
• Number of pages: XXII, 56 str.
• PID: 20.500.12556/RUL-107679
• UDC: 621.791:669.715(043.2)
• COBISS.SI-ID: 16632091
• Publication date in RUL: 12.05.2019

ŠKOF, Luka, 2019, Karakterizacija varjenja s trenjem in mešanjem različnih aluminijevih zlitin [online]. Bachelor’s thesis. Ljubljana : L. Škof] . [Accessed 26 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=107679

Secondary language

• Language: English
• Title: Characterization of friction stir welding of dissimilar aluminium alloys

Abstract

In the aviation industry, there is a constant need for the parts made with a combination of various materials. This follows from the requirement of reducing production costs, reducing the mass of aircraft and using different mechanical properties in each segment of the airplane. Friction stir welding process has proven to be an effective substitute for riveted joints. The construction parts produced by this process, when selecting the appropriate welding parameters, achieves improved mechanical properties than with rivets, and the construction of the joint is simple. However, one of the main problems of such joints is a heterogeneous microstructure with many phases, tensile residual stresses, increased roughness and fluctuation of hardness in the welding joint. In the thesis we analyzed the effects of friction stir welded joints made from dissimilar high-strength aluminum alloys 2017A-T451 and 7075-T651. In the first phase we evaluated longitudinal residual stresses along the length of the welded joint, then measured the microhardness and analyzed roughness and waviness. In the last part, we have also performed stereological analysis in various microstructural areas. The results confirmed the general trend of increasing the tensile residual stresses towards the center of the joint and the increased roughness and waviness at the transition of the base material/joint. In the middle of the welding joint, we confirmed a decrease in the micro-hardness with an extremely isotropic and fine-grained structure in the range of ~ 4 μm due to the effect of dynamic recrystallization.

• Keywords: dissimilar high-strength aluminium alloys, friction stir welding - FSW, residual stresses, x-ray diffraction, microstructure, microhardness