Modifikacija površine magnezijeve zlitine AZ80 s postopkom laserskega udarnega utrjevanja

magistrsko delo magistrskega študijskega programa II. stopnje Strojništvo

Peter Kranjc Požar (Author), Sebastjan Žagar (Mentor), Roman Šturm (Co-mentor)

Abstract

Magnezij ima zaradi edinstvenih mehanskih lastnosti in razpoložljivosti v naravi zelo velik potencial za inženirske aplikacije. Poleg tega lahko z legiranjem doseže še mnogo izboljšane lastnosti. Pri magnezijevih zlitinah so to njihova nizka gostota, razmerje med težo in trdnostjo ter dobra obdelovalnost. Zlitina AZ80 je v inženirskih aplikacijah pogosto uporabljen material, katerega glavni legirni elementi so aluminij, mangan ter cink in je predmet raziskovanja te naloge. Bila je topilno žarjena (420 °C za 24 h), vzorci za preiskavo so bili narezani kolobarji vlečene palice. Vsi štirje vzorci so bili obdelani z laserskih udarnim utrjevanjem, dva od vzorcev pa sta bila tudi predhodno toplotno obdelana z izločevalnim utrjevanjem (8 h pri 250 °C). Pogoji laserske obdelave so bili enaki z razliko v gostoti pulzov (178 in 400 pulzov/cm2). Analiza je obsegala preiskavo mikrostrukture, topografije, hrapavosti, mikrotrdote, zaostalih napetosti ter korozijske odpornosti ter primerjavo z osnovnim materialom. Hrapavost je bila zaradi laserske obdelave povečana, v zgornjem sloju površine so bila kristalna zrna udrobnjena, sorazmerno s tem pa tudi višja mikrotrdota ter tlačne zaostale napetosti. Izločevalno utrjevanje je imelo na korozijo precejšen vpliv, saj ti vzorci v nasprotju z vzorci v osnovnem stanju s časom niso kazali zmanjšanja korozijskega potenciala, prav tako je bila hitrost korozije mnogo manjša, repasivacija materiala pa boljša. Nasprotno pa je bila stabilnost površinskega filma nekoliko zmanjšana.

Keywords

magistrske naloge;magnezijeva zlitina AZ80;lasersko udarno utrjevanje;mikrostruktura;mikrotrdota;korozijska odpornost;hrapavost;topografija;zaostale napetosti;

Data

Language:	Slovenian
Year of publishing:	2024
Typology:	2.09 - Master's Thesis
Organization:	UL FS - Faculty of Mechanical Engineering
Publisher:	[P. Kranjc Požar]
UDC:	669.721.5:620.173.2:544.537(043.2)
COBISS:	196746243
Views:	33
Downloads:	16
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Surface modification of magnesium alloy AZ80 with laser shock peening
Secondary abstract:	Magnesium, due to its unique mechanical properties and natural availability, holds significant potential for engineering applications. Furthermore, through alloying, its properties can be further enhanced. In magnesium alloys, these include low density, a favorable weight-to-strength ratio, and good machinability. The AZ80 alloy is a commonly used material in engineering applications, with its main alloying elements being aluminum, manganese, and zinc, which is the subject of investigation in this task. It was solution heattreated (at 420°C for 24 hours), and samples for examination were cut from drawn rod billets. All four samples underwent laser shock peening, with two of them also subjected to prior precipitation hardening (8 hours at 250°C). The laser processing conditions were identical except for differences in pulse density (178 and 400 pulses/cm²). The analysis included an examination of microstructure, topography, roughness, microhardness, residual stresses, corrosion resistance, and a comparison with the base material. Surface roughness increased due to laser processing, with grain refinement observed in the upper surface layer, along with higher microhardness and compressive residual stresses. Precipitation hardening had a significant effect on corrosion, as these samples, unlike those in the base condition, did not show a decrease in corrosion potential over time. Moreover, the corrosion rate was much lower, and material repassivation was improved. However, the stability of the surface film was somewhat reduced.
Secondary keywords:	master thesis;magnesium alloy AZ80;laser impact hardening;microstructure;microhardness;corrosion resistance;surface roughness;topography;residual stresses;
Type (COBISS):	Master's thesis/paper
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. Ljubljana, Fak. za strojništvo
Pages:	XX, 81 str.
ID:	23799422