EFFECT OF THE HEAT AND SURFACE LASER TREATMENT ON THE CORROSION DEGRADATION OF THE Mg-Al ALLOYS

In this paper there is presented the corrosion behavior of the cast magnesium alloys as cast state, after heat and laser treatment. Pitting corrosion resistance of the analyzed alloys was carried out using the potentiodynamic electrochemical method (direct current), based on a anodic polarization curve. On the basis of the achieved anodic polarization curves, using the Tefel extrapolation method near to the corrosion potential, the quantitative data were determined, which describe the electrochemical corrosion process of the investigated alloys: value of the corrosion potential Ecorr (mV), polarization resistance RP (kohm.cm2), corrosion current density icorr (10-6A/cm2), corrosion rate Vcorr (mm/year) as well the mass loss Vc (g/m2<)

Površinska obrada laserom Mg-Al-Zn legura

In this paper the structure and properties investigations results of the cast magnesium alloys in the as cast state, after heat treatment and laser surface treatment are presented. The aim of this work was to improve the surface layer properties of the Mg-Al-Zn cast magnesium alloys by melting and feeding of TiC, VC, WC, SiC, NbC and Al2O3 particles onto the surface. Laser processing was carried out using high diode power laser (HDPL). A series of experiments was carried out with varying scan rates and laser power. The resulting surface layers were examined using metallographic optical microscopy, scanning electron microscopy, X-ray diffraction, microhardness measurements and corrosion resistance tests. Mg-Al-Zn alloys after laser treatment are characterized by two zones: alloyed zone (AZ) and heat affected zone (HAZ) with different thickness and shape depending on laser power and ceramic powder used. Alloyed zone is composed mostly of dendrites with the Mg17Al12 lamellar eutectic and Mg in the interdendritic areas. The increase of microhardness from about 50 HV0,1 to about 200 HV0,1 in alloyed zone were observed.U ovom radu prezentirana je struktura i mehanička svojstva ljevačke magnezijske legure u ljevačkom stanju, nakon toplinske obrade i obrade površine laserom. Cilj ovog rada je unaprijediti svojstva površinskog sloja Mg-Al-Zn ljevačke magnezijske legure taljenjem i dodavanjem čestica TiC, VC, WC, SiC, NbC i Al2O3 na površinu. Obrada laserom izvodila se laserom visoke snage na diodi (HDPL). Serija eksperimenata izvodila se varirajući brzinu skeniranja i snagu lasera. Rezultirajući sloj na površini ispitivalo se metalografskim svjetlosnim mikroskopom, scanning elektronskim mikroskopom, difrakcijom x-zrakama, mjerenjem tvrdoće i mikrotvrdoće i testovima korozijske otpornosti. Poboljšanje proizvodne tehnike i kemijskog sastava kao i metoda toplinske obrade dovode do razvoja projektiranja materijala za optimalna fizikalna i mehanička svojstva novorazvijenih legura