Abnormalni rast zrna u toku medjužarenja u Al-Mg legurama

Abstract

U završnoj fazi prerade Al-Mg legura, pojava abnormalnih zrna (AGG) u strukturi je nepoželjna, jer dovodi do pogoršanja mehaničkih osobina. Medjutim, postoji veliki interes za proučavanjem uticaja AGG, koja nastaju u toku medjužarenja, na razvoj mikrostrukture i teksture tokom dalje prerade. Naime, odredjene teksturne komponente i tipovi granica zrna imaju pozitivan uticaj na deformaciono i koroziono ponašanje.U ovom radu je opisan efekat uslova medjužarenja i hemijskog sastava na mikrostrukturu Al-Mg legura. Uzorci, izohrono žareni na temperaturama 350-550°C,ili tretirani na 520°C pri različitim vremenima, su ispitivani optičkom mikroskopijom u polarizovanom svetlu. Utvrdjeno je da je AGG ograničen na pojas u blizini ivice uzorka. Abnormalna zrna poseduju visok stepen anizotropije, a inicijalno brz rast stagnira sa produžetkom žarenja. Uticaj hemijskog sastava na pojavu AGG je ispitivan u slučaju četiri legure i rezultati su pokazali da niži sadržaj legirajućih elemenata pospešuje AGG.

During final annealing of Al-Mg alloys, abnormal grain growth (AGG) is undesirableasit deteriorates mechanical properties. However, there is interest to investigate how the introduction of the AGG during intermediate annealing affects microstructure and texture development upon further processing.It is known that certain texture components and grain boundary types can affect formabilityand IGC susceptibility. In this study, the effect of intermediate annealing conditions andchemical composition on the microstructure of of Al-Mg alloysis reported. The specimens,annealed isochronally at temperatures of 350- 550°C or isothermally at 520°C for various times, were examined by optical microscopy in polarized light. It is found that the AGG is confined to a band near the surface.There is astrong anisotropy in grains shape and initially rapid grain growth stagnates with furtherannealing. The influence of the chemical composition on the AGG was investigated in four alloys and the results showed that the decrease in the alloying elementscontent promoted AGG.