Thesis /

ROMDOC-THESIS-2016-313

Studii şi cercetări privind obţinerea barelor din aliaje de aluminiu turnate, din seria 6xxx

Sterie, Rodica
2008-10-24

Abstract: In the study there are presented and interpreted the results obtained at the aluminum alloy billets casting and homogenization. There are also presented and interpreted the test results obtained at the finishing of the aluminum alloy granulation with AlTi5B1 finisher master alloy. Three types of 6xxx series alloys, namely 6000, 6063 and 6082 were studied. The alloys were industrially cast at S.C. ALRO S.A. Slatina on a WAGSTAFF casting machine. The quality of cast billets external surface was analyzed by its comparison with SAPA scale. The defects which appeared at the casting and homogenization of 6000, 6063 and 6082 alloy billets and specific measures for their elimination were analyzed. In order to determine the cast billets macrostructure, strips from their middle were cut and were metallographic prepared according to the known rules (grinding with glass paper of 320, 400 and 600 followed by fine polishing with diamond paste of 3 m and 1 m and finishing with colloidal SiO2). Determination of billets macro porosity was achieved by ZYGLO method, with penetrating fluids. On the macro porosity scale there are 7 levels. Determination of 6063 alloy billets macro porosity by ZYGLO method lead to the conclusion that the porosity level is 1 –2, thus the billets are accepted. In order to reveal the changes which take place at the 6063 billets homogenization, 3 samples were taken from 3 different positions of billets: 20 mm from the end, ¼ of the diameter and ½ of the diameter. The depth of the cortical area and of the areas situated at ¼ and ½ of diameter was determined, for the 152 mm diameter billets. On the basis of the performed microanalyses and X ray images it may be stated that at the grains limit a compound of AlMnFe type appears which dissolves a certain quantity of Si, Mg, Ca and Zr, probably Ca comes from the raw materials used for the 6082 alloy processing. It is known that a certain content of Zr can inhibit the action of granulation finishers of the Al-Ti-B system. Finishing of the 6060, 6063 and 6082 alloys granulation with a AlTi5B1 master alloy finisher was studied by examining the samples taken from various areas of billets through quantitative optical microscopy and through SEM/EDS electronic microscopy. The positive effect of titan and boron on the grain size reducing was observed, which is due to the morphology of the TiAl3 intermetallic phase as well as to the presence of complex boride (Al1-xTix)B2 in the AlTi5B1 master alloy. After finisher addition in the melt, prior to casting, the grain size reduces at 80–118 μm, and the content of alloying elements (Mg and Si) practically too little influences the structure finishing grade.

Keyword(s): Aluminiu -- Aliaje -- Teză de doctorat ; Turnare -- Tehnologie mecanică -- Teză de doctorat
OPAC: See record in BC-UPB Web OPAC
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