Obtención de una microestructura nueva en la aleación Zn - 40%at. Al - 1. 5%at. Cu

Abstract

In a previous investigation, some acicular particles were found in the microstructure of Zn - 40 %at. Al - 1.5 %at. Cu alloy, when it is maintained at 376$^\circ$C and later cooled in the furnace. The aims of the present work are to establish the optimal treatment time to obtaining a microstructure with such micro - constituent in a high quantity and uniformly distributed, to realize relative mechanical basic characterization and by X - rays diffraction during its formation, and EDS microanalysis in integrants of the microstructure finally obtained in Zn - 40%at. Al - 1.5%at. Cu alloy. A plate of this alloy in as - cast condition was rolled in several steps for eliminate more easily its structure with heat treatments applied later. Little sheets of this alloy were maintained different times at 359, 376 and 380$^\circ$C, and they were cooled off later in the furnace. The microstructures produced were analysed and photographed, and their Rockwell 15T hardness and Vickers micro-hardnesses in their components settled down. It was established that wished microstructure is obtained with the thermal treatment by 50 hours at 376$^\circ$C. It is a new microstructure because one of its component, the acicular integrant, has a distribution, size, form, quantity and type that are different to those of any integrant of microstuctures of alloy treated different times at 359 and 380$^\circ$C. The acicular integrant increases the hardness of most components imbibed it, and it is the high - temperature $\beta$ phase. The treatment at 376$^\circ$C diminishes the relative softening that is normally caused by the increase of treatment time at constant temperature in metals previously rolled, and produce an alloy that is slightly more hard.