Transformation of Metastable β-Solid Solution in Alloy VTI-4

Abstract

Phase transformations in aging of alloy VTI-4 quenched from the b-domain are studied in the temperature range of 550 -750°C. Two morphological types of precipitates of an orthorhombic O-phase are detected. A scheme of evolution of the transformations is suggested. Variation of the lattice constants of the b-and O-phases and of the hardness in the aging process is plotted.

Thermal Analysis of the Mechanism and Kinetics Parameters of the Metastable Phases Precipitation in the Al-Mg-Si Alloy

“…The formation of precipitation during the heat treatment plays a crucial role on the final properties of Al-Mg-Si alloys like strength, machinability, corrosion resistance and electrical conductivity. They are not only determined by the formation of a specific phase, but are also related to the structural characteristics of the phase, such as the morphology, size distribution and density number [7,8].The structural hardening phenomenon and the precipitation sequence of this alloy have been vastly investigated using differential scanning calorimetry (DSC) [9][10][11][12]. In general, the accepted precipitation sequence during aging treatment is as follows [13][14][15][16][17][18][19]: α (SSS) → Mg/Si atomic clusters → GP Zones → β" → β' → β Where α (SSS) is the supersaturated solid solution, GP zones represent the Guinier-Preston zones, β'' the metastable precipitates with a needle-like shape, β' the metastable precipitates with a rod-like shape (or lath-like shape) and β the equilibrium phase with a plate-like shape [16].…”