Controlling Thermo-Mechanical Properties of Warm Rolled Commercial Al-Cu-Mg Alloy by Addition of Second Phase Particles

Abstract

Al-Cu-Mg (V65) alloy is widely used for making rivet as is significantly shows slower natural aging response, which gives flexibility to carryout riveting operation even after four days after solution heat treatment and natural aging at room temperature. In Aluminium alloys a fine-grained structure shows better strength than coarse grained alloy as the former has a greater total grain boundary area to stop the dislocation motion. These features can be controlled by thermo mechanical processing of the material which may be carried in cold or hot conditions with intermediate anneals. Controlling Thermo Mechanical Properties of this alloy has extensively been discussed. One of the successful methods in this regard is the addition of second phase particles which exert a Zener drag by controlling the curvature of the grains and thereby inducing fine grain sizes. In the present work Zirconium was added to the alloy in the form of second phase particles. Addition of Zirconium to commercial Al-Cu-Mg alloy (V-65) alloy has pronounced effect in forming bimodal distribution of Al3Zr particles. The fine particles produce fine grain structure and coarse particles stimulate nucleation of recrystallization by a mechanism called Particle Stimulated Nucleation. In the present work the alloys were subjected to differential thermal analysis (D.T.A) and peaks were observed at around 420°C, indicating the dissolution of Al3Zr particles. The alloy was warm rolled at 300 & 350°C and the kinetics of Recrystallization was followed by image analysis on samples of recrystallized at 420°C for various times assuming that short duration of anneal would not dissolve Al3Zr because of diffusion coefficient of Zirconium in Aluminium is low. Transmission Electron Microscopy was also conducted and the fine particles were found to be Al3Zr particles with L1-2 crystal structure and lattice parameter 4.08 A0.The volume fractions of recrystallized grains were measured which showed considerable reduction indicating the fine grained structure in the final product