M. H. Goodarzy, H. Arabi, M. A. Boutorabi, S. H. Seyedein, H. Shahrokhi,
Volume 11, Issue 1 (3-2014)
Abstract
Variation in microstructural features of 2024 aluminum alloy plastically deformed by equal channel angular pressing (ECAP) at room temperature, was investigated by X-Ray diffraction in this work. These include dislocation density dislocation characteristic and the cell size of crystalline domains. Dislocations contrast factor was calculated using elastic constants of the alloy such as C 11, C 22 and C 44 . The effect of dislocations contrast factor on the anisotropic strain broadening of diffraction profiles was considered for measuring the microstructural features on the base of the modified Williamson-Hall and Warren-Averbach methods. Results showed that the dislocations density of the solution annealed sample increased from 4.28×10 12m-2 to 2.41×10 14m-2 after one pass of cold ECAP and the fraction of edge dislocations in the solution annealed sample increased from 43% to 74% after deformation. This means that deformation changed the overall dislocations characteristic more to edge dislocations. Also the crystalline cell size of the solution annealed sample decreased from 0.83μm to about 210nm after one pass of ECAP process at room temperature
N. Khatami , Sh. Mirdamadi,
Volume 11, Issue 1 (3-2014)
Abstract
The presence of alloying elements, sometimes in a very small amount, affects mechanical properties one of these elements is Boron. In Aluminum industries, Boron master alloy is widely used as a grain refiner In this research, the production process of Aluminum –Boron master alloy was studied at first then, it was concurrently added to 2024 Aluminum alloy. After rolling and homogenizing the resulting alloy, the optimal temperature and time of aging were determined during the precipitation hardening heat treatment by controlled quenching (T6C). Then, in order to find the effect of controlled quenching, different cycles of heat treatment including precipitation heat treatment by controlled quenching (T6C) and conventional quenching (T6) were applied on the alloy at the aging temperature of 110°C. Mechanical properties of the resulting alloy were evaluated after aging at optimum temperature of 110°C by performing mechanical tests including hardness and tensile tests. The results of hardness test showed that applying the controlled quenching instead of conventional quenching in precipitation heat treatment caused reduction in the time of reaching the maximum hardness and also increase in hardness rate due to the generated thermo-elastic stresses rather than hydrostatic stresses and increased atomic diffusion coefficient as well. Tensile test results demonstrated that, due to the presence of boride particles in the microstructure of the present alloy, the ultimate tensile strength in the specimens containing Boron additive increased by 3.40% in comparison with the specimens without such an additive and elongation (percentage of relative length increase) which approximately increased by 38.80% due to the role of Boron in the increase of alloy ductility
