Showing 5 results for Aluminum Alloys
M. Goodarzi, S. M. A. Boutorabi, M. A. Safarkhanian,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract:In this study, an effort has been made to determine the influence of rotational speed of tool on themicrostructure and hardness values of friction stir welded 2024-T851 aluminum alloy. The microstructure of stir zonein the joints has been investigated. It was found that the particles such as Al6(CuFeMn) particles are broken up duringfriction stir welding, and the degree of break up of these particles in the stir zone increases with increasing rotationalspeed. Since the break up of these particles and the recrystallization of new grains happen simultaneously, the brokenparticles would be placed in the grain boundaries. Moreover, the hardness value in the stir zone increases withincreasing rotational speed
A. Davoodi, J. Pan,ch. Leygraf, Gh. R. Ebrahimi, M. Javidani,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract: Localized corrosion of aluminum alloys is often triggered by intermetallic particles, IMP’s. To understandthe role of IMP’s in corrosion initiation of EN AW-3003, efforts were made to combine nano-scale ex-situ analysis ofthe IMP’s by SEM-EDS, SKPFM and in-situ AFM monitoring of the localized attack in chloride containing solution.The results showed that two distinct types of eutectically-formed constituent IMP’s exist the -Al(Mn,Fe)Si and theAl(Mn,Fe) phases. However, the exact chemical composition of the IMP’s varies with the particles size. Volta potentialdifference of surface constituents revealed that IMP’s have a higher Volta potential compared to the matrix, indicatingthe cathodic characteristic of the IMP’s. Noticeably, the boundary regions between the matrix and IMP’s exhibited aminimum Volta potential probably the sites for corrosion initiation. Localized corrosion attack monitored by in-situAFM clearly showed the trench formation occurrence around the large elongated IMP’s in the rolling direction.
A. Jafaria, S. H. Seyedeina, M. R. Aboutalebia, D. G. Eskinb, L. Katgermanb,
Volume 7, Issue 3 (8-2010)
Abstract
ABSTRACT Macrosegregation has been received high attention in the solidification modeling studies. In the present work, a numerical model was developed to predict the macrosegregation during the DC Casting of an Al-4.5wt%Cu billet. The mathematical model developed in this study consists of mass, momentum, energy and species conservation equations for a two-phase mixture of liquid and solid in an axisymmetric coordinates. The solution methodology is based on a standard Finite Volume Method. A new scheme called Semi-Implicit Method for Thermodynamically-Linked Equations (SIMTLE) was employed to link energy and species equations with phase diagram of the alloying system. The model was tested by experimental data extracted from an industrial scale DC caster and a relatively good agreement was obtained. It was concluded that a proper macrosegregation model needs two key features: a precise flow description in the two-phase regions and a capable efficient numerical scheme
M. Fallah Tafti, M. Sedighi, R. Hashemi,
Volume 15, Issue 4 (12-2018)
Abstract
In this study, the microstructural variations, mechanical properties and forming limit diagrams (FLD) of Al 2024 aluminum alloy sheet with the thickness of 0.81mm are investigated during natural ageing (T4) treatment. The most formability in Al 2024 can be achieved just after solution treatment, and it is better to perform the forming process, on this aluminum alloy sheet, in this condition. However, in industrial applications, there is usually a postponement for some hours after solution treatment to begin the forming process that it means the forming process should be done at the natural ageing condition. This condition decreases the formability of Al 2024 sheets. To monitor the properties variations in natural ageing condition, FLDs are determined after specific times (e.g., 0.5, 1.5, 4 and 24 hours). The variations in micro-hardness, yield strength, ultimate tensile strength and elongation at break are observed with changing the ageing time. The scanning electron microscope (SEM) investigations illustrated that density and size of precipitates are changed with ageing time. Moreover, the Nakazima test is utilized to study the forming limits considering the natural ageing condition. Results show by increasing the ageing time, up to 4hr, the majority of properties variations could be seen, and from 4hr to 24hr, the variations are changed slower.
A. Khakzadshahandashti, N. Varahram, P. Davami, M. Pirmohammadi,
Volume 16, Issue 3 (9-2019)
Abstract
The combined influence of both melt filtration and cooling rate on the microstructure features and mechanical properties of A356 cast alloy was studied. A step casting model with five different thicknesses was used to obtain different cooling rates. The effect of melt filtration was studied by using of 10 and 20 ppi ceramic foam filters in the runner. Results showed that secondary dendrite arm spacing decreased from 80 μm to 34 μm with increasing cooling rate. Use of ceramic foam filters in the runner led to the reduction of melt velocity and surface turbulence, which prevented incorporation of oxide films and air in the melt, and consequently had an overall beneficial effect on the quality of the castings. A matrix index, which is the representative of both SDAS and microporosity content, was defined to consider the simultaneous effect of melt filtration and cooling rates on UTS variations. Also, the fracture surface study of test bars cast using 10 and 20 ppi ceramic foam filters showed features associated with ductile fracture.
