Papers by Keyword: High Strength Aluminium Alloy

Abstract: The usage of modern high strength aluminium alloys are getting more remarkable in several industry sectors mostly the fabrication of light weight structures, such as vehicles, railway transport systems, aerostructures and building constructions. The weldability problems of these alloys are more complex than the steels with similar strength. Therefore weldability problems must be analyzed very accurately, by the help of the modern physical simulation. By knowing the difficulties of the weldability of high strength aluminium alloys the proper parameters of the welding technology can be defined. This article represents the investigation of a certain weldability problem of 6082T6 aluminium alloy with the aim of physical simulation and welding experiments with gas metal arc welding and pulsed current technology.

Abstract: The response of microstructure in high strength Al-Zn-Mg-Cu aluminum alloy 7055 to Graff Sargent etchant was investigated. It was found that grain boundaries and subgrain boundaries were easily corroded due to presence of η phase, and grain boundaries were corroded more rapidly than subgrain boundaries. The grain structure could be revealed quite clearly after immersion for about 15s. S (Al₂CuMg) and Al₇Cu₂Fe phase were quite stable during immersion if the time was not very long. A dealloying for Al/Mg in the S and Al₇Cu₂Fe phase was found after long time immersion. Prolonged immersion resulted in serious corrosion of subgrain boundaries, consequently separation of fine subgrains.

Abstract: Aluminium AA7075 is well known as extrusions, plate or sheet metal predominately in aerospace applications. The continuing efforts for reducing the weight but still maintaining the safety of vehicle structures are opening up the way for this alloy in automotive applications. Since this branch is very different to space as well as aircraft industries in manufacturing methods, costs and production numbers, the development of appropriate processes is necessary. After showing a high potential for deep drawing of AA7075 sheets under elevated temperatures, the joining technology options are now under investigation too. Since spot welding is very common in automotive body-in-white manufacturing, an innovative version of this process is evaluated for applicability for welding AA7075-T6 sheets to each other and to proven automotive aluminium alloys. The results of sample weldments, including mechanical static strength, micrographs, hardness, radiography and parameters for a stable process range, are presented.

Abstract: The table of L9 (34) of orthogonal design was adopted in the experiment. The optimal formulation and process conditions of electroless nickel plating on high strength aluminum alloy were determined. The influences of bath composition and operating conditions on the hardness and deposition rate were analyzed and discussed. The experimental results show that the optimal plating formulation were obtained, which were consisted of nickel sulfate hexahydrate(25g/L), sodium hypophosphite(20g/L) and sodium acetate(15g/L). The operating conditions are as follows: 80~85°C, pH value 5.0. The coating structure is more homogenous and compact, and the coating has good brightness. Meanwhile, the hardness is up to 376.8HV, and the deposition rate is 17.2μm/h. The order of effects on hardness is pH value, sodium acetate, sodium hypophosphite and nickel sulfate concentration in turn. The hardness of coating decreased after heat treatment on low temperature. When the temperature exceed 200°C, the hardness increased with temperature rising and reached the peak value at 400°C(565.3HV).

Abstract: Fatigue limit for surface crack initiation on shot peened Aluminium Alloys resulted to be determined by surface residual stress and stress concentration, according to the magnitude of the applied stress. The effect of surface roughness considered as micro-notches (dents) has been analysed by using the Vallellano and Navarro’s formulation. It was also determined that the stress gradient associated to those dents dominates over the closure stress effect.

Abstract: This paper describes a theoretical and experimental analysis on full-filed stress distribution from thermoelastic measurements and its application to determination of stress concentration. The sum of the principal stress can be measured by Thermal Stress Analysis (TSA). Lock-in Thermography has been applied to measure the sum of principal stress distribution of component structure by its high thermal resolving. In this study, Finite element method is used to calculate the sum of principal stress distribution, and the thermoelastic effect model is developed to study the relationship between the temperature deviation and the applied stress in an elastic material. Experiments were carried out with ANSI 7071 high strength aluminum alloys ply and ones with a crack under cyclic load. The thermoelastic constant is obtained for ANSI 7071 high strength aluminum alloys materials. The stress concentration factor is calculated for a ply with modeling crack under the condition of different loads. The experiment was carried out with high strength aluminum alloys component structure with rivet joints. The experimental results show the stress distribution can be measured and analyzed the contact stress distribution between ply and rivet by using Lock-in thermography. It was found that the structure stress can be evaluated with good accuracies by the lock in thermography.

Abstract: This paper deals with a definition of a relatively novel technique to improve the fatigue behavior of high strength aluminum alloys, namely, Fluidized Bed Peening (FBP). Fatigue samples made from AA 6082 T6 alloy were chosen according to ASTM regulation about rotating bending fatigue test and, subsequently, treated by varying FBP operational parameters and fatigue testing conditions. First, a full factorial experimental plan was performed to assess the trend of number of cycles to rupture of fatigue samples varying among several experimental levels the factors peening time and maximum amplitude of alternating stress applied to fatigue samples during rotating bending fatigue tests. Second, design of experiment (DOE) technique was used to analyze the influence of FBP operational parameters on fatigue life of AA 6082 T6 alloy. Finally, ruptures of FB treated samples and untreated samples were discussed in order to evaluate the influence of operational parameters on the effectiveness of FBP process and to understand the leading process mechanisms. At any rate, the fatigue behavior of processed components was found to be significantly improved, thereby proving the suitability of FBP process as alternative mechanical technique to enhance fatigue life of components made from high strength aluminum alloy.

Abstract: Aluminum-based alloys containing quasicrystalline particles of 50 – 600 nm in diameter as a reinforcing phase were produced in the form of powder or ribbons by water atomization or melt spinning techniques, respectively. Rods were compacted from powders and some ribbons by severe plastic deformation without sintering. Structure and mechanical behavior of alloys are discussed.