Strength Aluminum Alloy Research Articles

Effect of Temperature on Fatigue Transition life and Strength of Aluminum alloy

Effect of Temperature on Fatigue Transition life and Strength of Aluminum alloy

An Investigation on Strength Deterioration of Aluminum Alloy Welded Joint under Thermal Cycling Conditions

Effects of thermal cycling on the tensile strength of aluminum alloy welded joints are studied experimentally in this paper. The damage mechanisms are also analyzed based on the microstructure observations. Results reveal that certain thermal cycling can cause strength decrease especially at the heat affected zone of the aluminum alloy welded joint. The cyclic temperature and the external load are the key factors which influence the strength of the welded joint specimens, while the cyclic period has a minor effect in thermal cycling conditions. Microstructure analysis also shows that voids nucleation and evolution governs the damage process under thermal cycling condition.

Friction stir welding of precipitation strengthened aluminium alloys: scope and challenges

High strength aluminium alloys are very attractive for high structural efficiency in aerospace structures. However, the full potential of these alloys is not realised because of lower joint efficiencies. Most of the high strength aluminium alloys use precipitation strengthening as the primary strengthening mechanism. Heat flux during friction stir welding of precipitation strengthened aluminium alloys correlates with the joint efficiency. The best joint efficiency results are observed in a narrow intermediate heat flux region. The origin of this is discussed in terms of precipitate dissolution, reprecipitation and coarsening. Low intensity post-weld plastic deformation and design of dispersion containing aluminium alloys are suggested as approaches to enhance joint efficiency in friction stir welded structures.

Responses of Aging Treatment to the Behavior of Aluminum Alloy with Addition of 0.02% Zirconium Element

Response of aging treatment on aluminum alloy towards its hardness has been investigated. Alloy used on this research was develop base on a US patent 4121951 that is use to produce aluminum cable with excellent strength and conductivity [1]. Solutioninzing treatment was carried out to the alloy at 520 °C for 2 hours. Alloy then were artificial aged at 180 °C, 200 °C and 220 °C for various periods up to 10 hours. Natural aging also has been carried out for 2 weeks right after solution quenching. By referring to the results, hardness increase as the aging time increase until it reaches the maximum peak and then decreases as the result of overaging. Hardness of artificial aged alloy then was compared with 99.99% pure aluminum, as-cast and naturally aged alloy. Alloy aged at 180 °C for 2 hours give the highest value of hardness which is 34.26 Hv followed by naturally aged alloy and pure aluminum with 30.92 Hv and 15.2 Hv. The effect of different time of artificial aging gives significant change in hardness in order to improve the strength of aluminum alloy. Minor addition of zirconium during the aluminum processing will probably cause by the precipitation of Zr particles towards the aluminum matrix [2], thus increase the strength even these particulate cannot be detected by XRD. These particles will retard the grain movement and also stable upon heating due the low solubility of zirconium in aluminum matrix.

Thermal Fatigue and Fracture Mechanics Analysis of Aluminium Alloy

The in-phase and out-of-phase thermal fatigue of aluminum alloy were experimentally studied. The fatigue life was evaluated analytically by using the elastic-plastic fracture mechanics method (mainly J integral). The results of experiments and calculations showed that the life of out-of-phase fatigue was longer than that of in-phase fatigue within the same strain range. This is the same as the results of other materials such as medium and low carbon steel. On the other hand, the predicted life was consistent with experimental results. This suggests that J integral as a mechanics parameter for characterizing the thermal fatigue strength of aluminum alloy and the calculation method developed here is efficient. A parameter ΔW was proposed from energy aspect to characterize the capacity of crack propagation. The in-phase thermal fatigue life was the same as the out-of-phase thermal fatigue life for identical ΔW values.

Effect of Ultrasonic Surface Peening on Fatigue Property of 7B04 High Strength and Toughness Aluminum Alloy

This paper discusses the influence of ultrasonic surface peening on the fatigue property of 7B04 high strength and toughness aluminum alloy. The results showed that a nano-layer of 10-20 μm was formed after ultrasonic surface peening. This nano-layer had a gradient structure with grain size of 10 to 50nm. Further, the ultrasonic surface peening process created residual compressive stress of 200MPa in this nano-layer. This stress caused micro surface cracks to be compressed or closed . Consequently, after ultrasonic surface peening the fatigue life of 7B04 alloy was extended to 5 times.

On the Mutual Interactions of Monotonic and Cyclic Loading and their Effect on the Strength of Aluminium Alloys

The paper investigates the interaction of monotonic cyclic loading and their effect on the yield strength of aluminium alloy. Two different loading combinations were considered, i.e. torsion-reverse-torsion superimposed on monotonic tension and monotonic torsion combined with tension-compression cycles. All strain controlled tests were carried out at room temperature using thin-walled tubular specimens. The maximum value of the total cyclic strain amplitude was less than 1%. The influence of amplitude, frequency and shape of cyclic loading signal on the proportional limit and conventional yield point was investigated. The experimental results presented in the paper may be useful to designers of structures that utilize manufacturing processes such as drawing, extrusion, forging of selected semi-finished elements or researchers working on the development of new constitutive equations.

Fluxless laser brazing of aluminium alloy to galvanized steel using a tandem beam – dissimilar laser brazing of aluminium alloy and steels

Tandem beam brazing with aluminium filler metal (BA4047) was conducted in order to develop the fluxless laser brazing technique of aluminium alloy (AA6022) to galvanized steels (GA and GI steels). Laser powers of tandem beam and offset distance of preheating beam from the root to the steel base metal were varied. Sound braze beads could be obtained by optimizing the preheating and main beam powers under the offset distances of 0–1 mm. A small amount of zinc remained at the braze interface between galvanized steels and the braze metal. The reaction layer consisting of Fe–Al intermetallic compounds was also formed at the steel interface, and the thickness of reaction layer could be predicted during the laser brazing (thermal cycle) process based on the growth kinetics with the additivity rule. The metal flow analysis of the melted filler metal on joints revealed that wettability and spreadability of the filler metal on the GI steel joint were superior to those on the GA steel joint. The fracture strength of the lap joint attained approx. 55–75% of the base metal strength of aluminium alloy. It was concluded that fluxless laser brazing could be successfully performed by using a tandem beam because the zinc coat layer acted as the brazing flux.

Rotating extrusion technique and its effect on quality of aluminum alloy thin-plate weldments

A new technique named rotating extrusion was proposed that uses rotating extrusion action to rectify residual distortion of aluminum alloy thin-plate weldments to improve mechanical properties of welded joints. The basic principle and device of rotating extrusion were introduced. The residual distortion and stresses in rotating extrusion weldments were compared with those in conventional weldments. The differences in microstructure and mechanical properties between conventional welded joints and rotating extrusion welded joints were investigated and analyzed in order to make clear the effect of rotating extrusion on the performance of aluminum alloy weldments. Experimental results show that rotating extrusion can enhance the hardness and tensile strength of aluminum alloy welded joints evidently. This method has also potential effect on extending the life of welded structures.

Butt Joining of High Strength Steel Sheet and Dissimilar Metal Sheet by Shot Peening

In the shot peening process, the substrate undergoes large plastic deformation near the surface due to the hit with many shots. A large plastic deformation characterized by a shear droop occurs at the edge of the substrate. When the dissimilar sheets with the edge of the notch geometry are connected without level difference and then the contact area are shot-peened, the sheets can be joined due to the plastic flow generated by a large plastic deformation during shot peening. This method is similar to joining by caulking. The aim of this paper is to investigate the butt joining of high strength steel and dissimilar metal sheets using a shot peening process. The shot velocity and the coverage were controlled in the experiment. The shots used were made of high carbon cast steel and cemented carbide with an average diameter of 0.1 mm. The sheets were high strength steel and aluminum alloys. The influences of processing conditions on the joinability were mainly examined. The joint strength increased with the kinetic energy of shots. Tensile test was also examined to evaluate bond strength. It was found that the present method can be used to enhance the butt joining of high strength steel and dissimilar metal sheets.

Dent Resistance for Automobile Body Panels

Dent resistance of automobile body panels is an important property for automobile design and manufacture, but the study on this aspect is not still profound. This study is to summarize the testing methods and physical significations of static and dynamic dent resistance of automobile body panels combined with the author’s study, and to analyze the dent behaviors in the round. Several influence factors on dent resistance are expatiated including the mechanical properties of materials, stress states after forming, bake hardening ability, modulus, methods of testing, and structure of specimens and so on. The automotive lightweight and application of high strength steel sheets and aluminum alloys sheets are analyzed, and the significance of testing of dent resistance, especially for dynamic dent resistance of auto-panels, and the finite element simulation analysis are emphasized. To explain the physical phenomenon of dent behaviors, the latest and concerned study results are also discussed. According to this study, a dent resistance test and evaluation standard of Society of Automotive Engineers of China for automotive body panel is presented and is being carried out, and an industry conference is hold to discuss the working-out of the standard, a primary schedule of this standard is confirmed now. The study can guide the further testing and study of dent resistant of auto-panels.

Structurally strengthened aluminum alloys

Comparative analysis of the properties of semiproducts from aluminum alloys with recrystallized and nonrecrystallized structures is performed. New data showing the importance of preservation of nonrecrystallized structure (the main feature of structural strengthening) for elevation of the characteristics of strength and static and cyclic crack resistance of aluminum alloys are presented. Special features of structural strengthening of aluminum-lithium alloys are considered.

Plastic joining of dissimilar material of high tensile strength steel and aluminium alloy sheets

Plastic joining of dissimilar material of high tensile strength steel and aluminium alloy sheets

Evolution of Relevant Parameters on Fretting Fatigue Tests

The degradation process in fretting fatigue is due to mechanical and chemical attack between two contacting surfaces, being directly related to wear, corrosion and fatigue. There are many parameters that influence the fretting fatigue phenomenon out of which relative displacement, δ , normal load, n F , and tangential load t F , are the most important and consequently the most studied ones. This paper describes the fretting fatigue phenomenon occurring on a high strength aluminium alloy, Al7175. The aim of this study is to achieve a better understanding of the fretting fatigue behaviour by observing the evolution of the fatigue life of the specimen with the normal load, the tangential load and the relative displacement amplitude.

断熱鋳型半連続鋳造と機械撹拌の組合せによる高強度および難加工性アルミニウム合金半凝固ビレットの開発

断熱鋳型半連続鋳造と機械撹拌の組合せによる高強度および難加工性アルミニウム合金半凝固ビレットの開発

Experimental Study on Specimen and Grain Size Effects in Uniaxial Tension Test of Aluminum Foil

With the rapidly growing demand for the micro-thin-wall parts, the development of high accurate forming processes for very thin sheet or foil becomes more and more important. The aim of this study is to explore the effects of specimen width and grain size on tensile strength of aluminum alloy 3003 foil in uniaxial tension test. The problem was approached in two ways: firstly, by reduction of the specimen width, and secondly, by changing the grain size through annealing crystallization. The uniaxial tension tests were performed on an electronic universal material testing machine, in which a linear CCD based visual extensometer was used to measure deformation. The results show that the tensile strength decreases with decreasing specimen width or increasing surface-to-volume ratio. The tensile strength decreases with decreasing grain size for grain sizes larger than the specimen thickness.

Modification of A3003 Alloy for Development of High Toughness Al Alloy Tube

The strength of aluminum alloys was improved by a severe deformation process while the decrease of elongation leads to the defect. Modification of A3003 alloy was attempted in order to develop a high strength and high formability Al alloy tube for the application of air-conditioning systems in transportation, such as passenger planes and automobiles. An A3003 alloy was modified by Ti addition, grain refiner. As a result of modification, the modified A3003 alloy was able to suitably satisfy the mechanical strength requirements, including elongation. Grain size and secondary dendrite arm spacing of A3003 alloy decreased by as much as 50 % by Ti addition. The finer grains were uniformly distributed in the modified A3003 alloy billet. The yield strength of the modified A3003 alloy was improved by 30 % without decreasing elongation.

Study on the Erbium Strengthened Aluminum Alloy

We have systemically studied the effect of the erbium on the microstructure and the mechanical properties in the 5xxx series aluminum alloys by using optical microscope, transmission electron microscope (TEM) and by tensile testing. The results demonstrate that the tensile strength increased quickly at the beginning of small contents of 0.1%Er both in the hot and cold rolled states, then slowly increased with increasing the contents of Er until 0.4%, at which the best balance of the strength and ductility (438MPa and 9.6%) were obtained. Microstructure observation in the hot rolled state was indicated that the grain structure in the Er free Al-5Mg alloy revealed fully recrystallized grain structure, while in the Al-5Mg containing Er was demonstrated deformation structure, indicating the Er addition delayed the recrystallization behavior by the formation of the precipitation of the Al3Er, which confirmed by means of the X-ray diffraction analysis. Furthermore in the TEM microstructure observation the precipitation of Al3Er was distributed both in the grain interior and subgrain or grain boundaries, which could be pinning the subgrain or grain boundary migration and dislocation movement as well. Consequently the beginning of the recrystallization temperature in the Al-5Mg containing Er was elevated about 50°C than in Al-5Mg without Er. This could be explained that the strength increased without the deterioration of the ductility was attributed to the microstructure refinement by the Er addition.

Effect of initial temper on mechanical properties of friction stir welded Al-2024 alloy

The microstructural evolution and resultant mechanical properties during the friction stir welding (FSW) of precipitation strengthened aluminium alloys depend on initial temper as well as FSW process parameters. Al-2024 alloy under two different initial tempers, T3 and T8, was used in the present study. FSW bead-on-plate runs were performed at different values of process parameters (tool rotation rate and tool traverse speed). Microstructure and mechanical properties of the nugget region and heat affected zone (HAZ) were evaluated. Differential scanning calorimetry (DSC) revealed that in the nugget region, presence of Guinier–Preston–Bagaryatskii (GPB) zone results from the partial dissolution of Al2CuMg phase. The microstructure and tensile properties were found to be independent of the initial temper of the material in the nugget region. In the HAZ region, tensile properties increased at higher heat index values for T3 condition, and decreased monotonically for T8 condition.

Selection of Welding Process Parameters for the Optimum Butt-Joint Strength of an Aluminum Alloy

In this paper, the selection of welding process parameters for obtaining the optimum weld butt-joint ultimate tensile strength (UTS) of aluminum alloy (6061-T6) is presented. Considering weld-joint UTS as the quality characteristic in the selection of process parameters, the Taguchi method is used to analyze the effect of each individual process parameter and of their interaction and then to determine process parameters for the optimum weld-joint UTS. Analysis of variance (ANOVA) technique is applied to investigate which welding process parameter has significant effect on the weld-joint UTS. Experimental results are provided to illustrate the proposed approach.