Materials Science Forum Vol. 877

Abstract: In order to obtain the high performance materials with high thermal conductivity, high electrical conductivity, low thermal expansion, good mechanical properties and low density, TiB₂ particle dispersed aluminum (Al) composites was developed by spark plasma sintering. As these properties are affected by the dispersibility of the particles, the relationship among the dispersibility of dispersant and the thermal conductivity and mechanical properties was investigated, 20 vol. % TiB₂ dispersed Al composites with different dispersibility were fabricated by spark plasma sintering (SPS). The dispersibility was estimated quantitatively by using the definition method of local number of particles (LN2DR method), and two composites having 6.884 and 4.839 for number of LN2DR was obtained. Thermal conductivity of the composites with homogeneous distribution of TiB₂ particles was lower than that with heterogeneous distribution and clustering. On the other hand, the tensile strength of the composites improved as increasing temperature compared with Al block. Furthermore, strength of the composites with homogeneous distribution of TiB₂ particles at 200°C and more was higher than that of the composites with heterogeneous distribution and clustering.

Abstract: The microstructure solution treated by various temperatures of 2h in as-extruded Al-9.3Zn-2.0Mg-1.8Cu alloy was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The mechanical properties treated at 465^oC for various times were tested by room temperature tensile mechanical properties test. The results indicated that second phase of the as-extruded alloy mainly consists of Mg (Zn,Cu,Al)₂ and Fe-rich phases. Mg (Zn,Cu,Al)₂ phase completely dissolved into the matrix solution treated at 465^oC or higher for 2h while residual phase was mainly Fe-rich phase. The mechanical properties treated at 465^oC for various time were tested and optimized solution treatment parameter was chosen as 465°C/1.5h.

Abstract: An investigation has been performed into the compatibility of aluminum alloys used in the aerospace industry with Wire-Arc Additive Manufacturing. Modelling and preliminary experimental trials have been performed to show that it is viable to use Al-Cu-Mg alloys, like 2024, without solidification cracking. A relatively fine and texture free grain structure was obtained in the as-deposited WAAM material and the addition of inter-pass deformation, by rolling each added layer, led to further grain size refinement. With adequate control of porosity and subsequent heat treatment, the WAAM material was found to have tensile properties comparable to that of standard wrought products.

Abstract: Considering the poor plastic forming capacity of Al alloys at room temperature, this study proposed a stamping technique assisted by arc welding for partial material modification. The plastic forming capacity of the sheet pretreated by arc welding was confirmed with the V-shaped bending test. The microstructures and mechanical properties of the sheets were tested, and the cause of the increase in sheet deformability was analyzed. The Al alloy sheet pretreated by arc welding showed good plastic capacity at room temperature and under large deformations. The main advantage of arc welding is high speed, by which plastic working efficiency can be increased under certain conditions. In this technology, the difficult forming areas of structural parts are first located. Before plastic forming, sheets are pretreated by arc welding to convert the rolled grains in the softened heat-affected zones (HAZs) of the sheets into equiaxed grains and thereby regain grain deformability. Arc welding pretreatment is only used to soften difficult forming areas. Moreover, the local plasticity of sheets significantly increases in comparison with that of base metals, and the hardness of HAZs after plastic forming is improved.

Abstract: The present paper describes an innovative methodology that has been developed for optimization of product properties, production costs, and environmental impact in fabrication of aluminium alloys. The main idea is to represent each operation along the process chain by predictive models, which include material, mechanical, cost, and sustainability models. A multi-objective optimization platform is used to combine the models into a common software environment, which allows fully automatic simulations. The optimization tool runs the models in iterations until user-defined acceptance levels on properties, costs, and sustainability indices are obtained. In this paper, the methodology has been applied for fabrication of 6xxx-series aluminium extrusions. As a demonstration of practical relevance, the software tool was used to optimize mechanical properties and electrical conductivity by manipulation of alloy chemistry, processing parameters, and microstructure characteristics like grain structure, precipitates, dispersoids, and solid solution concentrations. At the same time material and production costs, as well as CO₂ emissions along the value chain were attempted to be kept at minimum levels.

Abstract: The influences of Fe content, Mn-Fe ratio and cooling rate on the β-Fe phase distribution of Al-Si-Cu casting alloy were studied. The results showed that the β-Fe phase was reduced when the cooling rate was raised. Mn can effectively refine the morphology of Fe phase. When Fe content is 0.4% and Mn-Fe ratio comes to 0.8, the needle-like β-Fe phase is transformed into fine particles or bone-shaped in different positions of the cylinder head, it can manage to the best matching of quality and cost.

Abstract: The manufacturing of AA6xxx car body panels typically consists of rolling, ageing and forming processes. Thus, multiple simulation tools can be coupled to set up a through-process modelling (TPM) framework for predicting the evolution of microstructure and the final mechanical properties of these products. In order to realize such a TPM concept, various industrial processing phenomena were studied and modelled in the open innovation research cluster “Advanced Metals and Processes” (AMAP^♯). This work focuses on the age hardening behavior which takes place during the industrial paint bake process. To reflect the microstructure evolution of this processing step, a multi-component precipitation model is developed. So far, the influences of thermomechanical processes, i.e. annealing temperature on the kinetics of Mg_xSi_y precipitates during artificial aging were implemented. The precipitation model was linked to a yield strength model in order to simulate the evolution of mechanical properties within the TPM framework. For validation, the evolution of microstructure and mechanical properties of an AA6016 alloy during artificial ageing was investigated via transmission electron microscopy (TEM) and tensile testing. The simulation results are in agreement with experimental observations.

Abstract: The quenching process can produce great residual stresses in 7055 aluminum alloy plates. The main factor that affects the quenching residual stresses is the heat transfer coefficient in the quenching process. In this paper, the heat transfer coefficients of spray quenching under different spray water flows were measured by using the inverse method, and the heat transfer coefficients of immersion quenching under different water temperatures were measured by the iterative method. The heat transfer coefficient increases as the spray water flow increases while decreases as the water temperature increases. The basic differences of water temperatures/spray water flows/quenching methods are the different heat transfer coefficients. According to the heat transfer coefficients results of immersion and spray quenching, an orthogonal test was carried out to study the effects of heat transfer coefficients in different temperature regions on the quenching residual stresses. The heat transfer coefficients in the range of 100oC ~200oC have a great influence on the quenching residual stresses, especially for the heat transfer coefficient near 150oC.

Abstract: Magnetic pulse welding (MPW) which is one of the impact welding methods is suitable for a wide variety of combinations of similar and dissimilar metals. The flyer plate is accelerated by electromagnetic force and collided to the parent plate. A characteristic wavy interface is formed. The impact velocity and impact angle of the flyer plate during impact are important parameters which affect the interface morphology. In the case of dissimilar metals (e.g. Al/Cu, Al/Fe), the intermediate layer (such as intermetallic compound (IMC)) is formed by wavy interface formation and local temperature increase. The intermediate layer often decreases the bonding strength. Wavy interface formation mechanism and temperature increase at the joint interface should be investigated in order to obtain the dissimilar metal joint with high bonding strength. In this study, the impact velocity and impact angle of the flyer plate were obtained by using ANSYS Emag-Mechanical. Based on the obtained impact velocity and impact angle of the flyer plate in the MPW, the wavy interface formation and temperature change were reproduced by using ANSYS Autodyn for solving non-liner dynamics problems. Al sheets and Cu sheets were joined by the MPW. The joint interface was observed by OM and SEM and compared to the simulation result.

Abstract: In the current work, the recently proposed homogeneous anisotropic hardening (HAH) model, featuring a distorted yield surface, is applied to commercially pure aluminium. A dislocation-based hardening rule is incorporated into the HAH model to describe the transient stagnation of the hardening rate during strain reversal. A cast and homogenized material with random texture previously investigated by Mánik et al. [1] is selected. The material is prestrained either by compression or rolling, and then tested in uniaxial tension to acquire either reverse softening or orthogonal hardening. The Bauschinger effect, the permanent softening during reverse loading and the hardening in the course of orthogonal loading are captured by the model. However, the permanent softening during orthogonal loading cannot be predicted, and the transient variations of the R-value predicted by the HAH model are neither in qualitative nor quantitative agreement with the experimental data.