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The evolution of heat transfer coefficient (HTC) in the sand casting of A357 aluminium alloy against aluminium chills is evaluated with different metal heads to study the effect of pressure on the HTC. Inverse modelling techniques based on Beck's analysis were used to determine the experimental evolution of HTC as a function of time, casting temperature and chill temperature. The experiments were reconstructed by means of numerical analyses to determine the best way to fit the experimental data. Two approaches were considered: in the first, a simple thermal analysis of the solidification was carried out with the HTC depending on both the interface casting temperature and the effective metal head as determined from the experiments; in the second, a coupled thermal stress analysis was performed with the HTC dependent on the interface pressure. [ABSTRACT FROM AUTHOR]

Abstract: An extensive investigation of the correlation between die design and the extrusion process of AA6082 aluminum alloy is presented. A profile with a central seam weld line suitable for mechanical testing is extruded under different processing conditions, by varying the dimensions of the die feeder, the length of the welding chamber, the billet preheating temperature and the process speed. For each condition the workability area was defined by detecting tearing defects in the production stage. Tension tests were then carried out on the extruded profiles, to evaluate the effect of the geometrical features of the die, so that an interpretation could be made of the influence of each parameter in a wide spectrum of operating conditions. In particular, tensile strength and equivalent fracture strain were evaluated on the final product to assess the effectiveness of welding. [Copyright &y& Elsevier]

Abstract: An extensive experimental investigation on the heat transfer coefficient (HTC) during sand casting of aluminum alloy is presented here; the variation in time of the HTC in the whole cooling process was reconstructed with many kinds of chills, different in size and material. Cast iron, aluminum and copper were used as chill materials, the HTC between aluminum and sand also being considered. In particular, typical foundry practice regarding melt treatment, sand preparation and chill manufacturing and assembly within the mold is considered throughout the analysis, in order to obtain the most reliable HTC values. The evaluated HTC are then put in relation with cast and chill temperature, in order to allow the easiest transportability to simulation codes for foundry. Relevant points of HTC curves and physical behaviors of the interfaces are also discussed. [Copyright &y& Elsevier]

The first review and comparison of methods for evaluating the quality of seam welds in aluminum extruded profiles is here presented. In fact, although the solid state welding of the seams in the extrusion of aluminum hollow profiles affects the process productivity, the profile resistance and the aspect of the surface, a general methodology for weld quality prediction has, so far, not been presented. This work reconstructs the experiences of other researchers on a AA 6082 aluminum alloy by means of thermo-mechanical FEM analyses, with the aim to evaluate the fields of pressure, flow stress and velocity on the welding surface. On this basis, different welding criteria were applied in order to evaluate their ability to describe the observed phenomena. Some criteria showed a good relation between simulations and tests, thus evidencing good predicting capabilities. [Copyright &y& Elsevier]