Various challenges such as new technologies, growing complexity and competitive environment, require the main contractor to assign some of the project’s tasks to other parties, the so-called subcontractors. Although subcontract­ing is a usual phenomenon in the construction industry, insufficient attention to the subcontractor selection strategy may pose some major threats to a project. Having in mind the significance of such risks, the optimization of subcontractor selection is essential for the success of the project. The importance of risk management in selecting subcontractors and the direct relation between risks and returns in most projects are two main motives for using the concept of portfolio in this paper. The main objective of this paper is to propose a model to allocate the best portion of project’s task to some subcontractors in order to reach the optimized portfolio of subcontractors and main contractor. This is a new approach in the subcontractor management; therefore, after presenting the model, an illustrative example will be presented for better understanding.

This work gives an insight into the transient softening at the fusion boundary of resistance spot welds on hot stamped steel. Metallographic investigations and hardness mapping were combined with finite phase–field modeling of phase evolution at the fusion boundary. Saturation of weld nugget growth in the welding process was observed. For industrially relevant, long welding times, the fusion boundary of a spot weld is therefore isothermally soaked between the peritectic and solidus temperatures. This leads to a carbon segregation to the liquid phase due to higher carbon solubility and possibly to δ-Fe formation at the fusion boundary. Both results in a local carbon depletion at the fusion boundary. This finding is in good agreement with carbon content measurements at the fusion boundary and the results of hardness measurements.

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The aim of the present study is to identify the ternary eutectic Mo-Si-B composition to produce directionally solidified materials, which are expected to have excellent high-temperature properties due to the well-defined microstructure. Different alloy compositions in the respective primary solidification areas of the phases were chosen to investigate the microstructural evolution. The results were compared to thermodynamic calculations of the liquidus projection and isopleth phase diagrams using the software FactSageTM. By carrying out these experiments the eutectic point was found to have a nominal composition of Mo-17.5Si-8B (at.%). In the next step, the eutectic alloy was directionally solidified by a zone melting (ZM) process. The evolution of a typical eutectic microstructure due to the growth of lamella-like structures is shown by microstructural investigations. Furthermore, we present a eutectic phase field model for the eutectic Mo-Si-B alloy. The equilibrium interface geometries and interface mobility were calculated using an isotropic model. The results are shown to be in an adequate conformity with the experimental observations.