Field’s metal, a low-melting-point eutectic alloy composed of 51% In, 32.5 Bi% and 16.5% Sn by weight and with a melting temperature of 333 K, is widely used as liquid metal coolant in advanced nuclear reactors and in electro–magneto–hydrodynamic two-phase flow loops. However, its rheological and wetting properties in liquid state make this metal suitable for the formation of droplets and other structures for application in microfabrication. As with other low-melting-point metal alloys, in the presence of air, Field’s metal has an oxide film on its surface, which provides a degree of malleability and stability. In this paper, the viscoelastic properties of Field’s metal oxide skin were studied in a parallel-plate rheometer, while surface tension and solidification and contact angles were determined using drop shape analysis techniques.

The rear wall of the header box serves as a tubesheet in heat exchangers of double plate header box. Tube-to-tubesheet welding must be performed using orbital Gas Tungsten Arc Welding (GTAW) with a head extension, which is passed through the corresponding hole in the front wall (plugsheet) of the header box, where the welding machine is supported. In this project, the effect of parallelism deviations between the plugsheet and the tubesheet of carbon steel header box is analyzed to evaluate its influence on the quality of the tube-to-tubesheet welding. Welded tube (SA-210 Gr. A1) to tubesheet (SA-516 Gr. 70) coupons are manufactured simulating the parallelism deviations previously analyzed in two double plate header boxes of air-cooled heat exchangers using two different preheating temperatures. Macrographic analysis is performed in order to evaluate the weld penetration (minimum leak path) and length of the weld leg in tube-to-tubesheet joints. The results obtained show important variations in those parameters when the parallelism deviations are equal to or greater than −1 mm over the theoretical distance as well as when the distance approaches +1 mm or more. Finally, the incorporation of dimensional controls prior to the welding process is discussed and the implementation of improvements in orbital GTAW equipment is recommended as an optimal solution for this kind of heat exchangers.

The development of a facility for the generation and deposition of molten metal droplets of small size (on the order of 1 mm) is described. The facility will allow accurately synchronize the instants at which the micro droplets are generated and fall in the vertical deposition direction (Z axis) with the movement (X and Y axes) of the substrate located below the micro-droplet generator. A great challenge of this type of processes is to find optimal operating conditions that allow us to manufacture with sufficient accuracy tridimensional metallic micro structures, more or less complex, which can be of interest in the electronic or additive manufacturing industry. These optimal conditions are affected by many factors including the oxidation phenomena that usually occur in many liquid metals. These oxidation phenomena tend to form an oxide layer on the molten metal surface exposed to the ambient air, which may greatly modify the viscosity, wetting capability or surface tension of the liquid droplet. A detailed analysis of the effect of the oxygen content in the atmosphere where the experiments are made on the outcome of the droplet impact on a solid surface is carried out in this work. The results of this analysis show a strong influence of the surface oxidation on the droplet dynamics before and after the impact