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In this paper, the process known as Electrical Resistance Sintering under Pressure is modelled, simulated and validated. This consolidation technique consists of applying a highintensity electrical current to a metallic powder mass under compression. The Joule effect acts heating and softening the powders at the time that pressure deforms and makes the powder mass to densify. The proposed model is numerically solved by the finite elements method, taking into account the electrical-thermal-mechanical coupling present in the process. The theoretical predictions are validated with data recorded by sensors installed in the electrical resistance sintering equipment during experiments with iron powders. The reasonable agreement between the theoretical and experimental curves regarding the overall porosity and electrical resistance suggests that the model reproduces the main characteristics of the process. Also, metallographic studies on porosity distribution confirm the model theoretical predictions. Once confirmed the model and simulator efficiency, the evolution of the temperature and the porosity fields in the powder mass and in the rest of elements of the system can be predicted. The influences of the processing parameters (intensity, time and pressure) as well as the die material are also analyzed and discussed.

This paper focuses on the microstructural characterization of Al25Ti75, Al37Ti63, Al50Ti50, Al63Ti37and Al75Ti25powders mixtures prepared by mechanical alloying (MA). The high-energy ball-milling, up to 75 h, of aluminium and titanium powders leads to a nanocrystalline or an amorphous structure. It is showed that a stable amorphous Al–Ti phase with uniform elemental distribution forms after 50 h of milling in Al50Ti50alloy. Heat treatment of the different alloys leads to the crystallization of AlTi3, AlTi, Al2Ti and Al3Ti intermetallic compounds. A comprehensive study by laser granulometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) was carried out on the structure, surface morphology and thermal behaviour of the MA Al-Ti mixtures, both of milled and heat treated powders.

In order to produce metal matrix composites (MMCs), aluminium powder was milled for a total time of 5 hours. Aluminium nitride was the ceramic reinforcement chosen to improve the mechanical behaviour of the aluminium matrix. In order to form it in situ, an ammonia gas flow was incorporated during a certain period of the milling process. Two different conditions of NH3 flow during milling were studied: short time (5 min) and long time (3 h). In both cases, milling started with a 2 h period of mechanical alloy in vacuum (5 Pa). Then, NH3 was incorporated during the stipulated time (5 min or 3 h), after which the milling process continued under vacuum to complete 5 hours. The powders were cold pressed and vacuum sintered to produce compacts. The results showed that compacts with better mechanical properties are obtained when short duration ammonia gas flow is used. The use of short flows provides good control of the amount of ceramic second phases formed. This allows the produced compacts to reach ultimate tensile strength higher than 400 MPa.