PULVIMETALURGY

Author: MONTEALEGRE AGUADO M. ANGELES.
Year: 2004.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS QUÍMICAS.
Place of preparation: CENTRO NACIONAL DE INVESTIGACIÓN METALÚRGICAS.

Summary: The gradual increase in life expectancy of the population motivates the development of new biomaterials, or improving existing ones through superficial modifications, capable of extending the service life of the materials in uso.En this work has been characterized alloys FEA1CR, that could be coated with alumina by thermal oxidation, which have been developed as potential biomateriales.Durante oxidation alloy develops a layer of alumina alpha type, but very thin adherida.La generation of this layer is accompanied by very high tensions compression to improve the resistance to fatiga.Dichas tensions allow deformations in the material without cracking up 1,2-1,4% of the layer. Moreover, we have developed new alloys intermetálicas not ferromagnéticas whose preparation on an industrial scale is carried out later by pulvimetalurgia.La memory incorporates studies of oxidation and mechanical behavior of these alloys, and its interpretation in terms of the microstructural .El tamaño de grano de estas aleaciones se mantiene en el orden de 1-2 micras gracias a la presencia de una pequeña fracción de itria, que además contribuye a los elevados valores de dureza (=400Hz).Un aspecto a destacar de estas aleaciones that is, despite it intermetallic compounds (known for their low ductility), has been found in one of the alloys values ductility of 5%, with a yield strength of about 1000MPa.Estas alloys are able to generate a layer only alumina treatments through oxidation térmica.La kinetics and morphology of the same depends on the temperature oxidation; to 900c prevails phase metaestable 0 and 11000c the alfa-AL2O3. Studies oxidation in two stages by oxygen isotopes show that the diffusion layer grows anion.

Author: ANTOLIN GANUZA RAQUEL.
Year: 2004.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE CIENCIA Y TECNOLOGIA.
Place of preparation: FACULTAD DE CIENCIA Y TECNOLOGIA.

Summary: As part of the optimization methods and analytical processes aimed at the attainment of ISO17025 in the Analytical Laboratory of the company Bostlan SA, have addressed the following tasks. First, it has been optimized and validated the method of analysis of particle size by difractómetro laser for metal powders and fluxes used in Bostlan. Within this work, the conditions are optimized instrumental measurement, and have equated the action to those obtained through sieves tower, which is the technical reference. It has also prepared an internal reference material for statistical process control measure. The second task is related to the optimization and validation of methods used in the elemental analysis of raw materials. Within this task, have addressed the following aspects: the selection of wavelengths for the measure by atomic emission (PKI), the digestion of the samples using microwave targeted; optimization system hydride generation / ICP for determining Se and As, Hg, Sn ... the preparation of a reference material for internal control statistic is in the determination of manganese; validation system espectofotometria spark with the PKI, and the intercomparison of the results obtained by the laboratories of customers. The third task is an example of a practical application that integrates all aspects discussed above in order to improve the product manufactured in Bostlan.

Author: ISTURIZ MOTA ALVARO ORLANDO.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: Salon de actos CTM-EUPM.
Place of preparation: ETSEIB, PAVELLÓ E Campus SUD.

Summary: This research project is part of a line of research that considers long-range study of the whole process pulvimetalúrgico manufacturing industrial components and their effect on the mechanical properties of the resulting product. The stages of the process pulvimetalúrgico are: filling of the mold, transfer, scavenging dust, mold removal and sintering. This study focuses on the two initial stages of the process of compaction pieces pulvimetalúrgicas, which highlights among the least researched stages of the process. The intermediate stage of compacting and has been the subject of numerous studies, while the final phase, or stage of expulsion, begins to be currently under investigation. To do so, within the context of this project is built Experimental setup laboratory that reproduces both processes, the filling of the mold and transfer. So, it has an experimental system that can reproduce both processes in a controlled manner and with which it is possible to study the behavior of a large number of granular materials. The tests conducted in this study have allowed distinguish different flow regimes during filling both arenas as metal powders, understand the influence of the shape and dimensions of the mold, as well as the morphology and particle size, density apparent. Thus, there are three regimes filling different as a function of speed filling and particle size of the material. A regime of continuous filling at high speeds and a system of filling discreet at low speeds. Lastly, there is an intermediate regime between the two, or intermittent flow regime, which coexist properties of continuous regime and the regime discreet. In addition to the tests that have allowed filling distinguish three types of flow regimes have been conducted tests to measure the mass flow in each one of these regimes. These tests have enabled a better characterization of these regimes are as showing variations in the flow in each case. Moreover, there have been various mechanisms friccionales associated with the transfer process. Stand out in this way two complementary mechanisms to coexist during the transfer process, those being: transfer mechanism and shear mechanism or no-transferencia. The factor that determines which is the dominant mechanism is the width of the spike, found that wide media punch two mechanisms coexist in favor of a partial transfer. For hallmarks thin is a mechanism for shear, or no-transferencia, while for wide punches dominated the transfer mechanism, favors an efficient transfer. On the other hand considers the presence of shear bands in the interior of the material in areas close to both shear forced by the transfer process. The width of these bands is related to the particle size of the material as much as the width of the spike employee. The results obtained by studying both processes have been employed in the development and validation of a numerical model proposed by a group of friends of the UPC (CIMNE, International Center for Numerical Methods in Engineering). Here is a high degree of correspondence between the experimental results and simulations in the case of continuous filling regime during the filling and in the whole of the transfer stage.

Author: Gonzàlez Gasch Alex.
Year: 2005.
University: GIRONA [www.udg.es].
Place of defense: Escola Politecnica Superior, Universitat de Girona.
Place of preparation: Escola Politècnica Superior - Univeristat de Ciències.

Summary: The alloy solidification and mechanical quick two techniques are conducive to the formation of alloys metaestables nanocristalinas. In this paper we have produced alloys by both techniques, with a membership of Fe- (Ni, Co) -MB where (M = Nb, Zr). It has studied the temporal evolution of the production of alloys, as well as the final result. The evolution of the milling process has been a refinement of the grain boundaries until manometric (10 nm). It has analyzed the structure and morphology of the phases present in the aleacions. To that end, studies were conducted differential scanning calorimetry (DSC), termogravimetria (TG), termogravimetria magnetic (TGM), X-ray Diffraction (XRD), spectroscopy Mà ¶ ssbauer transmission (TMS), and scanning electron Microscopy transmission (SEM, TEM). It has been found that the result of the production process is a solid solution nanocristal lina structure of the body centered cubic (BCC) based iron. We have seen the influence of various elements in the evolution of the grinding process and the end result, for example, the inclusion of nickel favors the formation of an amorphous phase minority. It has studied the thermal stability of the alloys by heat treatment at various temperatures. It has been found that the resulting alloys are stable over a wide temperature range. For temperatures above 900 ° C is the emergence of a new phase fcc-Fe-Ni It has been shown through thermodynamic modeling that the results obtained by mechanically alloyed are different from the results close to balance. The phases obtained through both tracks are different. The Milling tape obtained by rapid solidification, has been demonstrated as an alternative route alloys obtained by mechanical alloying, although it decreases the thermal stability of the alloys.