https://hdl.handle.net/10259/8139 Mon, 20 Apr 2026 19:36:36 GMT 2026-04-20T19:36:36Z https://hdl.handle.net/10259/8183 Influence of Porosity in the Fatigue Behavior of the High-Pressure Die-Casting AZ91 Magnesium Alloys Preciado Calzada, Mónica; Bravo Díez, Pedro Miguel; Cárdenas Gonzalo, David The fatigue properties of high-pressure die-casting (HPDC) magnesium (Mg) alloys AZ91 exhibit a high variability, due primarily to the porosity that is inherent in the injection process. In the 94% of the studied samples, the porosity in which crack nucleation originates is at the surface or adjacent to the surface. The threshold stress intensity factor amplitude and the limit of fatigue have been calculated following the classical models of parameterization of defects. A new set of samples were prepared by machining the surface slightly, in order to conserve the microstructure, and the fatigue behavior at low level of stress was improved. All the samples were produced in molds with the final shape by HPDC process, which allowed a realistic study of the surface effect and the influence of grain size variation from the edge to the center of the samples. Sat, 01 Oct 2016 00:00:00 GMT https://hdl.handle.net/10259/8183 2016-10-01T00:00:00Z https://hdl.handle.net/10259/8175 Change of mechanical properties of AM60B alloy with heat treatments and its correlation with small punch tests Bravo Díez, Pedro Miguel; Preciado Calzada, Mónica; Cárdenas Gonzalo, David; Calaf Chica, José AM60B alloy, injected by high pressure die casting process (HPDC), is one of the most widely used alloys for its ease of processing and low price. There is an industrial interest in the use of heat treatments in order to increase the elongation before failure of the alloy. This paper aims to correlate the results of tensile test of heat treated specimens with small punch tests (SPT’s). It is also intended to find out if the different characteristic values of such tests for different mechanical properties are sensitive enough to detect changes produced by heat treatments or injection process parameters and if the correlation factors are sufficiently stable. In addition, this study is also focused on the validation of the applicability of such miniature tests for high pressure die casting magnesium alloys, since this process introduces a significant number of defects and thus a variability of the mechanical properties is expected. Thu, 01 Dec 2016 00:00:00 GMT https://hdl.handle.net/10259/8175 2016-12-01T00:00:00Z https://hdl.handle.net/10259/8174 Deep cryogenic treatment of HPDC AZ91 magnesium alloys prior to aging and its influence on alloy microstructure and mechanical properties Preciado Calzada, Mónica; Bravo Díez, Pedro Miguel; Cárdenas Gonzalo, David Studies of deep cryogenic treatment have mainly focused on ferrous alloys, despite the advantages of this form of treatment when applied to other non-ferrous alloys. This study examines the microstructural behavior of a high pressure die-casting (HPDC) AZ91 magnesium alloy, submitted to T6 and T6 with deep cryogenic treatment (DCT) prior to aging. Differences between continuous and discontinuous β-Mg17Al12 phase precipitation are analyzed by means of TEM, SEM and optical microscopy to explain the mechanical behavior following each type of heat treatment. The mechanical properties were improved by both treatments though yield strength was higher following T6 treatment and elongation was greater following T6 with deep cryogenic treatment. The conclusion is that continuous precipitation is promoted by cryogenic treatment, resulting in an improvement of elongation by 20%. This factor is important in view of the limitations of poor plasticity and its consequences for HPDC magnesium alloy applications. Sun, 01 Jan 2017 00:00:00 GMT https://hdl.handle.net/10259/8174 2017-01-01T00:00:00Z https://hdl.handle.net/10259/8163 Las cargas familiares y el estrés laboral Cárdenas Gonzalo, David; García Herrero, Susana; Mariscal Saldaña, Miguel Ángel; Gutiérrez Llorente, José Manuel Uno de los aspectos que ha condicionado la realización de este artículo, ha sido la influencia sobre el estrés en la combinación de las cargas familiares y laborales y de sus consecuencias directas en el mundo laboral y familiar. En este estudio, se han expuesto variables importantes que afectan al estrés dentro de la familia como el cuidado de niños, el cuidado de personas mayores y la realización de tareas domésticas del hogar. Por otro lado, y de manera directa con el mundo laboral, se ha podido comprobar que el ritmo de trabajo por si solo, afecta sobre el estrés y mucho más aún en combinación con las cargas familiares como el cuidado de niños, el cuidado de mayores y la realización de las tareas domésticas del hogar. Con respecto a las cargas laborales, el estudio realizado asegura que la variable ritmo de trabajo es la más influyente sobre la probabilidad de sufrir altos niveles de estrés tanto por si sola como en combinación con las cargas familiares. Los resultados obtenidos demuestran que la combinación de todas estas variables pueden generar altos niveles de estrés que repercutirán tanto en el mundo laboral como el familiar. Realizar estudios de sensibilidad de las combinaciones entre las variables más desfavorables, en este sentido, va a permitir controlar directamente los niveles de estrés sufridos por las personas tanto en la familia como en el trabajo. De esta manera, se podrá actuar sobre esas variables, tanto familiares (cuidado de personas mayores, cuidado de niños y realización de tareas del hogar) como laborales (ritmo de trabajo) para conseguir reducir en lo posible la probabilidad de sufrir altos niveles de estrés. Sun, 01 Mar 2015 00:00:00 GMT https://hdl.handle.net/10259/8163 2015-03-01T00:00:00Z