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Estación Coahuila, Mexico

Hung N.P.,Texas A&M University | Velamati M.,Texas A&M University | Aguilar E.,COMIMSA | Garza-Castanon M.A.,COMIMSA | Powers M.,Agilent Technologies
TMS Annual Meeting | Year: 2011

Advanced aluminum graphite composites have unique thermal properties due to opposite coefficients of thermal expansion of aluminum and graphite. The thermal and mechanical properties of such composites are anisotropic due to directional properties of graphite fibers and their designed orientation. A joint of components with different fiber orientations would theoretically produce an isotropic material for thermal management purpose. This paper presents research results for welding and brazing of the composite using different joining techniques. A laser beam melts the matrix and delaminates graphite fibers. The molten aluminum reacts with graphite to form aluminum carbide Al4C3. The joint strength is compromised when laser welding at optimal conditions to minimize the carbide formation. Brazing is preferred since the low melting temperature of a filler material suppresses the formation of Al4C3 while minimizing shrinkage cavities in the joint. Microstructural study and shear test confirm the success of joining this composite by laser brazing and resistance brazing with Zn-Al filler. Source

Lopez V.,COMIMSA | Reyes A.,COMIMSA | Zambrano P.,Autonomous University of Nuevo Leon
Applied Mechanics and Materials | Year: 2013

The effect of heat input on the transformation of retained austenite steels transformation induced plasticity (TRIP) was investigated in the heat affected zone (HAZ) of the Gas Metal Arc Welding GMAW process. The determination of retained austenite of the HAZ is important in optimizing the welding parameters when welding TRIP steels, because this will greatly influence the mechanical properties of the welding joint due to the transformation of residual austenite into martensite due to work hardening. Coupons were welded with high and low heat input for investigating the austenite transformation of the base metal due to heat applied by the welding process and was evaluated by optical microscopy and the method of X-Ray Diffraction (XRD). Data analyzed shows that the volume fraction of retained austenite in the HAZ increases with the heat input applied by the welding process, being greater as the heat input increase and decrease the cooling rate, this due to variation in the travel speed of the weld path. © (2013) Trans Tech Publications, Switzerland. Source

Gonzalez-Gonzalez D.S.,COMIMSA | Praga Alejo R.J.,COMIMSA | Cantu-Sifuentes M.,COMIMSA | Torres-Trevino L.M.,Autonomous University of Nuevo Leon | Mendez G.M.,COMIMSA
Applied Soft Computing Journal | Year: 2014

Since some assumptions such as the function (·) needs to be completely specified and the relationship between μ and (s) must have linear behavior in the model μ = a + b(S) used in the accelerated life testing analysis, generally do not hold; the estimation of stress level contains uncertainty. In this paper, we propose to use a non-linear fuzzy regression model for performing the extrapolation process and adapting the fuzzy probability theory to the classical reliability including uncertainty and process experience for obtaining fuzzy reliability of a component. Results show, that the proposed model has the ability to estimate reliability when the mentioned assumptions are violated and uncertainty is implicit; so that the classical models are unreliable. © 2013 Elsevier B.V. Source

Trujillo-Vazquez E.,National Polytechnic Institute of Mexico | Pech-Canul M.I.,National Polytechnic Institute of Mexico | Gonzalez L.A.,National Polytechnic Institute of Mexico | Lopez-Honorato E.,National Polytechnic Institute of Mexico | Hernandez-Garcia H.M.,COMIMSA
Materials Science Forum | Year: 2013

This paper presents results of the microstructure characterization and evaluation of physical and mechanical properties of Al/SiCp composites - intentionally containing the Al4C3 phase - prepared by pressureless infiltration, as well as results of treating the composites by the hybrid system chemical vapor deposition (HYSYCVD) route using Na2SiF6 as solid precursor. It also contains thermodynamic feasibility calculations (using the HSC 6.1™ program) of possible reactions between the SiFx(x=1-4) gas species (produced during the thermal decomposition of Na2SiF6), Al4C3 and N2 in the atmosphere. The composites were fabricated using an L4 Taguchi experimental design, infiltrating SiCp porous preforms at 1100 and 1200 °C in ultra high purity (UHP) argon and nitrogen (Ar→N2) atmosphere for 90 and 120 min, with the Al-6Si-16Mg (wt. %) alloy. The specimens were characterized by XRD, SEM and EDS. Results show that the composites exhibit a surface hardness between 63.95 and 86.5 (HR30T) and Young ́s modulus up to 118.2 GPa. Application of a post-processing stage by HYSYCVD led to the elimination of Al4C3 and the formation of a coating of stable phases on the composites' surface. The experimental results confirm the thermodynamic feasibility of the proposed chemical reactions. © (2013) Trans Tech Publications, Switzerland. Source

Verdera D.,Technology Center | Rey P.,Technology Center | Garcia F.,COMIMSA | Saldana R.,COMIMSA
TMS Annual Meeting | Year: 2015

Friction Stir Processing is a useful tool to produce composite material. By friction stirring ceramic particles into an aluminum matrix it is possible to obtain functional surfaces with an improved performance compared with monolithic alloy. In this work, nano-particles of TiC (2% in weight) were added to aluminum alloy AA7075 to produce functional surface composite material. Different processing conditions were tested (number of passes, direction of each pass, sealed or unsealed groove, etc.) in order to find out the most suitable way to uniformly disperse the particles inside the matrix. Two different kinds of samples were compared: 7075 matrix plus an addition of 7075 powder, and 7075 matrix plus an addition of 7075 powder mixed with nanoparticles of TiC. Micrographs, microhardness and wear resistant tests show the properties of the composite material made by means of friction stir processing. Source

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