Browsing by Author "Guraya, Teresa"
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Item Compound Formation and Microstructure of As-Cast High Entropy Aluminums(2018-03-09) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Koval, Natalia; Garcia, Jose; CIRMETAL; PROMETALThe aim of this work is to study the microstructure of four high entropy alloys (HEAs) produced by large scale vacuum die casting. Al40Cu15Mn5Ni5Si20Zn15, Al45Cu15Mn5Fe5Si5Ti5Zn20, Al35Cu5Fe5Mn5Si30V10Zr10, and Al50Ca5Cu5Ni10Si20Ti10 alloys formed a mixture of different structures, containing intermetallic compound (IC) and solid solution (SS) phases. The phases observed in the casting alloys were compared with the equilibrium phases predicted by Thermo-Calc. The measured densities varied from 3.33 g/cm−3 to 5.07 g/cm−3 and microhardness from 437 Hv to 887 Hv. Thus, the microhardness and estimated strength/density ratios are significantly higher than other lightweight high entropy alloys (LWHEAs).Item Design, Microstructure and Mechanical Properties of Cast Medium Entropy Aluminium Alloys(2019-12-01) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Acuña, Eva Maria; CIRMETAL; PROMETALIn this work, the design, microstructures and mechanical properties of five novel non-equiatomic lightweight medium entropy alloys were studied. The manufactured alloys were based on the Al65Cu5Mg5Si15Zn5X5 and Al70Cu5Mg5Si10Zn5X5 systems. The formation and presence of phases and microstructures were studied by introducing Fe, Ni, Cr, Mn and Zr. The feasibility of CALPHAD method for the design of new alloys was studied, demonstrating to be a good approach in the design of medium entropy alloys, due to accurate prediction of the phases, which were validated via X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. In addition, the alloys were manufactured using an industrial-scale die-casting process to make the alloys viable as engineering materials. In terms of mechanical properties, the alloys exhibited moderate plastic deformation and very high compressive strength up to 644 MPa. Finally, the reported microhardness value was in the range of 200 HV0.1 to 264 HV0.1, which was two to three times higher than those of commercial Al alloys.Item Different Phenomena Encountered during Dilatometry of Low-density Steels(2021-11-22) Jimbert, Pello; Guraya, Teresa; Kaltzakorta, Idurre; Gutiérrez, Teresa; Elvira, Roberto; Tafaghodi Khajavi, Leili; CIRMETALIn recent decades, highly alloyed low-density steels are being developed to reduce the weight of different automotive parts. Dilatometry can be a very useful experimental technique to understand phase transformations during heating or cooling of new low-density steel alloys. When performing dilatometry measurements some assumptions are made such as the homogeneity of the sample material tested during the experiment. In this study, dilatometry tests were performed for two different low-density steels, and the variations of the composition between the surface and the inner part of the sample were analyzed. The migration of manganese by diffusion from the interior of the samples and finally its evaporation on the surface under vacuum were observed. This compositional gradient generated in the samples may influence the veracity and interpretation of the results obtained in dilatometry when working with high manganese steel alloys. The detachment of surface grains created by this compositional change near the surface of the samples is also investigated.Item Evolution of Microstructure during Isothermal Treatments of a Duplex-Austenitic 0.66C11.4Mn.9.9Al Low-Density Forging Steel and Effect on the Mechanical Properties(Multidisciplinary Digital Publishing Institute (MDPI), 2021-01-26) Kaltzakorta, Idurre; Gutierrez, Teresa; Elvira, Roberto; Jimbert, Pello; Guraya, TeresaIn the last decades, low-density steels for forging have increasing interest in the automotive industry, and good mechanical properties are required for their real application. This paper describes the results obtained for a 0.66C11.4Mn9.9Al duplex austenitic low-density steel after applying a set of isothermal treatments at different combinations of time and temperature, aimed to promote kappa carbide precipitation, and improve the mechanical properties obtained with a water quenching treatment. The effects of the different isothermal treatments on the microstructure and on the mechanical properties have been analyzed and compared to those obtained from a quenching heat treatment. We found that isothermal treatments in the range temperature between 550–750 °C promoted the profuse precipitation of coarse kappa carbides at grain boundaries, which dramatically reduced the ductility of the alloy, whereas a traditional quenching treatment resulted in a better combination of ductility and mechanical strength.Item Manufacturing and forging issues encountered while upscaling 1.3C30Mn10Al-austenitic and 0.65C12Mn-duplex low-density steels(2021-07) Kaltzakorta, Idurre; Gutierrez, Teresa; Elvira, Roberto; Jimbert, Pello; Guraya, Teresa; CIRMETALDifficulties found when manufacturing and forging two low density steels in different scales are described in this work. Austenitic and duplex low-density steels have attracted a lot of interest due to their good combination of mechanical properties and density reduction. In this work, the fabrication of 1.3 C30Mn10Al austenitic low-density steel and 0.65 C12Mn10Al duplex low-density steel have been studied. The scaling up of the manufacturing process from 1 Kg to 35 Kg ingots of both materials and the subsequent hot forging of the ingots is described, showing the difficulties encountered during the production and transformation of these steels. Only the small ingots were successfully forged, but not the larger ones, showing the important differences in the forging properties depending on the geometry and dimensions of the final part to be forged, and the homogenization temperatures. The possible causes of this scale dependence are proposed from the experimental results obtained, as well as from the hot axial compression tests and the thermodynamic simulations carried out.Item Microstructure and Phase Formation of Novel Al80Mg5Sn5Zn5X5 Light-Weight Complex Concentrated Aluminum Alloys(2021-12-01) Sanchez, Jon Mikel; Pascual, Alejandro; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Galarraga, Haize; CIRMETAL; PROMETALIn this work, three novel complex concentrated aluminum alloys were developed. To investigate the unexplored region of the multicomponent phase diagrams, thermo-physical parameters and the CALPHAD method were used to understand the phase formation of the Al80Mg5Sn5Zn5Ni5 , Al80Mg5Sn5Zn5Mn5 , and Al80Mg5Sn5Zn5Ti5 alloys. The ingots of the alloys were manufactured by a gravity permanent mold casting process, avoiding the use of expensive, dangerous, or scarce alloying elements. The microstructural evolution as a function of the variable element (Ni, Mn, or Ti) was studied by means of different microstructural characterization techniques. The hardness and compressive strength of the as-cast alloys at room temperature were studied and correlated with the previously characterized microstructures. All the alloys showed multiphase microstructures with major α-Al dendritic matrix reinforced with secondary phases. In terms of mechanical properties, the developed alloys exhibited a high compression yield strength up to 420 MPa, high compression fracture strength up to 563 MPa, and elongation greater than 12%.Item Phase prediction, microstructure and high hardness of novel light-weight high entropy alloys(2019-01) Sanchez, Jon Mikel; Vicario, Iban; Albizuri, Joseba; Guraya, Teresa; Garcia, Jose Carlos; CIRMETAL; PROMETALGuided by CALPHAD modeling, low-density and multiphase three novel High Entropy Alloys (HEAs), Al40Cu15Cr15Fe15Si15, Al65Cu5Cr5Si15Mn5Ti5 and Al60Cu10Fe10Cr5Mn5Ni5Mg5 were produced by large scale vacuum die casting. A mixture of simple and complex phases was observed in the as-cast microstructures, which demonstrates good agreement with CALPHAD results. The measured densities varied from 3.7 g/cm3 to 4.6 g/cm3 and microhardness from 743 Hv to 916 Hv. Finally, the hardness of all the light-weight HEAs (LWHEAs) with densities below 4.6 g/cm3 manufactured to date were reviewed. The hardness of Al40Cu15Cr15Fe15Si15 and hardness to density ratio of Al65Cu5Cr5Si15Mn5Ti5 are the highest of all LWHEAs reported up to date.