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Effect of C and Mn Variations Upon the Solidification Mode and Surface Cracking Susceptibility of Peritectic Steels

José Jorge Ruiz Mondragon (2009)

This work studies the effect of chemical composition, C and Mn contents, and cooling rate on both the solidification mode and the evolution of phases during the solidification of three steels; two of hypo-peritectic and one of hyper-peritectic composition. Furthermore, the cracking susceptibility associated to both the differences in mechanical behavior of d and g phases, and contraction during solidification, was inferred. Slight variation of C or Mn, in the order of 0.04%, promoted significant changes in the evolution of phases during solidification. It was observed that for the hypo-peritectic steel closer to the peritectic point, the Mn microsegregation observed for high cooling rates promoted at the end of solidification a hyper-peritectic solidification mode. On the other hand, independently of the solidification mode and chemical composition of the studied steels, the differences in the mechanical behavior of d and g phases led to a cracking susceptibility in two solid fraction zones. Furthermore, for the steel exhibiting hypo-peritectic solidification mode the peritectic transformation occurred at higher solid fraction compared with the steels showing hyper-peritectic solidification mode. Therefore, the remaining liquid ability to feed the contraction in the solid–liquid shell associated to the peritectic transformation resulted adversely affected. Hence, the cracking susceptibility observed in the hypo-peritectic steel is not only generated by differences in the mechanical behavior of d and g phases, but also by the liquid inability to compensate the contraction associated to the peritectic transformation.

Article

SOLIDIFICACIÓN INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS CIENCIAS TECNOLÓGICAS

Solidificación direccional de aleaciones Fe-Cr-C con adiciones de boro y su evaluación bajo condiciones de desgaste

Ricardo Correa Terrazas (2011)

Instituto de Investigaciones Metalúrgicas. Doctorado en Ciencias en Metalurgia y Ciencias de los Materiales

In this research the effect of additions of boron (less than 195 ppm) in a high chromium white iron (17% Cr-2.5% C) directionally solidified analyzed. Due to the high level of segregation during solidification having a constitutional boron overcooling in austenite amending the solidification rate of the leading sub-phase (austenite) is generated, so that a change occurs solidification mechanism accompanied by a refinement of the microstructure of the iron. Microanalysis composition were performed using a scanning electron microscope, determining the chemical distribution within the phases forming the microstructure, where it was observed that the boron segregates to the austenite / carbide interface and this is mainly dissolved in the eutectic carbide, some sometimes forming a boron compound.

En esta investigación se analiza el efecto de adiciones de boro (menores a 195 ppm) en un hierro blanco alto cromo (17% Cr-2.5% C) solidificado direccionalmente. Debido al alto nivel de segregación durante la solidificación que presenta el boro se genera un sobre-enfriamiento constitucional en la austenita que modifica la velocidad de solidificación de la fase sub-líder (austenita), por lo que se presenta un cambio el mecanismo de solidificación, acompañado de un refinamiento de la microestructura del hierro. Se realizaron microanálisis de composición usando un microscopio electrónico de barrido, determinando la distribución química dentro de las fases que forman la microestructura, donde se observó que el boro segrega hacia la interfase austenita/carburo y este se encuentra principalmente disuelto en el carburo eutéctico, algunas veces formando un compuesto de boro.

Doctoral thesis

INGENIERÍA Y TECNOLOGÍA IIM-D-2011-0001 Solidificación Aleación Boro

Efecto magnetocalórico en cintas de los compuestos intermetálicos RNi2 (R= Tb, Dy, Ho, Er) y RAl2 (R= Tb, Dy, Er) obtenidas por solidificación rápida

Pablos Jesús Ibarra Gaytán (2017)

"Varios compuestos intemetálicos en los sistemas binarios RNi2 y RAl2 (R= tierra rara) presentan buenas propiedades magnetocalóricas en el rango de temperatura entre 10 y 80 K, lo que permite su utilización como sustancias refrigerantes para el desarrollo de sistemas de refrigeración para la licuefacción de gases. En el presente trabajo se reporta la obtención y la caracterización de las propiedades magnetocalóricas de los compuestos intermetálicos RNi2 con R= Tb, Dy, Ho, Er, y RAl2 con R= Tb, Dy, Er. Los mismos fueron sintetizados por solidificación rápida usando la técnica de temple rotatorio. Se reportan las curvas de variación de entropía magnética ?SM(T) y variación de temperatura adiabática ?Tad(T), así como la capacidad de refrigeración RC para variaciones de campo magnético ?o?H de 2 y 5 T. Estas se comparan con resultados experimentales y teóricos reportados por otros autores en la literatura para muestras policristalinas en bulto. Se determina el compósito bifásico magnetocalórico con mejores propiedades basado en los compuestos DyNi2 y TbNi2 (0.4(DyNi2) + 0.6(TbNi2)). Los compuestos sintetizados son policristalinos y cristalizan en una estructura cúbica de tipo MgCu2 (C15) propia de las fases de Laves; los parámetros de celda así como la temperatura de Curie son similares a los reportados para muestra en bulto. Las cintas recién solidificadas de los compuestos DyNi2, HoNi2 y ErNi2 presentaron valores superiores de |?SMpeak| según la dirección longitudinal con respecto a lo reportado para aleaciones policristalinas en bulto. Esto resulta de la combinación de la anisotropía de la magnetización que presentan estos materiales con la textura cristalográfica que se obtiene como resultado de la técnica de síntesis empleada. En estos casos, las cintas están formadas por granos con su eje principal de crecimiento perpendicular al plano de las cintas por lo que el eje de fácil magnetización queda con cierta orientación preferencial según la dirección longitudinal de formación de la cinta."

"Several intermetallic compounds in the RNi2 and RAl2 binary systems (R= rare earth), shows good MC properties as magnetic refrigerants in the temperature range 10-80 K; this allows their use as magnetic refrigerants for the development of magnetic refrigerators for gases liquefaction. Present work, focuses on the synthesis and characterization of the magnetocaloric properties of the intermetallic compounds RNi2 with R= Tb, Dy, Ho, Er, and RAl2 with R= Tb, Dy, Er. They were synthesized by rapid solidification using the melt spinning technique. The thermal dependence of the magnetic entropy change ?SM(T) and adiabatic temperature change ?Tad(T) curves, as well as the refrigerant capacity (RC) for magnetic field changes ?o?Hmax of 2 and 5 T are reported. They are compared with the theoretical and experimental results reported for bulk polycrystalline samples in literature by other authors. The two-phase composite with the best magnetocaloric properties based on the DyNi2 and TbNi2 compounds is (0.4(DyNi2) + 0.6(TbNi2)) is reported. The melt-spun ribbons of the compounds produced are polycrystalline and crystallize into the cubic MgCu2-type structure (C15) of the Laves phases; the cell parameters and the Curie temperature are similar to those reported for bulk polycrystalline alloys. For as-solidified ribbons of the DyNi2, HoNi2 and ErNi2 compounds we found showed superior |?SMpeak| values with respect to the reported for bulk polycrystalline alloys along the longitudinal direction. This enhanced MC response along ribbon longitudinal direction results from the combination of the distinct anisotropic magnetization of these materials with the crystallographic texture induced by the fabrication method employed. In these cases, the ribbons are formed by columnar in shape grains with their longer axes perpendicular to ribbon plane; then the easy axis magnetization shows preferential orientation along the rolling direction."

Doctoral thesis

Compuesto intermetálico Efecto magnetocalórico RNi2 RAl2 Solidificación rápida CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA FÍSICA

Effect of Solidification Path and Contraction on the Cracking Susceptibility of Carbon Peritectic Steels

José Jorge Ruiz Mondragon (2010)

The solidification path and contraction generating during the solidification of three carbon steels were studied. Two of the carbon steels were of hypo-peritectic chemical composition, with 0.11 % C and 0.15% C, while one of the carbon steels were hyper-peritectic with 0.16% C.

Article

SOLIDIFICACIÓN, PROPIEDADES MECÁNICAS INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS CIENCIAS TECNOLÓGICAS

Description of the Hypo-peritectic Steel Solidification under Continuous Cooling and Crack Susceptibility

José Jorge Ruiz Mondragon (2008)

This study describes the phase evolution during solidification under continuous cooling conditions of a hypo-peritectic multicomponent steel. Additionally, the mechanical behavior and dimensional variation of the solid–liquid skin were evaluated by using mathematical expressions reported in the literature as a function of the proportion of phases and solute distribution respectively. The crack susceptibility of the solid–liquid skin depended on the proportion of phases and it occurred in two solid fraction regions, independently of the cooling rate. For the region exhibiting the lowest solid fraction values this susceptibility was associated to g phase, while at the highest solid fraction values it was related to d phase. At the end of the peritectic transformation the highest contraction observed can be considered as an additional contribution to the crack susceptibility in the solid fraction range of 0.92–0.98. The significant microsegregation of Mn observed for high cooling rates promotes a change in the solidification mode, from a hypo-peritectic mode into a hyper-peritectic mode and the expansion of solid formed from the remaining liquid.

Article

solidificación; propiedades mecánicas INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS CIENCIAS TECNOLÓGICAS

Star cracks in continuously cast peritectic steel slabs

José Jorge Ruiz Mondragon (2010)

This work consisted of the characterisation of star cracks found on the surface of continuously cast steel slabs solidification experiments on molten steel in Cu moulds, with and without ceramic insulation. Cracks located at the slab surface were propagated through the grain boundaries, with the presence of Cu particles observed along the crack paths. Zones normal to the cracks exhibited an iron oxide layer followed by Cu particles and the steel matrix. Specimens solidified in Cu moulds showed an iron oxide/Cu/steel layer arrangement extending from the sample surface towards the steel matrix, as well as a penetration of Cu through the grain boundaries. In contrast, in samples solidified in ceramic insulated Cu moulds, Cu particles were neither observed at the surface nor at the grain boundaries. Thus, it is thought that the star cracks are due to liquid steel/ Cu mould interaction during casting and that they are formed during primary cooling in the mould in the continuous casting machine and then they propagate during secondary cooling and bending operations. It is also thought that cracking susceptibility is promoted by peritectic transformation which occurs at high solid fractions.

Article

SOLIDIFICACIÓN, STAR CRACKS INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS CIENCIAS TECNOLÓGICAS

EFFECT OF COOLING RATE DURING SOLIDIFICATION ON THE HARD PHASES OF M23C6-TYPE OF CAST CoCrMo ALLOY

MELVYN ALVAREZ VERA ALEJANDRA HERNANDEZ RODRIGUEZ (2016)

Microstructural morphology of CoCrMo alloy by control of the cooling rate during the solidification was investigated.

Samples were obtained using both an induction furnace for slow cooling rate and electric arc furnace for fast

cooling rate. Microstructural characterizations were performed with metallographic techniques. It was found that

the difference between the formation temperature of hard secondary phases of M23C6-type carbides determine the

reduction of carbide size by increasing the cooling rate.

Article

efecto de la tasa de enfriamiento en la solidificación de aleaciones de aluminio INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS

Sintesis y caracterización estructural y magnética de aleaciones y cintas de Ni-Ga-Fe

LAURA KARINA MIRELES NUÑEZ (2012)

"Algunas aleaciones tipo Ni-Fe-Ga con contenidos de hierro cercanos al 20% y níquel en un 54 % atómico, presentan una coincidencia entre la temperatura de transición magnética y la martensítica. Esta característica produce un aumento en el cambio de entropía alrededor de las transiciones. El cambio de entropía está relacionado directamente con la capacidad de refrigeración por efecto magnetocalórico. Esto hace interesante estudiar la microestructura y propiedades de tales aleaciones. Se presenta el estudio de la síntesis y caracterización de aleaciones ferromagnéticas con memoria de forma del sistema Ni-Fe-Ga. Se sintetizaron dos aleaciones de cada una de las composiciones Ni54.4Fe19Ga26.6 y Ni53.6Fe14.9Ga31.5. Se realizaron dos tratamientos diferentes para la misma composición, T1 (6h a 1000°C y 1h a 500°C y templado en agua a 20°C) y T2 (24 h a 1000°C, 1h a 500°C y templado en agua a 0°C). Se elaboraron cintas por la técnica de melt spining de cada una de las aleaciones. Las aleaciones fueron caracterizadas por Calorimetría Diferencial de Barrido, Microscopía Electrónica de Barrido, Espectroscopía de Dispersión de Energía, Difracción de Rayos X y Magnetometría de Gradiente de Campo Alterno. Se encontró que las aleaciones con composición cercana a 16% de hierro se obtienen monofásicas. Asimismo las aleaciones con 19% Fe mostraron fase gamma. El aumento en el tiempo de tratamiento térmico de homogenización logró una disminución en la proporción de fase gamma. La magnetización máxima observada aumenta con el contenido de hierro. En base a los resultados de la caracterización magnética realizada en las aleaciones con fase gamma, se consideró que esta fase tiene comportamiento antiferromagnético. Las cintas que presentaran un comportamiento paramagnético, se consideró que es debido a el enfriamiento no fue tan rápido y la aleación no alcanzó a ordenarse químicamente hasta L21. "

"Some alloys of the Ni-Fe-Ga system of composition close to 20 atomic % of iron and 54 atomic % of Ni show a concomitant effect of martensitic and magnetic transition. Such characteristic produces a higher entropy change around those transitions. The entropy change is associated to the relative cooling power provided by magnetocaloric effect. This fact makes interesting to carry out the microstructure and magnetic properties of such alloy. A study of the synthesis and characterization of shape memory alloys of the Ni-Ga-Fe system is presented in this job, when two alloys each compositions Ni54.4Fe19Ga26.6 and Ni53.6Fe14.9Ga31.5 were synthesized. Two different thermal treatments were carried out to one alloy of each composition: T1 (6 hours at 1000°C, 1 hour at 500°C and tempered in water at room temperature) and T2 (24 hours at 1000°C and 1 hour at 500°C and tempered in water at 0°C). Ribbons of alloys were made for each alloy using the melt spinning technique. Alloys were characterized using Scanning Electron Microscope, Energy Dispersive Spectroscope, X Ray Diffraction, and Alternative Gradient Field Magnetometer. Alloys with composition around 16%Fe were found have show a single phase microstructure of martensite. Likewise, alloys with 19% Fe have shown two phase microstructure (gamma phase and martensite). The increase in the thermal homogenization treatment time resulted in a decrease in the gamma phase ratio. The maximum observed magnetization increases with the iron content. Based on the results of the magnetic characterization performed on the gamma phase alloys, it has been considered that this phase presents antiferromagnetic behavior. The as quenched ribbons showed quasi-paramagnetic behavior, probably because while cooling, alloy goes through austenitic temperatures and cannot reach the L21 ordered structure."

Master thesis

Solidificacion rapida Trasformación martensintetica Aleacciones ferromagneticas con memoria de forma Ni-fe-Ga CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA