This investigation deals with the effect of cooling rate on the formation of carbide nodular iron alloyed with 2.2 % Cr and equivalent carbon near 4.3%. In the experimental stage three Y-blocks of 1.5, 3 and 5.5 cm in thickness are poured in green sand molds. Castings are sectioned in two positions (wall and center samples) in order to determine the characteristics of the precipitated carbides (fraction, distribution and relative size) from surface to center and from the bottom to the top of the castings applying quantitative analysis of images. The obtained results show the presence of carbides in all of the castings. Finer carbides are obtained in the thinnest casting but with a high variation between the samples located in the wall and center. All castings present massive carbides in the last freezing zone (LFZ). Therefore the cooling rate associated with casting thick has an important effect on the fraction and distribution of carbides.

The effects of austenitizing temperature and cooling rate on the microstructures and textures produced by phase transformations in high strength hot rolled Fe-C-Mn steel plates are investigated using orientation imagining microscopy. Samples machined from the plates are austenitized at temperatures between 820-950°C during 30 minutes and quenched in either iced-water, water or oil. Finally, the quenched samples are tempered at 450°C during 30 minutes. Characterization of microstructure and textures produced by these heat treatments was performed by conventional metallography using a reflected light microscope and orientation imaging microscopy using backscattered-electron diffraction patterns in a scanning electron microscope with thermo-ionic electron source.

The results show that the microstructure and texture produced under a given combination of austenitizing temperature and cooling rate are strongly dependent on the mechanism involved in the phase transformation of the austenite (γ). High austenitizing temperatures and cooling rates promote martensitic transformation and development of textures containing significant volume fractions of Br, Cu, transformed-Cu and transformed-Br orientation components. In this case, the austenite and martensite phases are clearly related through the Kurdjumov-Sachs orientation relationship. In contrast, low temperatures and low cooling rates result in a complex mixture of transformation products, such as polygonal ferrite, Widmanstäten ferrite, martensite, bainite and pearlite. The textures formed under these conditions are quite different and contain significant volume fractions of cube, rotated-cube, Goss and rotated-Goss components, following the Bain orientation relationship.

Thermotropic polymers are thermally treated in air at temperatures Ta, where ΔT =Ta- Ts→n=40°C, and Ts→n is the solid-to-nematic transition. Samples are extruded thin films of a series of thermotropic random copolyesters termed B-N, COTBP and RD1000. The thermal treatment produces a second endotherm without changing Ts→n for B-N and RD1000. However, for COTBP Ts→n is significantly increased. Regardless of the complex thermal behavior exhibited by the thermotropes, the thermal treatment produces a significant increase in Young's modulus, more than 30% for B-N and over 100% for COTBP. The increase in mechanical modulus is correlated with a thermally-induced fiber-like morphology.

This research work studies the dynamically recrystallized austenitic grain size (Drec) in a new family of low carbon NiCrCuV advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions. For this purpose, uniaxial hot-compression tests are carried out in a low carbon A-UHSS microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) over a wide range of temperatures (950, 1000, 1050 and 1100°C) and constant true strain rates (10−3, 10−2 and 10−1 s−1). Deformed samples are prepared and chemically etched with a saturated aqueous picric acid solution at 80°C in order to reveal the Drec and examined by light optical (LOM) and scanning electron microscopy (SEM). The Drec is related to the Zener-Hollomon parameter (Z), and thereafter the Drec divided by Burger's vector (b) is related to the steady state stress (σss) divided by the shear modulus (µ) (Derby model). Results shown that the Drec in the current steels is fine (≈ 23 μm) and almost equiaxed, and the recrystallized grain size-flow stress relationship observed after of plastic deformation is consistent with the general formulation proposed by Derby. It is corroborated that boron additions to the current A-UHSS do not have meaningful influence on the Drec.

The kinetic arrest of martensitic transformation (MT) has been observed in as-solidified Ni52.2Mn34.3In13.5 melt spun ribbons. The main characteristics of this unusual field-induced magneto-structural phenomenon have been determined through a dc magnetization study. The sample studied was fabricated by rapid solidification using the melt spinning technique at a high quenching rate of 48 ms-1. At room temperature, it is a single phase austenite (AST) with the bcc B2-type crystal structure and Curie temperature of TCA=285 K. With decreasing temperature, the austenite phase transforms into the martensite phase (MST) with TCM≈185 K at a starting martensitic transition temperature of MS=275 K. A moderate but progressive kinetic arrest of the AST to MST transformation has been observed for magnetic field values above H=10 kOe and was studied up to Hmax= 90 kOe. The metastable character of the non-equilibrium field-cooled state is revealed by the decreasing behavior of the saturation magnetization under a large magnetic field of 50 kOe after temperature cycling from 10 K to 150 K. The total magnetization difference Δσ between the zero field-cooling and field-cooling pathways of the temperature dependence of magnetization shows irreversible and reversible components and the former decreases with decreasing temperature.

The glass transition temperature Tg, crystallization temperature Tx, solidus temperature Tm, and liquidus temperature Tl, of a number of ternary Cu-Hf-Ti glassy alloys in the composition range of 51< Cu <67, 5 < Hf < 40 and 5 < Ti <40 (at.%) are reported and discussed. It is found that increasing the Ti:Hf ratio results in a rapid decreasing of Tg and Tx. This behavior is related to the fact that the melting point and cohesive energy for Ti are substantially lower than for Hf. The solidus temperature Tm, remains relatively constant on a wide range of compositions. The liquidus temperatures data suggest a ternary eutectic within the compositional field encompassed by the Cu55Hf20Ti25, Cu59Hf21Ti20, Cu60Hf20Ti20 and Cu55Hf21Ti24 alloys, with a liquidus temperature, Tl, of ∼1170 K; this is supported by the DTA traces, which show a single melting peak. Based on the DTA analysis, the experimentally calculated liquidus projection for the ternary Cu-Hf-Ti alloy system is also reported.

The purpose of this work is to compare the results obtained from three methodologies intended to estimate kinetic parameters describing quantitatively the grain growth during equiaxed eutectic solidification in order to identify the best procedure to characterize grain growth kinetics. A heat transfer / solidification kinetics model is implemented to simulate the cooling and solidification of eutectic Al-Si and eutectic cast iron in sand molds. Using simulated cooling curves and volume grain density data generated by the model, the three methods are applied to obtain their predicted grain growth coefficients. The predicted results are compared with the grain growth coefficients used in the model. The outcome of this work suggests that two of the three methods under study represent the best option to obtain the kinetic parameters of equiaxed growth during eutectic solidification.