The Microstructure and the Phase Stability of a Cu–30at.%Al Alloy Obtained by Reactive Milling and Quenching

The phase stability of a Cu–30at.%Al milled and quenched is studied by differential scanning calorimetry and in situ high-temperature X-ray diffraction (HT-XRD). This analysis was performed from room temperature to 700 °C. The grain growth at fixed temperatures was analyzed by HT-XRD. The size of the γ2 phase grains do not change at a constant temperature with the time at temperatures below 600 °C. This behavior was attributed to the pulling force resulting from the presence of nanometric grains. The presence of nanometric grains was confirmed by TEM. The lack of grain size growth at a constant temperature is a promising result for the technological application of the Cu–30at.%Al milled and quenched as a shape memory alloy.Fil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Esquivel, Marcelo Ricardo Oscar. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Zelaya, Maria Eugenia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin

Study of the formation of Cu-24at.% Al by reactive milling

In this work, powders of Cu and Al were milled with a proportion equal to 24 atomic % Al, using low and medium energy mills. The initial, intermediate and final stages of the resulting powder are analyzed using scanning electron microscopy, X-ray diffraction and different transmission electron microscopy techniques. The structure and microstructure achieved in each step of the milling process are compared to the results of Cu-16at.%Al and Cu-30at.%Al obtained under the same conditions of reactive milling. At the final stage of milling, it was detected that the obtained intermetallic is not the equilibrium phase of the Cu-Al system.Fil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Muñoz Vásquez, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Garro González, M.. Universidad de Costa Rica; Costa RicaFil: Esquivel, Marcelo Ricardo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Zelaya, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Effects of Strain Rate on the TRIP–TWIP Transition of an Austenitic Fe-18Mn-2Si-2Al Steel

A fully austenitic Fe-18Mn-2Si-2Al transformation-induced plasticity (TRIP) steel was tensile tested from quasi-static to low-dynamic regime at three different strain rates: 4.7 × 10−4, 1.3 × 10−1, and 8.3 × 100 s−1. Typical two-stage transformation mechanism, TRIP γ → ε → α′, was observed for samples tested at 4.7 × 10−4 s−1. At higher strain rates, the increase in temperature due to adiabatic plastic work shifts the stacking fault energy (SFE) towards a twinning-induced plasticity–SFE-range modifying the mechanical behavior of the alloy. This change on the deformation mechanism leads to a lower work hardening capacity and a higher elongation to rupture in samples tested at 1.3 × 10−1 and 8.3 × 100 s−1. In this context, the alloy maintains its energy absorption capability with a maximum reduction of 3.6 pct according to the Rm × A parameter. The Md temperature, experimentally determined in the present study, proved to be a useful tool for understanding the material’s behavior.Fil: Raposo, Marcio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Martín, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fuster, Valeria de Los Angeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Malarria, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Effect of the precipitates on the thermodynamics of the martensitic transformations in Ti-rich Ni-Ti-Co thin films

The wide-spread multiple transformation in Ti-rich Ni-Ti shape memory alloys produced by Ti2Ni nano-precipitates was investigated. For this purpose, a series of amorphous Ti-Ni-Co thin films with the same composition were subjected to different annealing treatments. The characteristic temperatures and heat of the transformations were measured by four-point probe resistivity and differential scanning calorimetry. A critical review of the thermodynamics of thermally-induced thermoelastic martensitic transformations is presented. The values of the frictional work and the stored elastic energy associated with the thermoelastic transformations were assessed from the transformation temperatures, and related with the transformation heats measured in the samples annealed at different temperatures. It was observed that the stored elastic energy decreases as the annealing temperature rises due to a change in the distribution of the Ti2Ni precipitates, in concordance with an increase of the transformation heat measured by the calorimeter. Nevertheless, the values of the frictional work were independent of the annealing temperature. The influence of the dissipation of the stored elastic energy on the transformation temperatures and thermal hysteresis is discussed. Finally, a better understanding of the wide-spread multiple transformation, as an effect of the local stresses introduced by Ti2Ni nano-precipitates in the matrix, is proposed.Fil: Isola, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Malvasio, Bruno Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Malarria, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

A detailed study of phase evolution in Cu-16 at. %Al and Cu-30 at. %Al alloys under different types of mechanical alloying processes

The phase stability of Cu-16 at. %Al and Cu-30 at. %Al alloys obtained by a planetary and an horizontal mills was investigated. The analysis was carried out using X-ray diffraction and various transmission electron microscopy (TEM) techniques. X-ray diffraction analysis gives a statistical overview of the main equilibrium phases present. Meanwhile, the different TEM techniques allow the detection of either the minor phases or the ones having crystalline domains smaller than 5 nm. The solid solution equilibrium α phase was obtained using both milling processes on the Cu-16 at. %Al. Instead, the final intermetallics observed for Cu-30 at. %Al were not the equilibrium ones according to the phase diagram. The planetary mill produced a mixture of α and γ2 phases and less than a 2 at. % of β phase. The horizontal mill produced a γ2 phase and less than a 2 at. % of α2 and γÍ phases. For both compositions, the horizontal mill seems to be more efficient to achieved the equilibrium intermetallic compound.Fil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Esquivel, Marcelo Ricardo Oscar. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; ArgentinaFil: Zelaya, Maria Eugenia. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentin

Cyclic Deformation and Microstructural Behavior of Reduced Activation Ferritic-Martensitic Steels

The present paper presents results about cyclic behaviour and the evolution of the dislocation structure of reduced activation ferritic–martensitic steels and commercial martensitic steels AISI 410 and 420. The variation of the free dislocation density within subgrains and subgrain size was mainly analysed during the cyclic softening of EUROFER 97 steel. From the analysis of the flow stress components, the friction and back stresses, and the information of the evolution of the dislocation structure, it could be concluded that the softening of tempered martensitic steels at 20°C is produced by the contribution of the friction stress and aided later by the back stress.Fil: Batista, Maria Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Hereñu, Silvina Andrea Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Alvarez, Iris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentin

Excellent pseudoelasticity of Al-rich Fe–33Mn–17Al–6Ni–0.15C (at%) shape memory single crystals obtained without an aging conditioning stage

The pseudoelastic behavior of a series of Fe?33Mn?17Al?6Ni?0.15C (at%) shape memory alloy single crys- tals was analysed with compression tests. The specimens, with different crystallographic orientations, showed almost 100% strain recovery after a full stress-induced martensitic transformation. The size and distribution of precipitates introduced in the alloy processing proved to be clearly suitable for achieving a completely reversible pseudoelastic transformation, without the need of additional aging in this Al-rich alloy. The transformation strain was analysed using the phenomenological theory of martensite transfor- mation. This model roughly describes the pseudoelastic strain under compression as a function of the crystallographic orientation.Fil: Vallejos, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Sobrero, Cesar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Malarria, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; Argentin

Analysis of the Cu-Al Milling Stages Through the Microstructure Evolution Studied by TEM and SEM

Mechanical alloying of Cu-16 at.%Al and Cu-30 at.%Al was performed using both a planetary and a horizontal milling devices. The starting powders were high-purity Cu and Al. The different stages of milling were identified and characterized as initial, intermediate, final, and completion. The obtained microstructures were investigated by scanning electron microscopy and transmission electron microscopy. The evolution of the microstructure was studied considering the particle size variation. A decrease in the particle size was found as the Al content increases. The evolution of the nanostructure was studied considering the grain size variation. No marked changes on the nanostructure were detected during milling regardless either the type of mill used or composition selected. Mean grain sizes’ values found were between 10 nm and 26 nm for each stage of milling. Power consumption of the milling process was calculated at laboratory scale to analyze the chances of a potential scaling up of the milling process. Starting aggregation state, microstructure and dominant phase changes, and evolution of mechanical alloying stages were considered. Performance of milling was compared to traditional high-temperature methods to compare the advantages and disadvantages of both synthesis methods.Fil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Muñoz Vásquez, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Esquivel, Marcelo Ricardo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Zelaya, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Cyclic Superelastic Behavior of Iron-Based Fe-Ni-Co-Al-Ti-Nb Shape Memory Alloy

Iron-based shape memory alloys came into focus as promising candidate materials for large-scale structural applications owing to their cost-efficiency. In the present work, the superelastic properties of a recently introduced Fe-Ni-Co-Al-Ti-Nb shape memory alloy are investigated. For 〈001〉-oriented single-crystalline material in aged condition (650 °C/6 h), an incremental strain test reveals excellent superelasticity at −130 °C with fully reversible strains up to about 6%. Under cycling loading at different test temperatures, however, the alloy system investigated suffers limited functional stability.Fil: Lauhoff, C.. University of Kassel; AlemaniaFil: Remich, V.. University of Kassel; AlemaniaFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Sobrero, Cesar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Niendorf, T.. University of Kassel; AlemaniaFil: Krooß, P.. University of Kassel; Alemani

Pearlite Development in Commercial Hadfield Steel by Means of Isothermal Reactions

The Fe–12Mn–1C Hadfield steel is an abrasion-resistant alloy of high technological relevance for mining and heavy machinery. This composition is susceptible to pearlite formation which is detrimental for the material’s ductility. Although its spread use, the study of pearlite formation has been preserved to laboratory conditions which cannot be transferred to industrial practices. This manuscript provides updated information about this phenomenon by constructing the time–temperature-transformation diagram of the alloy between 400 and 600 °C. The pearlitic reaction occurs above 450 °C and begins on the grain boundaries. Only 7 min is needed for the transformation to start at 550 °C, and a maximum pearlite fraction of 35% is reached after 150 min at this temperature. Results are compared with the Fe–12Mn–0.8C composition mostly found in literature. The discussion comprises the effects of carbon and manganese content on the pearlitic reaction with the support of thermodynamics calculations.Fil: Martín, Mauro Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Raposo, Marcio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Prat, O.. Universidad de Concepción; ChileFil: Giordana, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Malarria, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin