Jorge Malarria

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Papers by Jorge Malarria

Texture in Cu-based shape memory strips obtained by twin roll casting

by Raúl Bolmaro and Jorge Malarria

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008

Strips of Cu–13Al–5Ni–1Ti (wt.%) of about 400 μm thickness were obtained by twin-roll casting dir... more Strips of Cu–13Al–5Ni–1Ti (wt.%) of about 400 μm thickness were obtained by twin-roll casting directly from the melt. Temperature-induced transformations under constant tensile load show a larger deformation, associated with the reversible martensitic transformation, for strips annealed at 700 °C and 900 °C than for the as-cast samples. This effect is partially ascribed to relaxation of internal stresses produced by the rapid solidification, some recovery of short-range disorder and microstructural changes related to Ti-rich X-phase precipitates. On the other hand, the strips show a columnar grain morphology and annealing leads to an increase of texture intensity related with the increase in elongation rate. Columnar grains are mostly aligned with the 〈0 4 0〉R18//〈1 0 0〉DO3〈0 4 0〉R18//〈1 0 0〉DO3 directions.

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$Research paper thumbnail of Degradation of refractory bricks by hydration$

Degradation of refractory bricks by hydration

ABSTRACT

Preparation by Twin Roll Casting and Characterization of TiNi Shape Memory Alloys Strips

by Jorge Malarria and P. Vermaut

Solid State Phenomena, 2007

Study of atomic displacement fields in shape memory alloys by high-resolution electron microscopy

by Jorge Malarria and P. Vermaut

Materials Science and Engineering: A, 1999

ABSTRACT The distortion of the atomic lattice is determined using a recently developed method of ... more ABSTRACT The distortion of the atomic lattice is determined using a recently developed method of analysing high resolution electron microscope images. The analysis is carried out in terms of the individual lattice fringes which contribute to the image contrast. A perfect set of fringes has an amplitude and phase given by the corresponding Fourier component. A distorted lattice can be analysed by introducing the concept of a ‘local’ Fourier component, representing the local values of amplitude and phase as a function in position of the image. The local phase is used to determine the line of a perfectly coherent interface between two sets of lattice planes. The degree of self-accommodation of a series of martensitic plates in a Cu–Zn–Al shape-memory-alloy is studied by the phase analysis of an experimental high resolution image.

Texture in Cu-based shape memory strips obtained by twin roll casting

by Jorge Malarria and C. Sobrero

Materials Science and Engineering: A, 2008

Strips of Cu-13Al-5Ni-1Ti (wt.%) of about 400 m thickness were obtained by twin-roll casting dire... more Strips of Cu-13Al-5Ni-1Ti (wt.%) of about 400 m thickness were obtained by twin-roll casting directly from the melt. Temperature-induced transformations under constant tensile load show a larger deformation, associated with the reversible martensitic transformation, for strips annealed at 700 • C and 900 • C than for the as-cast samples. This effect is partially ascribed to relaxation of internal stresses produced by the rapid solidification, some recovery of short-range disorder and microstructural changes related to Ti-rich X-phase precipitates. On the other hand, the strips show a columnar grain morphology and annealing leads to an increase of texture intensity related with the increase in elongation rate. Columnar grains are mostly aligned with the 0 4 0 R18 // 1 0 0 DO 3 directions.

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Shape memory properties of Cu-based thin tapes obtained by rapid solidification methods

Materials Science and Engineering: A, 2006

Two different rapid solidification techniques were utilized to produce thin tapes of Cu-13Al-xNi-... more Two different rapid solidification techniques were utilized to produce thin tapes of Cu-13Al-xNi-1Ti (wt.%, with x = 5, 5.5, 6) shape memory alloys directly from the melt. Both melt-spinning and twin-roll casting (quenching between the gap of two rollers) have resulted successful methods to obtain ribbons (8 mm width, 55 m thickness) and strips (29-30 mm width, 450 m thickness) with grain sizes below 2 m, after optimization of the processing parameters. Although as a consequence of the rapid solidification the martensitic transformation temperatures are depressed, after annealing at 700 • C the high transition temperatures of the alloys in the bulk form are re-established. Measuring of length change under uniaxial tensile load shows elongations up to 1.8% (at 90 MPa) on cooling through the martensitic transformation.

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$Research paper thumbnail of Degradation of Magnesite-Chrome Refractory Brick by Hydration$

Degradation of Magnesite-Chrome Refractory Brick by Hydration

J Amer Ceram Soc, 2005

Magnesite-chrome refractory brick that is heated to temperatures as low as 500 C undergoes premat... more Magnesite-chrome refractory brick that is heated to temperatures as low as 500 C undergoes premature degradation, with a significant decrease in mechanical properties. Results that are obtained by dilatometry, differential thermal analysis, thermogravimetry, differential scanning calorimetry, X-ray diffractometry, and water absorption indicate that superficial hydration of the periclase grains during storage causes such degradation.

Microstructure and shape memory properties of Fe–15Mn–5Si–9Cr–5Ni melt-spun ribbons

Materials Science and Engineering: A, 2012

ABSTRACT At room temperature, conventionally formed Fe-15Mn-5Si-9Cr-5Ni alloys are normally auste... more ABSTRACT At room temperature, conventionally formed Fe-15Mn-5Si-9Cr-5Ni alloys are normally austenitic and the application of a stress induces a reversible martensitic transformation, causing a shape memory effect (SME). However, when the material is processed by a melt-spinning technique, the rapid solidification can stabilize the high-temperature ferritic phase. We found various austenite/ferrite structures in our melt-spun ribbons. The goals of this work were to correlate the process conditions with the resulting phases, find the appropriate heat treatment in order to recover the equilibrium austenitic phase, characterize the different ribbons formed from this material and evaluate the ribbons&#39; shape memory behaviour. We found that annealing at 1050 degrees C for 60 min, under a protective argon atmosphere, followed by water quenching, fully retains the austenite to room temperature. We compared particular ribbons, those originally austenitic, to the heat treated ones and analyzed the relationship between yield stress and microstructure and texture. The results from the shape memory tests demonstrate that the ribbons are capable of recovering enough of their shape for certain applications. (c) 2012 Elsevier B.V. All rights reserved.

Design of Devices and Manufacturing of Fe-Mn-Si Shape Memory Alloy Couplings

by Jorge Malarria and Ana Velia Druker

Procedia Materials Science, 2015

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Characterization of phases in an Fe–Mn–Si–Cr–Ni shape memory alloy processed by different thermomechanical methods

by Jorge Malarria, Ana Velia Druker, and Alberto Baruj

Materials Characterization, 2015

ABSTRACT

Optimization of Fe-15Mn-5Si-9Cr-5Ni Shape Memory Alloy for Pipes and Shafts Couplings

Journal of Materials Engineering and Performance

ABSTRACT We investigated whether Fe-Mn-Si shape memory alloys could be manufactured into machine ... more ABSTRACT We investigated whether Fe-Mn-Si shape memory alloys could be manufactured into machine parts and devices, in particular pipe and shaft couplings. Accounting for the optimal parameters affecting shape memory properties, i.e., the chemical composition, the amount of processing deformation, the annealing temperature, and the correlation between the reversibility of the martensitic transformation and the conditions of the microstructure (particularly the role of crystal defects), we found that maximum recovery in a Fe-15Mn-5Si-9Cr-5Ni alloy is achieved by rolling at 800 °C followed by annealing at 650 °C. Furthermore, we investigated certain properties that establish technological feasibility limits to industrial production, including alloy weldability and mechanical response. Bending and tensile specimen tests determinate the expected behavior of parts joined by welding. We also developed an original process to produce the couplings. The degree of shape recovery of the couplings manufactured by this method depends on the annealing temperature after welding. The couplings annealed at 800 °C recovered 83% of a 3.6% permanent diametrical expansion.

β-grainsize Effects on the 18R-martensite Microstructure in Cu-based SMA

by Jorge Malarria and P. Vermaut

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A critical feature in the Ag-sheathed Y-Ba-Cu-O wires sintering process

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Effect of lattice defects on shape memory properties of Fe-Mn-Si alloys

We have investigated two shape memory ferrous alloys, Fe-30Mn-4Si and Fe-15Mn-4Si-9Cr-5Ni, proces... more We have investigated two shape memory ferrous alloys, Fe-30Mn-4Si and Fe-15Mn-4Si-9Cr-5Ni, processed by different thermo-mechanical ways, in order to analyze the effect of processing conditions and the stacking fault energy values on their shape memory properties. Rolling was conducted at 20, 600-800 and 1000ºC, and afterwards the sheets were annealed between 650 and 1000ºC. The density and structure of dislocations, as well as the presence of stacking faults, strongly depend on the process temperatures. Among the investigated cases, the alloy containing 15% Mn, rolled at 800°C and annealed at 650°C, the recovery temperature, shows the best shape memory behavior.

Effect of the Manufacturing Process on the Texture and the Fraction of Stress-induced Martensite in an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

by Jorge Malarria, Ana Velia Druker, and V. Fuster

Fe-Mn-Si based alloys exhibit the shape memory effect (SME) through a γ(FCC) ↔ ɛ(HCP) stress-indu... more Fe-Mn-Si based alloys exhibit the shape memory effect (SME) through a γ(FCC) ↔ ɛ(HCP) stress-induced martensitic transformation. Studies carried out with single crystals have shown that the extent of shape recovery depends on the crystal orientation: it is nearly absent if the stress acts along the [001] direction and almost perfect when applied in the [414] direction. Therefore, certain crystallographic textures in polycrystals may contribute to better shape recovery with less applied stress. On the other hand, the texture is a consequence of the thermal and mechanical material processing history. This study analyzes how the particular forming process and the consequent texture development affects the amount of stress-induced ɛ martensite in an Fe-15Mn-5Si-9Cr-5Ni shape memory alloy. Besides determining the quantity of martensite produced, we measured the critical transformation temperatures and analyzed the effect of the manufacturing procedures on the SME properties.

Fatigue and the beta-18R martensitic transition in Cu-Zn-Al single crystals: mechanical behavior, defects and diffusive phenomena

The mechanical behavior during pseudoelastic cycling is one of the important properties of shape ... more The mechanical behavior during pseudoelastic cycling is one of the important properties of shape memory alloys. This presentation will focus its attention on Cu-Zn-Al single crystals. Several changes occur in this material during cycling by applying stresses at a constant temperature above Ms. Bulk defects consisting on dislocation bands with retained martensite and intrusion-extrusion surface defects are formed. The formation of the defects, density and other characteristics depend on the working temperature and alloy composition. In addition to this, the shape of the stress-strain curves are strongly affected by diffusive phenomena which take place in both phases involved, particularly above room temperature. Interaction of the atomic diffusion with the bulk defects has also been observed. The characteristics of all these processes must be known before a reliable simulation of the material behavior is performed. Controlled experiments where the kinetics of the diffusive phenomena ...

Bulk Defects in Pseudoelastically Cycled Cu-Zn-Al Single-Crystals

Journal de Physique IV, 1995

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Microstructure of Fe-14Mn-6Si-8Cr-5.5Ni ribbons obtained by rapid solidification

by Jorge Malarria and Ana Velia Druker

In Fe-Mn-Si alloys, the shape memory effect (SME) is related to a stress-induced martensitic tran... more In Fe-Mn-Si alloys, the shape memory effect (SME) is related to a stress-induced martensitic transformation. The transformation proceeds from the austenite phase, normally retained at room temperature, to a hexagonal-close-packed martensite: g (FCC) → e (HCP). However, when ribbons of a Fe-14Mn-6Si-8Cr-5.5Ni alloy are manufactured by rapid solidification, the high temperature ferritic phase can be retained. As a consequence, not only decreases the materials capacity to recover its shape, but weakens the material, as well. In melt-spinning techniques, the thickness of the ribbons as well as the stable or metastable phases that result from the process, depend mainly on the gas ejection pressure, liquid temperature, and wheel temperature and rotation speed. In this work, we used optical microscopy and transmission and scanning electron microscopy, to investigate the microstructures obtained for various melt-spinning process variables. We also analyzed the effect of heat treatments appl...

The Effect of Ageing and Annealing on Shape Memory Properties of Cu-Al-Ni Melt Spun Ribbons

by César Sobrero and Jorge Malarria

Acta Microscopica

Cu-13.5Al-5.5Ni-1Ti tapes with a grain refined microstructure of ~2 µm were obtained by melt spin... more Cu-13.5Al-5.5Ni-1Ti tapes with a grain refined microstructure of ~2 µm were obtained by melt spinning. The martensitic transformation temperatures of the precursor alloy were M s = 101°C, M f = 96°C, A s = 112°C, A f = 124°C. As result of the rapid solidification process, the transformation temperatures of this high temperature shape memory alloy shift below 0°C, and the melt spun ribbons are in the austenite phase at room temperature. Figure 1 shows the characteristic cell morphology of the austenite microstructure: The cells are clearly outlined by plates of martensite placed on their boundaries, corresponding mainly to the 18R orthorhombic structure although the 2H hexagonal structure was also observed. A high cooling rate causes a decreased order, reduced grain size, and an increased density of dislocations [1]. The concentration of quenched-in vacancies promotes more marked ageing phenomena in this melt spun alloys and the stability of the transformation temperature is an impor...

The effect of temperature on pseudoelastic cycling of CuZnAl single crystals

Scripta Metallurgica et Materialia, 1994

ABSTRACT

Jorge Malarria

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