Processing Smart Wires from Cu-Al-Ni System

In this paper we present some results concerning plastic deformation applied to shape memory alloy and two most direct characterization methods for shape memory. We work with a copper based alloy- Cu Al13Ni 4. Over eight percent in aluminum the plastic deformation on the copper aluminum alloys is very difficult to do. Our purpose was to obtain the thin wires. The first material shape was cast ingots very fragile. We choose to work with a direct extrusion method because the high fragility of this material required a three dimensional stress compression scheme

Effects of Plastic Deformation and Temperature on Microstructural and Mechanical Properties of a Cu Al Ni Shape Memory Alloy

In Cu 12.88% wt.Al4 %wt. Ni shape memory alloy the influence of plastic deformation and thermal treatments on the microstructures and hardness were studied by optical microscopy, scanning electron microscopy (SEM), Vickers Hardness. The plastic deformation on the austenite (b) was studied at temperatures T>Md when transformation can occur with no stress or strain induced condition. Lattice defects were introduced into stable austenite of a Cu Al Ni alloy by a hot rolling, in one pass, and subsequent quenching after leaving the rolling cylinders. From microstructural observations it has been seen that two b1’(18R) and g1’(2H) martensite phases coexists at different fractions in the undeformed and deformed states. Plastic deformation causes change in the relative amounts of b1’and g1’ martensites with a new morphology. The finest martensite structure has been obtained by thermo-mechanical treatment. The hardness test highlights the influence of treatments tightly correlated with the structures obtained

Microstructural Evolution of Al 1100 Aluminum Subjected to Severe Plastic Deformation

The goal of this document is to promote a sequence of bulk-deformation processes able to produce ultrafine grain and also nanostructured wires with adequate length to be interesting for processing in metallurgical industry. Samples of aluminum Al 1100alloy (98.41 % Al) were subjected to repetitive Equal Channel Angular Pressing at room temperature in 1 to 4 passes. Severe deformed specimens were cold classical plastic deformed in wires. Microstructural evolution and mechanical properties were investigated. Optical microscopy progression is evaluated through a sequential interrupted process on each separate ECAP pass. The XRD studies reveal the influence of SPD on grain refinement of samples. A simply and new technology for obtaining intermediary products UFG and nanocristalline wires was developed

Evolution of Copper Microstructure Subjected to Equal Channel Angular Pressing

This paper aims to study bulk severe plastic deformation processes capable to produce ultrafine grain and also nanostructured 3D materials, interesting for processing in current industry. Samples of copper alloy were solution treated and then were subjected to repetitive Equal Channel Angular Pressing at room temperature in 1 to 8 passes, using route C. Severely deformed specimens were studied after each deformation pass. Their microstructural evolution and mechanical properties were investigated. Optical microscopy progression is evaluated on each separate ECAP pass. It is well known that although copper is a deficient resource it is used to the same extent as aluminum, a rich resource on the earth’s crust. This research signs up in the category of new technologies for obtaining bulk metallic nanostructures that allow more judicious use of copper alloys by the substantial improvement of properties of use

Severe Plastic Deformed Pure Aluminum by Equal Channel Angular Pressing

Samples of an aluminum alloy were subjected to an equal channel angular pressing (ECAP) at room temperature for one pass. For the several specimens severe plastic deformation process was interrupted to observe the material flow. Also are studied the force variation in SPD process and hardness in different zones of the deformed sample

Kinetic of Martensite Transformation in a Cu-13wt.%Al-4 wt.%Ni Shape Memory Alloy

In this paper we present some results was obtained on the Cu-13 wt.%Al-4 wt.%Ni shape memory alloy. This alloy was elaborated by a classic melting method starting at pure metals. A DSC analysis was made for quenched sample cut from 4 mm diameter hot extruded wires. The results confirm thermoelastic transformation and provide for further application the critical temperatures for martensitic transformation

The Johnson-Mehl-Avrami Model Applied to Martensitic Kinetics in Ausformed Cooper Based Shape Memory Alloy

CuAlNi shape memory alloys which are used as sensors and actuators have also been investigated recently as materials for medicine devices. This study shows the influence of the thermo – mechanical treatments in CuAl13Ni4 shape memory alloy on martensitic transformation kinetics and microstructures. While maintaining a constant 20% degree of deformation, deformation temperature was varied between 800 oC and 1000 oC. The alloy was investigated by differential scanning Calorimetry (DSC) and optical microscopy. The validity of JMA model to the kinetics analysis was checked. The changes in the microstructure and kinetic transformations have been linked to the evolution of the rolling temperature that introduced high density dislocations in initial phase and changes fraction and interaction between the β1’ (18R) and γ1’ (2H) martensite coexisting in this shape memory alloy

Severe Plastic Deformation an Advanced Method for Nanostructuring Shape Memory Alloys

Severe plastic deformation (SPD) is an advanced plastic deformation. In this process nanostructuring metals and alloys may be produced. Nanostructured shape memory alloys are associate with a very high strength, toughness, fatigue life and wear resistance. In recent, bulk nanostructured SMA are used for medicine advanced applications and smart micro devices. In this paper we present the concept and principles SPD. There are two distinct methods: Equal Channel Angular Pressing ECAP or Equal Cannel Angular Extrusion –ECAE and High Pressure Torsion – HPT. Also we present some results about nanostructuring a hard deformable shape memory alloy using a original HPT, and a improved ECAE device

Two-way Shape Memory Effect in a Cu-13 wt.%Al-4 wt.%Ni Shape Memory Alloy by the Thermo - Mechanical Cycling Method

A Cu - 13 %wt Al 4 %wt Ni polycrystalline shape memory alloy has studied with a thermo mechanical cycling method. The two – way shape memory effect (TWSME) was obtained bending the alloy around a cylinder mold and by using a constrained heating – cooling technique. This alloy elaborated by a classic melting method was extruded in wires with 4 mm diameter and was hot rolled in sheets with thickness

X-Ray Diffraction Study of the Reverse Martensitic Transformation In Cu-Al-Ni Shape Memory Alloy

The paper presents an X ray diffraction study for a cooper based shape memory alloy. The behavior of CuAl13Ni4 alloy, which exhibits a peculiar property, is evaluated by structural changes. On cooling, the martensitic transformation takes place from the ordered structures to the long period two layered structure. The crystalline phase transformations of those alloys are very sensitive to the heat treatments, deformation degrees and also to the undesired aging effects. In particular, the study has been made on the CuAl13Ni4 shape memory alloy samples after being hot extruded, quenched and aged in martensitic state