The microstructural evolution of the CuZnAl shape memory alloys was studied by indirect techniques relating to the atomic migration rate of grain boundaries. Addition elements were used in a Cu-15,5Zn-8,0Al alloy to provide a comparison with the same alloy without microelement additions. The alloys were melted in an induction furnace of 24 kVA. After casting, the bulk samples of the alloys were homogenized. Then they were solution treated and hot-rolled followed by water-quenching to initiate the recrystallization. Finally, annealing produced at different temperature ranges was made in different samples in order to establish a law for the grain growth. Following the heat treatments, all annealed samples were examined by statistical metallography and the grain sizes were measured. After measurements, the same empirical law of grain growth was found for the different alloys and the ln [D-Do] x 1/T diagrams were plotted in order to establish the kinetic behavior. Based on the estimated values of the activation energy, important conclusions were obtained concerning the addition elements. Keywords: microstructural evolution of the CuZnAl, effect of B and Fe on the CuZnAl alloys, kinetics and morphology of CuZnAl. alloys IntrodutionThe alloys of the CuZnAl system with shape memory effect present two problems that hinder their employment on an industrial scale: these are the natural ageing and the grain growth observed during thermomechanical processing. The first degrades the shape memory effect, while the second, observed during thermomechanical processing of the alloy, displaces the temperatures where the thermoelastic transformations are observed. The extent of the ageing and grain growth can be reduced by control of the rate of atomic diffusion of the solute elements from the matrix to the grain boundaries. This control can be obtained indirectly by increase of the activation energy of diffusion, which can be produced through the addition of microelements in the alloy.After academic euphoria concerning the phenomenological aspects of the shape memory effect, researche on the physical metallurgy turned over to the microstructural control of the alloy, in an attempt to eliminating such typical problems as ageing and grain growth. The traditional method for the stabilization of the microstructures was the addition of alloy microelements. For shape memory copper-based alloys, several microelements have been used. Wang. et al.1 verified the influence of zirconium, titanium, boron and iron on the refinement and the stabilization of grains in an alloy of the CuZnAl system. Morris et al. 2,3 verified the influence of simultaneous use of manganese and boron on the thermoelastic effects and the mechanical properties of a CuAlNi system.For any copper alloy system, the problem is the same: determining the amount required of the microelements to be added to the alloy system, while maintaining the ability for plastic forming required for the manufacturing process. In this work, therefore, the effects of the addition of B, Fe ...
The purpose of this study is to evaluate the effect of the stages and tempering temperatures in the microstructure, tenacity and hardness of the vacuum sintered high speed steel AISI T15. The material was uniaxial pressing at 700 MPa and sintered in a vacuum furnace at 1275°C. After that, different samples of the materials were submitted to the annealing treatment at 870°C, quenching at 1235°C and tempering (single, double and triple) at 540, 550 and 560°C. Concluded the treatments, Rockwell C measurements of hardness were accomplished and, to evaluate the toughness of the material, TRS (Transverse Rupture Strength) tests were done. Later on, the materials were submitted to the metallographic preparation for microstructure analysis in optical microscopy, SEM, EDX and X-ray diffraction. Finally, each property analyzed was evaluated and correlated with the different tempering stages and temperatures accomplished.
The use of pressed and sintered aluminum, obtained by the powder metallurgy route, to produce large quantities of near-net-shaped components is increasing rapidly in the automobile industry. The production of lightweight pieces of Al by powder metallurgy has attracted increasing attention due to its unique properties. Sintering helps develop mechanical strength and other properties in commercial alloys obtained by powder metallurgy. Sintering of Al can be achieved only upon formation of a liquid phase capable of destroying the extremely stable oxide layer on the surface of the Al particles. The aim of this investigation was to analyze the effect of compaction pressure on sintering of atomized ASTM 2124 type alloy. Powder characterization was carried out using scanning electron microscopy (SEM). The specimens were axially compacted at pressures of 500, 600 and 700 MPa. Differential scanning calorimetry (DSC) was carried out to determine the sintering temperature of the alloy powder. The specimens were sintered at 570° C. Characterization of the sintered material consisted of density measurements and optical as well as SEM examinations. Nevertheless, even the low recycling cost of Al , what increases its useful time and stabilizes its value, the large amount of energy required to obtain it reduce its application.
This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composite Beams (SMAHC), that consist of a circular bar of NiTi alloy incorporated in a 500 mm long cylindrical pipe of polypropylene (PP), with external diameter 50 mm and nominal wall thickness 7 mm, wound with a nylon/epoxy layer. The Ni-Ti alloy was characterized using: scanning electron microscopy (SEM); X-ray diffraction (XRD) and Differential thermal analysis (DSC). The nominal chemical composition of the alloy is 50.05 %Ni / 49.95%Ti, and the softer martensite is the predominant phase at room temperature. The approximate martensite (M) to Austenitic (A) phase transformation temperatures were Mstart = 32°C, Mfinal = 46°C, Astart = 38 °C and Afinal = 60°C. For temperature T<Mfinal, Ni-Ti bar presents 100% martensitic phase, whereas for T>Afinal it is fully converted in the Austenitic phase; and its elasticity modulus increases by a factor up to three times. This significant change in stiffness of Ni-Ti, without changing its mass, has motivated the application of such alloy in machine vibration control. The SMAHC beams were subjected to static three-point bending tests, in the elastic regime. Experimental results showed that, in average, at 21°C, the PP pipes effective flexural elastic modulus increased 112%, from 757 MPa to 1609 MPa, when the Ni-Ti bar and the external layer of nylon/epoxy were incorporated to the PP pipe, creating a smart beam. These last results indicate that the SMAHC beam can work as an adaptative structure.
This work aims to investigate the influence of tempering temperature in the wear resistance of AISI T15 HSS tools produced by two different sintering processeshot isostatic pressing (HIP) and liquid phase vacuum sintering. All materials are submitted to annealing at 870ºC, quenching at 1210ºC and triple tempering at 540, 550 and 560 ºC. Density measurements, hardness and bend strength (transversal rupture strength -TRS) tests are accomplished. To identify the present phases and to evaluate the obtained microstructures, analysis in optical microscopy, SEM and EDX are done. Interchangeable inserts are manufactured by electrical discharge machining process. Frontal machining without coolant of normalized AISI 1045 steel plates is employed. The cutting forces are monitored via a transducer basically constituted of an instrumented table with four load cells mounted with "Strain Gages" sensors capable to measure the cutting efforts. The tools wear is analyzed and used to estimate the performance of two different HSS tools. For both investigated materials, the tools tempered at 540 ºC show the lowest wearing. Elements Process
This paper aims to verify the Cu 9 Al 4 phase influence on the nanomechanical behavior of the Cu-14Al-4Ni-xTi alloy obtained by rapid solidification with addition of different amounts of Ti. Using the Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersion Spectroscopy (EDS) and X-Ray Diffraction (XRD), it was possible to perform the samples' microstructural characterization. In addition, the reduction of the Cu 9 Al 4 phase precipitation and the X-phase appearance were verified according to the increase of the titanium percentage added. The nanomechanical behavior was evaluated by nanoindentation tests, which showed a significant decrease of the elastic modules and an increase of the Poisson coefficient's according to the titanium amount. This research establishes that the reduction of Cu 9 Al 4 phase implies on the increase of the capacity to dissipate energy. Therefore, the high damping capacity combined with the X-phase presence increases the super elasticity and the alloy ductility.
The constant search for the improvement of the performance of materials of industrial application, evaluated under aspects of weight reduction, greater resistance, greater resistance to wear and better thermal stability, among others, associated with the search for the development of ecologically viable products, that convert the context of environmental degradation in preservation and sustainability, reflects the need to conduct research that results in new materials. The objective of this work is to obtain composites of the AA6061 aluminum alloy reinforced with different contents of coke coal blast-furnace slag by powder metallurgy. The processing of these materials was done by sieving, mixing and compacting powders of reinforced aluminum alloy with 5, 10 and 15% of blast-furnace slag. The cold uniaxial compaction was realized at a pressure of 500MPa. The obtained materials were sintered at 580°C for 3h under inert atmosphere. Unreinforced aluminum alloy samples were also produced. The characterization of the materials was realized by density and hardness measurements and three-point bending tests. The analysis of its microstructure was realized by scanning electron microscopy. As results, the composites presented a homogeneous distribution of the reinforcing particles and also a progressive improvement of the hardness and the bending strength with the increase of the slag content, producing an increase of 79% in hardness and 128% in flexural strength, when compared to the material without reinforcement obtained by the same process. Such results give the coke coal blast-furnace slag a new possibility of exploitation in the metal-mechanical sector, besides contributing with the environmental issue.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.