This literature survey deals with the prior existing studies which explicate SMAs as common studies, at most the Cu-based SMAs studies since those SMAs are very contrastive from old-style materials. Thus , a deeper thoughtful of their thermo- mechanical behavior and the effect of preparing method , heat treatment, alloying element and other factors on their mechanical and physical properties which is necessary for engineering sciences.
General Literature Review of Shape Memory Alloys :
R.A. Sanguinetti Ferreira et al. (2000)[42] Studied the Microstructural Evolution in a CuZnAl Shape Memory Alloy by indirect techniques relating to the atomic migration rate of grain boundaries. He compared between the master alloy{Cu-15.5wt.% Zn-8wt.%Al} with addition of alloying elements and alloys without any addition ,alloying elements wich added (IRON. BORON ,Titanum). bulk sample was produce by melting technique and casting followed by annealing , all annealed samples were examined by statistical metallography and the grain sizes were measured. From the measurement of In this work, the results showed that the CuZnAl system is extremely sensitive to the variations in the microelement content and the temperature at which the alloy is heat treated, Boron and iron were shown to be effective in refining and stabilizing the microstructure in the Cu-15,5Zn-8,0Al alloy. The increase of the activation energy produced for each element allowed the comparison of its effectiveness in relation to the alloy without any microelement addition.
Mohammed Es. S. et al. (2000) [43] Investigated the mechanical properties, transformation behavior and cytotoxicity of ternary NiTi42Cu7 and binary NiTi42 alloys have been present. The deferential scanning calorimeter found the transformation temperature; by the bending test at a range of temperature (6-603c) the mechanical properties have been investigated. The effects of surface finish and surface topography residues on the potentiodynamic biocompatibility and corrosion behavior were reported. The cytotoxicity investigations included MTT tests it’s also performed for both alloys. The extent of corrosion resistance is also reduced as the surface roughness and the amounts of residues increase. This is thought to be due to surface effects on corrosion and metallic ions release. The transformation behavior of the alloys studied is quite different as a result of different chemical compositions and thermomechanical histories. The existence of copper in the ternary alloy is predictable to decrease the hysteresis of the martensite – austenite transformation temperatures. The ternary alloy displays superior mechanical properties. The superelastic hysteresis stress is lower causing in higher unloading plateau stresses, and the resistance to softening during loading – unloading cycles is better.
S. Kustov. et al. [2002][44] Investigated the inspiration of martensite stabilization at the minimum temperature for non-linear anelasticity in Cu-Zn-Al shape memory alloys, the advanced acoustic technique has been used to investigate the mobility of partial dislocations/intervariant boundaries in the β1′ martensite of a Cu-Zn-Al alloy subjected to the stabilization of martensite and to the β phase ageing, suppressing the stabilization effect. The non-linear anelasticity has been studied for frequencies of about 100 kHz and strain amplitudes 2×10−7–2×10−4 over the temperature range 300–8 K. Measurements at low temperatures, below approximately 70 K, allowed us to eliminate anelastic effects associated with the motion of quenched-in defects, which are ‘frozen’ for these temperatures, and to assess the intrinsic mobility of partial dislocation/intervariant boundaries. The results obtained for stabilized samples are compared with those for β-phase aged samples, and with the previously reported data for the Cu-Al-Ni alloy, which is not prone to the stabilization at ambient temperatures. By suggest distinguishing mechanisms of stabilization according to their localization: a homogeneous and a heterogeneous component. Namely, short-range reordering occurring in the bulk of the crystal is responsible for the homogeneous component of the stabilization. The local rearrangement of the martensite structure in the vicinity of lattice defects (pinning of partial dislocations/intervariant boundaries by quenched-in defects and more intense than in the bulk localized re-ordering) is assumed to be responsible for the heterogeneous component of the stabilization process. The acoustic technique is shown to be able to distinguish and to study details of various effects associated with the heterogeneous and homogeneous changes in the structure of martensite, induced by the stabilization and different heat treatments.
I. Hopulele. et al. (2004)[45] were studied and compared Cu-Zn-Al-type alloy relating to their super elastic behavior and shape memory alloy by set Three alloys which have been studied with the composition ranging between (22.0-22.5)% wt. Zn, (5-6.5) % wt. Al ,balance Cu , attained by melting in an induction furnace and gravitational casting. The samples which were cast from the three alloys have been exposed to loading – unloading trials by stressing by “dilatometric analysis” The shape memory effect (SME) and two way shape memory effects (TWSME) have been studied and the effect of small variations in the Zn and Al compositions on the critical points has been discovered in this study. From the studied Cu-Zn-Al alloys, a small quantity of modification for the chemical composition does not result in important alteration of the unit tensile loading, but it leads to important differences with respect to the shape memory effect and pseudoelastic properties. It is essential to know that the chemical composition has a significant effect on the position of the shape memory effect and the critical temperatures. Taking into account the normal accepted variations of the industrial alloy chemical composition, in the case of the shape memory alloys with prescribed features, it is necessary to intricate a series of alloys with close compositions and to create a selection based on dilatometric analysis.
A. Aydogdu et al. (2004) [46] studied the Long-term ageing behaviour in shape memory Cu–Al–Ni alloys for martensite by evaluated the changes of structure in microscopic scale Metastable beta phases of copper-based ternary alloys are very delicate to transform martensitically from the ordered structures to the long-period layered structures on cooling and the heat treatments. Martensitic transformations in these alloys occur by two or more lattice. Martensitic transformations in these alloys happen by two or more lattice invariant shears on a (0 0 1) plane matrix for austenite, which is stacking plane or basal plane for martensite. The basal plane of 9R (or 18R) type martensites creates from one of the (1 1 0) planes of the parent phase, and a homogenous shear happens on the basal plane in either of two opposite directions during the transformation. The (0 0 1) type plane for parent phase is exposed to the hexagonal distortion with martensite formation on which atom sizes have central effect. when the atoms occupying the lattice sites have the same size, the hexagon converts regular hexagon; else the hexagon undergoes a alteration in case sizes of atom are different. In case sizes of atom are equal, the interplane spacing turn into equal for each other of the particularly selected pairs of diffraction planes providing a special relation between miller indices, although they become different in the case of different atom sizes. By reason of this property, the degree of order in martensite can be obtained from the differences in spacing between the selected pairs of diffraction planes. The change in this difference can be ascribed to the interatomic changes with ageing in the material, and the reduction in spacing difference pointers to disordering in martensite. In the present influence, long-term ageing behavior of the martensite in two shape memory Cu–Al–Ni alloys has been planned by electron microscopy and X-ray measurements.
J. M. Guillemany et al. (2004) [47] “was studied the best grain refiners for copper-based shape memory alloys among three of the most important elements, and then evaluate the kinetic grain growth, and to observe the changes produced in the transformation temperatures and enthalpies with the grain size for each alloy, in various fine-grained Cu-Zn-Al shape memory alloys. Image analysis and calorimetry techniques were used. The study shows that grain boundaries favor martensitic transformation and, at the same time, obstruct retransformation.”
Bangyi Chen et al. (2005)[48] studied the corrosion behavior for copper and the Cu–Zn–Al shape memory alloy (SMA) in” simulated uterine fluid” which included tests of Chemical immersion, atomic absorption spectrometry and electrochemical methods. pH number was very essential which influence on corrosion rate and potential of corrosion is. “The results designated that in the static state in simulated uterine fluid, dealuminumification of the Cu–Zn–Al alloy occurred with Cl− joining with aluminum ions to produce hydroxyl aluminum chloride. The hydroxyl aluminum chloride hydrolyzed readily and eased further corrosion of dealuminumification. The corrosion process of Cu and Cu–Zn–Al SMA in simulated uterine fluid was controlled by cathodic oxygen reduction. Because the affinity for surface ionization is superior for aluminum than for zinc, a compact protective aluminum layer was shaped, which withdrawn the oxygen cathodic reduction. Therefore, the corrosion rate of Cu–Zn–Al SMA was smaller than that of Cu in “simulated uterine fluid”. With increasing pH, the corrosion rate of Cu and Cu–Zn–Al SMA in simulated uterine fluid decreased and the open-circuit potential shifted in a positive direction.
J. V. Wood et al. (2006) [49] was study, the investigation to produce of CuZnAl shape memory alloys by technique of powder metallurgy from pure elemental powders. It has been establish that conventional powder metallurgical path via cold compaction and sintering is not appropriate to the mixtures of elemental Cu, Zn and Al powders because of the vaporization loss of zinc. Though, a hot pressing is a novel technique in such mixtures, has been established to be an effective method avoiding zinc loss. In addition, by hot rolling followed by this novel technique, homogeneous (Cu Zn Al) alloys that display shape memory behavior could be formed from elemental powders.
P. K. Kumar et al. (2008) [50] they studied the shape memoy alloys in general view and investigated the different way to preparation these smart materials also compared the physical and mechanical properties between different types of shape memory alloys and found the properties different from one to another and depended on composition of alloy
P. Heresi et al. (2009)[51] was study dissipate energy through hysteresis cycles without significant residual deformation in shape memory alloy . Two Cu Zn Al alloys were prepared with nominal composition Cu – 16.90%wt.Zn – 7.71%wt.Al – 0.04%wt.B. Alloy A and alloy B were analyzed using optical spectroscopy . A thermo-mechanical treatment was applied to all the plates. It consisted in heating the plate to 850ºC, pressing it to reduce its thickness and finally water quenching ,the plate many tests have been done such as Differential Scanning Calorimeter (DSC) analysis and optical metallographies were performed to samples of the plates to find the phase transformation temperatures Ms , Mf , As and Af , and to verify the initial phase also to measure average grain sizes. He found that both alloy are in martensite phase at room temperature .
L.G. Bujoreanu et al . (2010) [52] was study Degradation of Thermal Memory in a Cu-Zn-Al Shape Memory Alloy throughout thermal cycling with cooling by air, a SMA with chemical composition Cu-15Zn-6Al (mass%) was cast then hot pressed, and hot rolled, after that quenched followed by (a fragment of 57.3 mg was cut and, after careful mechanical removal of any marks of shallow corrosion below water cooling at 1020 K). and then exposed to thermal series with altered temperature cycles he found thatThe maximum and the minimum for the heat flow rate resemble to the shade points of the DSC charts which provide the average transformation rates in the first and the second halves of every opposite transformation process, respectively, After thermal cycling he observed the general shape of martensite was not does no longer happen as plates but slightly as needles, which are thinner and shorter , being distinguishing to lath-martensite. “He considered that heating temperature exceeded 450 K, one could include the potential occurrence of diffusion processes as another probable cause of thermal memory degradation. These processes could easily lead to the brief formation of α1 bainite or to the precipitation of equilibrium α -phase. The previous has diffusion precise growth, and, consequently, hinders transformation reversibility while the second requires the removal of Zn and Al atoms, from the regions occupied by Cu-rich α -phase crystallites to the matrix, therefore increasing Zn and Al concentration and reducing to much transformation temperatures of the matrix. However, one should have in mind that transitory bainite formed only after long isothermal aging, before transforming to equilibrium α-phase, by another mean he noted that the process was moved to lower temperatures and becomes fewer intense, up to total extinction and the gradual loss of thermal memory was attributed to the formation of lath-martensite below the form of stabilized needles interlocking .
Abdul Raheem. K. A. et al (2010)[53] was study the influence of addition of iron on the corrosion behavior and dry sliding wear of Cu Al Ni shape memory alloy by equipped master alloy Cu + 13wt.% Al + 3.8 wt. % Ni by using powder metallurgy. Dry sliding wear has been planned built on pin on disk at constant sliding distance and constant velocity. Corrosion behavior in 5 wt% NaOH media based up on potentiostatic ( Tafel ) which has been obtainable for base shape memory alloy ( Cu + 13% Al + 3.8 % Ni ) in two suitcases austenitic and martensitic phase state,the effect of Fe additions as ( 0.4 , 0.8 and 1.2 wt% ) has been considered in both corrosion resistance and wear resistance, by the result we observed that The specimen in the martensitic structure has more wear resistance than that for austenitic structure . The martensite made during quenching in Cu Al Ni has shape memory effect and superelastic thus that it elastically deformation under loading. This behavior gives the sample in martensitic structure more resistance to mass loss due to sliding effect and friction, the additionof Fe ( 0.4 , 0.8 and 1.2 wt% ) it is displayed that rising iron content leads to increase weight loss per unit surface area. This is possibly due to oxidation effect of iron which has more attraction to interact with oxygen than any other constituent of base alloy .Furthermore the oxide of iron is not protected, porous and not adhered with substrate of the alloy surface, These features lead to rise weight loss with rising Fe content. From the results of corrosion test the current density for sample in austenitic structure ( 633.62μA/cm2 ) is much greater than for martensitic structure ( 336.45 μA/cm2).which demonstrate that shape memory alloys have more corrosion resistance than convention alloys due to behavior of hyper elastic for polycrystalline structure. It is possible that structure order is caused by phase transformation and is affected on the corrosion behavior of (Cu Al Ni )shape memory alloys.
Also it is clear that corrosion current density for ( Cu + 13% Al + 3.8 Ni + 0.4 Fe) is 323.43μA/cm^2 which is minor than corrosion current density for 0.8 and 1.2 wt.% the addition of iron which are 338.97 and 347.22μA/cm2 individually. The iron element is more active than Cu, Ni and Al from the electrochemical series, so the rise in iron content in the base Cu Al Ni shape memory alloy from (0.4 to 1.2 wt. % Fe) raises corrosion rate. Due to the action of iron as the anode and behave of Cu as the cathode and when the cathodic surface area is more than that of the anodic, the corrosion rate or ( corrosion current density) rises. In addition, iron oxide is not protect not adhere to the substrate and it has a porous nature so that the rising of Fe content leads to increase of Fe ions which dissolved in solution.
Sajjad Po. et al. ( 2012) [54] studied in their research the microstructure and properties of Cu-based shape memory alloy produced by hot extrusion of mechanically alloyed powders. Powder Metallurgy was widely used to create a Cu-based shape memory alloys which have a maximum of desired properties. It is superior to use P/M for controlled the composition and grain size and produced near net shape alloy products. In this study, the ball miller higher energy was applied to change the elemental powder mixtures for Cu, Al and Ni into pre alloyed powders. The composition and particles size distribution were effected of milling time which was studied, then the pre alloyed powders were compacted by pressing after that, hot extruded to get the final alloy sample. Strain recovery of the bended samples was studied to evaluate the influence of milling on the shape memory properties. When the samples was green density can calculated, extruded and sintered conditions to investigate the changes in the density of the samples, and porosity effect on the shape memory effect. The results presented that milling time has a variable effect on the density for these samples, which can take effect on the shape memory recovery as a result of porosity amount.
Ausonio Tuissi et al.(2012)[55] studied the foam of CuZnAl Shape Memory Alloys and other extremely porous metallic materials with cellular structures are known to have various interesting combinations of mechanical and physical properties. That makes these systems smart for both functional and structural applications. Cellular metals can be shaped by various methods having liquid infiltration of leachable space. In this influence, results on metal foams of Cu based shape memory alloys (SMAs) processed by molten metal infiltration of SiO2 particles are presented. By using this route, highly homogeneous CuZnAl SMA foams with a spherical open-cell morphologies have been manufactured and tested. Morphological, thermo-mechanical and cycling results are reported.
Jassim Mohammed Salman[56] was researched the corrosion behavior of of CuAlZn Shape Memory Alloys in 3.5 NaCl Solution, “ in this study , Cu-based shape memory alloys of Cu-25Zn-4Al alloy as master alloy have been prepared by powder metallurgy technique in different alloying elements experimental procedure used to prepare samples from the elemental powders across the blending of powders in the operation of mixing, compaction and lastly sintering based upon usual steps of powder metallurgy technique. The used in this study to prepare several alloys with average particle size and purity. The addition of alloying elements such as manganese and titanium with (0.5%wt,0.7%wt and 1%wt ) of each element added to the master alloy.
After mixing of powders ,compaction stresses of (450,550,650 and 750 Mpa) have been used to compact the master alloy to choose best compress . disc samples (13mm in diameter) and cylinder samples (10mm in diameter ) have been prepared by using 650 Mpa as best compress . then sintering process in vacuum tube furnace has been achieved by three stages ,the first stage is at (350˚C) for 2hr. ,second stage is at (550˚C ) for 1hr. and third stage is at (900˚C) for 3hr. all samples are solution treatment by heating up to (850˚C) for (1hr.) then rapid quenched in (ice water +salt ) . The results obtained from this study have been presented .it found that at 650Mpa the green density is( 6.84g/cm³) and green porosity is 16.88% because Green density increases with increasing compaction pressure. Three stages occur during compaction process ,the first stage powder particles are rearranged. In the second stage elastic and plastic deformation of the particles have been took place. The third stage of compaction includes fracture of powder particles which have been embrittled through work hardening. ,while apparent density and porosity of sintering master sample are (4.731 g/cm³) and (25.95%) respectively its increases with compact pressure increases as . because that the space between particles fills with small particles. Corrosion results have been shown that corrosion rate decrease with addition Mn% and Ti% addition alloying where the (Cu-25Zn-4Al-1%Mn) alloy has (10.678 mpy) in sintering state while (Cu-25Zn-4Al-1Ti) alloy has (1.732 mpy) in quenching stateTafel Corrosion has been used to investigate corrosion behavior for the master alloy with addition in sintering and quenching state .the corrosion solution has been used in the test was NaCl solution (3.5gmNaCl + 96.5ml distillation water) at room temperature.” measurements of open circuit potential during 50 second of immersion were performed to obtain some information about the evolution of the corrosion process. Rate of corrosion for sample in austenitic structure is much superior than for martensitic structure .This proves that shape memory alloys have more corrosion resistance than convention alloys due to elastic behavior of polycrystalline, corrosion rate for alloys has been decreased with increasing the percent of alloying elements (Mn ,Ti). Among the alloys, quenched alloy (Cu-25Zn-4Al-1%Ti) has less corrosion rate. (Cu-Zn-Al) shape memory alloy forms intermetallic compound of (γCu5Zn8) in sintering state , also it forms (βCu0.61Zn0.39) in quenching state.
Sathish S1, et al. [2014] [57] studied the Shape Memory Effect and Microstructure of Cu- Zn-Ni Shape Memory Alloys, the morphology and microstructure of martensites formed were studied using an optical microscope. The transformation temperatures were found by using a differential scanning calorimeter (DSC) by approving a heating and cooling rate of 10˚C/min. by using X-ray diffractometer to recognize the phases that formed at room temperature polycrystalline samples were analyzed. The strain recovery by SME of the alloys were found by bend test on 1 mm thick specimens by calculating the initial and final bend angles just before heating i.e. in the martensitic phase, and directly after heating, i.e. in the austenitic phase of the alloys The results display that the recrystallization happens in the hot-rolled Cu-Zn-Ni alloy by annealing at 800˚C and alloy is mainly composed of martensite. an opposite martensite transformation temperature higher than 100˚C upon heating has been noticed. The amount and type of martensite designed in these alloys are mainly in need of the amount of zinc and nickel in the alloys. β1 ′ martensitic phase is predominant in the composition range of the alloys that chosen. Two types of martensites are observed in these alloys i.e. β1 martensite and γ1 ′ martensite with high density of twins. The β1 martensite phase is formed when the zinc content is less and γ1 ′martensite is formed when the zinc content is more in the composition range of the studied alloys. The transformation temperatures are very sensitive to the dissimilarity in zinc concentrations of the alloy. As the content of zinc rises, the transformation temperatures reduction, whereas as the nickel content increases, the transformation temperatures increase too. The alloys display good strain recovery that resources good ductility by SME. A strain recovery up to 99% by SME was detected in these alloys. The difference in nickel and zinc in the concentration of alloys does not meaningfully affect the strain recovery by SME but depends on the type and amount of martensite transformed.
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