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Copyright of Journal of Mining & Metallurgy. Section B: Metallurgy is the property of Journal of Mining & Metallurgy and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Kemija u Industriji is the property of Croatian Society of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The aim in this work was to investigate the change in microstructure, phase transformation temperatures, and thermal properties due to the quenching of the investigated Cu-Al-Mn and Cu-Al-Mn-Ti alloys in ribbon form. This paper presents the results of microstructure analysis and thermal properties of Cu-Al-Mn and Cu-Al-Mn-Ti shape memory alloys produced in ribbon form by melt spinning technique. The microstructural analysis was carried out before and after quenching. After casting of the investigated alloys, annealing at 900 °C for 30 min was performed, followed by water quenching. The microstructural analysis was carried out by optical and scanning electron microscopy equipped with an energy dispersive spectrometer and by X-ray diffractometer. Thermodynamic calculation of a ternary Cu-Al-Mn system in equilibrium condition was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry and electrical resistance measuring. The results of microstructural analysis show the presence of martensite microstructures before and after quenching in the Cu-Al-Mn alloy, while in the Cu-Al-Mn-Ti alloy martensite microstructure exists only after quenching. Phase transformation temperatures decreased after quenching and titanium addition. [ABSTRACT FROM AUTHOR]

This paper presents the results of thermal and microstructural analysis of Cu-Al-Ni shape memory alloy before and after heat treatment. After casting, a bar of Cu-12.8 Al-4.1 Ni (wt.%) alloy, obtained by the vertical continuous casting technique, was subjected to a certain heat treatment procedure. Solution annealing was performed at 850 °C for 60 min, followed by water quenching. Tempering was then performed at four different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The microstructural results were obtained by optical and scanning electron microscopy. Thermodynamic calculation of ternary Cu-Al-Ni system under equilibrium was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry (DSC). The DSC results show the highest values of transformation temperatures in as-cast state. After solution annealing and tempering, the transformation temperatures show lower values with exceptional stability of Ms temperature (martensite start temperature). [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) have been extensively investigated because of their unique shape memory behaviour, i.e. their ability to recover their original shape they had before deformation. Shape memory effect is related to the thermoelastic martensitic transformation. Austenite to martensite phase transformation can be obtained by mechanical (loading) and thermal methods (heating and cooling). Depending on thermomechanical conditions, SMAs demonstrate several thermomechanical phenomena, such as pseudoelasticity, superelasticity, shape memory effect (one-way and two-way) and rubber-like behaviour. Numerous alloys show shape memory effect (NiTi-based alloys, Cu-based alloys, Fe-based alloys etc.). Nitinol (NiTi) is the most popular and the most commonly used SMA due to its superior thermomechanical and thermoelectrical properties. NiTi alloys have greater shape memory strain and excellent corrosion resistance compared to Cu -- based alloys. However, they are very costly. On the other hand, copper-based alloys (CuZn and CuAl based alloys) are much less expensive, easier to manufacture and have a wider range of potential transformation temperatures. The characteristic transformation temperatures of martensitic transformation of CuAlNi alloys can lie between -200 and 200 °C, and these temperatures depend on Al and Ni content. Among the Cu -- based SMAs, the most frequently applied are CuZnAl and CuAlNi alloys. Although CuZnAl alloys with better mechanical properties are the most popular among the Cu-based SMAs, they lack sufficient thermal stability, while CuAlNi shape memory alloys, in spite of their better thermal stability, have found only limited applications due to insufficient formability owing to the brittle γ2 precipitates. The most important disadvantage of polycrystalline CuAlNi alloys is a small reversible deformation (one-way shape memory effect: up to 4 %; two-way shape memory effect: only approximately 1.5 %) due to intergranular breakdown at low stress levels. The technologies for production of shape memory alloys are induction melting, vacuum melting, vacuum arc melting, following hot and cold working (forging, rolling, wire drawing). In addition, rapid solidification methods, like melt spinning and continuous casting have been developed. These methods are characterized by high cooling rates. High cooling rates allow very short time for diffusion processes and may lead to extremely fine microstructure, better homogeneity etc. SMAs have found applications in many areas due to their thermomechanical and thermoelectrical properties (biomedical applications, engineering industry, electrical industry). In this paper, a review of shape memory alloys, properties and applications of mentioned materials is presented. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) belong to a group of functional materials with the unique property of "remembering" the shape they had before pseudoplastic deformation. Such an effect is based on crystallographic reversible thermo-elastic martensitic transformation. There are two crystal phases in SMAs: the austenite phase (stable at high temperature) and the martensite phase (stable at low temperature). Austenite to martensite phase transformation can be obtained by mechanical (loading) and thermal methods (heating and cooling). During martensitic transformation, no diffusive process is involved, only inelastic deformation of the crystal structure. When the shape memory alloy passes through the phase transformation, the alloy transforms from high ordered phase (austenite) to low ordered phase (martensite). There are two types of martensite transformations. First is temperature-induced martensite, which is also called self-accommodating (twinned) martensite. The second is stress-induced martensite, also called detwinned martensite. The entire austenite to martensite transformation cycle can be described with four characteristic temperatures: Ms -- martensite start temperature, Mf -- martensite finish temperature, As -- austenite start temperature, and Af -- austenite finish temperature. The main factors influencing transformation temperatures are chemical composition, heat treatment procedure, cooling speed, grain size, and number of transformation cycles. As a result of martensitic transformation in SMAs, several thermomechanical phenomena may occur: pseudoelasticity, shape memory effect (one-way and two-way SME) and rubber-like behavior. Pseudoelasticity occurs when the SMA is subjected to a mechanical loading at a constant temperature above Af. The second thermomechanical behaviour that can be observed in SMA is the shape memory effect (SME), mainly one-way SME, which is the most commonly used SME. When the sample is subjected to a mechanical loading, the stress reaches a critical value and the transformation of twinned martensite into detwinned martensite begins and finishes when the loading process is finished. When the loading-unloading process is finished, the SMA presents a residual strain recoverable by alloy heating, which induces the reverse phase transformation. As a result, the alloy recovers to its original shape. In this paper, a review of thermomechanical properties of shape memory alloys and general characteristics of martensite transformations is shown. [ABSTRACT FROM AUTHOR]

Abstract The influence of processing, heat-treatment and aging of Cu-(8–9) wt% Al-(7–10) wt% Mn alloy on the kinetics and temperatures of martensitic transformation was investigated by calorimetric measurements. Cu-Al-Mn alloy was prepared by continuous casting, melt-spinner and by melting in the electric arc furnace. Alloys were further heat-treated at 900 °C for 30 min and quenched in water, as well as aged at 300 °C for 1 h. Differential Scanning Calorimetry (DSC) was performed at 3 heating/cooling cycles from −50 to 250 °C. Non-isothermal measurements were determined at five different heating/cooling rates: 5, 10, 15, 20 and 25 °C/min. Activation energy was obtained according to Ozawa and Kissinger kinetic models. Microstructure analysis of investigated systems was performed by scanning electron microscopy (SEM). Results indicate the most intensive formation of martensitic structure in the as-cast state during continuous casting, where the partially formation of needle-like and V-shape martensite was observed. After solution treatment and quenching as well as aging, completely martensitic phase occurred in continuously cast alloy. XRD analysis detected Cu 2 AlMn, Cu 3 Al and Al 4 Cu 9 phases in quenched specimens of continuously cast Cu-Al-Mn alloy and ribbon. The highest impact of the solution treatment and aging on the shifting of the martensitic temperatures was observed for Cu-Al-Mn ribbons, while in continuously cast Cu-Al-Mn alloy heat treatment and aging induced formation of different martensitic crystal structures. Kinetic investigations showed increasing start martensitic temperatures, M s , and wider temperature interval of martensitic transformation with higher cooling rate. The highest values of activation energy of martensitic transformation was obtained for the continuously cast Cu-Al-Mn alloy. Highlights • Cu-Al-Mn SMA by continuous casting and melt-spinner was successfully produced. • Heat-treatment of Cu-Al-Mn SMA results in formation of intensive martensite. • γ' martensite is formed by melt-spinner, β' by continuous casting (Cu 3 Al, Cu 2 AlMn). • Heat-treatment increases M s of continuously cast SMA, and decreases in ribbon. • Cu-Al-Mn ribbon has the lowest energy of activation of martensitic transformation. [ABSTRACT FROM AUTHOR]