Papers by Keyword: Shape Memory Behavior

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Authors: Kurnia Hastuti, Esah Hamzah, Jasmi Hashim
Abstract: In this study, a commercial Ti-50.7at.%Ni was subjected to solution treatment at 800oC and 900oC for one hour followed by ageing at 300oC, 400oC, 500oC and 600oC for 1 hour, 2 hours and 4 hours respectively. Characterization of the material using optical microscope, XRD, FESEM and EDX has shown that the presence of Ti2Ni and Ti-rich precipitates in the as-received material remained unchanged even after heat treatment. The presence of oxygen in the air condition heat treatment has stabilized Ti2Ni since this condition causing the formation of Ti4Ni2O which is also determined as Ti2Ni due to their same crystal structure. The formation of Ti3Ni4 precipitates during ageing encouraged the establishment of R phase instead of martensite due to the depletion of Ni content in the matrix. Ageing treatment at 300oC generates two steps of R phase transformation due to the differences in Ni composition in the matrix at the grain boundary and grain interior region. However, for samples subjected to ageing at higher temperature, 400-500oC, only one step of R phase transformation occurred because Ni atomic diffusion was not forbidden in the high temperature. Hardness test performed on the samples revealed that increasing the ageing time will increase the hardness of material; however for the sample aged at 600oC, increasing the ageing time would reduce the hardness due to dissolution of Ti3Ni4 precipitaes into the matrix.
Authors: Tetiana Kosorukova, Georgiy Firstov, Yuri Koval, Volodymyr Ivanchenko, Jan Van Humbeeck
Abstract: Intermetallic compounds of ZrNi-ZrCo cross-section undergo martensitic phase transformation, which is accompanied by the imperfect shape memory effect at elevated temperatures. Martensitic transformation is also taking place in one of the constituents for the in-situ composites of ZrCo-Zr2Co-Zr2Ni-ZrNi region. High temperature shape memory behavior of Zr-Ni-Co composite material shows improvement in shape recovery comparing to quasibinary intermetallic compounds of ZrNi-ZrCo cross-section.
Authors: Hideki Hosoda, Shinsuke Takeuchi, Tomonari Inamura, Kenji Wakashima, Shuichi Miyazaki
Abstract: A new type of smart composite developed in our group was studied in terms of shape memory behavior. The smart composites were composed of NiMnGa ferromagnetic shape memory alloy particles (FSMAP) and a polymer matrix, where NiMnGa FSMAP will bring shape memory effect and the matrix polymer enhances ductility. Two kinds of NiMnGa were selected by taking the phase constitution into account (parent or martensite state at room temperature). The shape memory properties are reported in terms of transformation temperature, powder size, applied stress and heating/cooling rate. It was found that martensitic transformation temperatures of the smart composites obtained by differential scanning calorimetry (DSC) were almost equal to those of NiMnGa FSMAPs. The shape recovery of the composites was confirmed in the strain-temperature curves obtained by dynamic mechanical analysis. Clear shape change was recognized corresponding to the martensitic transformation temperatures. The shape memory properties depend on heating/cooling rate, particle size and applied stress. Lower heating/cooling rate and smaller particle size brings better shape memory properties. This is because thermal conductivity of polymer is low and the amount of defects such as pores introduced during curing decreases with decreasing particle size. The improvement of processing is needed to reduce material defects.
Authors: Georgiy Firstov, Yuri Koval, Jan van Humbeeck, Andrey Timoshevskii, Tetiana Kosorukova, Pavlo Verhovlyuk
Abstract: Nowadays, martensitic transformation and shape memory effect, superelasticity, high damping capacity and other effects associated with this type of structural phase transitions are still in the focus of scientists and engineers, especially once these phenomena are taking place at elevated temperatures. The list of the materials undergoing this kind of transformation is constantly widening. Yet, industrial application of these materials, called high temperature shape memory alloys, is still hindered due to the lack of understanding of the peculiarities of the high temperature martensitic transformation and shape memory effect. Present work summarizes results of scientific studies of these high temperature phenomena oriented onto the development of physical principles suitable for industrial high temperature shape memory alloys design.
Authors: Jin Lian Hu, Zheng E Dong, Yan Liu, Yi Jun Liu
Abstract: Shape memory polymers are a promising class of stimuli-responsive materials that have dual-shape capability. This kind of materials can recover their shape in a predefined way from temporary shape to desired permanent shape when exposed to an appropriate stimulus. In the development and extensive application of synthetic shape memory polymers on textile industrials, the thermal and hygrothermal effects of wool materials have attracted considerable attention. In this article the fundamental concept of the shape memory polymers and the fundamental aspects of the shape-memory effect were reviewed. The thermal and hygrothermal effects of wool materials were also summarized to discuss the shape memory behavior of wool materials. Besides the effects of synthetic shape memory polymers on the thermal and hygrothermal of the woven wool fabrics were introduced to show the shape memory behavior of treated wool further.
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