Papers by Keyword: Nanoindentation

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Authors: Y.L. Chiu, V. So, Zheng Wei Li
Abstract: In this work, we report our study of the microstructure and mechanical properties of pure Ti, Ti-11Al, Ti-47Al and Ti-6Al-4V nanostructure coatings on AZ91D Mg alloys prepared using DC magnetron sputtering. The fine structures of the coating (see fig. 1 for Ti-6Al-4V coating) are presented. The hardness of the coatings were tested on a CSEM nano-hardness tester with a Berkovich diamond intender. Hardness values were obtained from analyses using the Oliver-Pharr scheme. The hardness of the nanostructure coating increases from about 3.5GPa up to about 6.8GPa when the aluminium concentration increases from zero to 47at.%. Maximum hardness value was found on the Ti-6Al-4V coating, about 7.3GPa. The elastic modulus of the pure Ti coating has the lowest modulus and strain burst “pop-in” has been observed on Ti-47Al coating.
Authors: Agnieszka Twardowska, Bogusław Rajchel, Lucyna Jaworska
Abstract: Ti–Si–C coatings were formed at room temperature on AISI 316L steel substrates by dual beam ion assisted deposition technique from single compound Ti3SiC2 target. Scanning and transmission electron microcopy method were used to examine as-deposited coatings. Their morphology was smooth and dense and their thickness were in the range from 100 nm to 1μm. Raman spectra of coated substrates were collected up with five peaks at the same positions as for Ti3SiC2 compound target. TEM and HRTEM examinations, accompanied by SAED analyses revealed that deposited films were amorphous. Nanoindentation tests were provided on coated and uncoated substrates and hardness HIT and reduced elastic modulus EIT were calculated using the Oliver & Pharr method.
Authors: Ming Zhou, X.D. Liu, S.N. Huang
Abstract: The development of the capability to machine glass materials to optical quality is highly desirable. In this work, the deformation characteristics of brittle materials were analyzed by micro and nano indentations. Diamond cutting of optical glass BK7 was performed in order to investigate the tool wear mechanism in machining of brittle materials and the effect of tool vibration on material removal mechanism. The tool wear mechanism was discussed on the basis of the observation of wear zone. Ductile-mode cutting has easily been achieved with the application of ultrasonic vibration during cutting of glass. It was confirmed experimentally that the tool wear and surface finish were improved significantly by applying ultrasonic vibration to the cutting tool.
Authors: J. Xu, Jérôme Favergeon, P.E. Mazeran, Gérard Moulin, C. Vu
Abstract: This contribution presents results which show the possibility to develop protective coatings from perhydropolysilazane (PHPS) on low carbon steel. In order to have an effective protection, the pyrolysis conditions should be carefully controlled. Nanoindentation tests allow characterizing the mechanical resistance of the coating after different pyrolysis conditions. The pyrolysis of coated samples has also been monitored by acoustic emission; the results show that the structural conversion of the coating from polymer to ceramics can be detected by acoustic emission.
Authors: Sergio Graça, Rogerio Colaço, Rui Vilar
Abstract: When atomic force microscopy is used to retrieve nanomechanical surface properties of materials, unsuspected measurement and instrumentation errors may occur. In this work, some error sources are investigated and operating and correction procedures are proposed in order to maximize the accuracy of the measurements. Experiments were performed on sapphire, Ni, Co and Ni-30%Co samples. A triangular pyramidal diamond tip was used to perform indentation and scratch tests, as well as for surface visualization. It was found that nonlinearities of the z-piezo scanner, in particular the creep of the z-piezo, and errors in the determination of the real dimensions of tested areas, are critical parameters to be considered. However, it was observed that there is a critical load application rate, above which the influence of the creep of the z-piezo can be neglected. Also, it was observed that deconvolution of the tip geometry from the image of the tested area is essential to obtain accurate values of the dimensions of indentations and scratches. The application of these procedures enables minimizing the errors in nanomechanical property measurements using atomic force microscopy techniques.
Authors: Rwei Ching Chang, Feng Yuan Chen, Chang En Sun
Abstract: This work uses nanoindentation and nanoscratch to measure the mechanical properties of evaporation copper thin films. The thin film is deposited on a silicon wafer substrate by using the physical vapor deposition method provided by a resistive heating evaporator. The mechanical properties are then determined by indentation test and lateral force test produced by nanoindenter and nanoscratch. The results show that, as the copper thin film is 500nm in thickness and the indentation depth increases from 100nm to 400nm, the Young’s modulus increases from 151GPa to 160GPa while the hardness increases from 2.8GPa to 3.5GPa. Moreover, both the Young’s modulus and the hardness decrease as the thickness of the thin film increases. Besides, the nanoscratch results show that the friction factor also increases as the scratch depth increases, and a thinner film thickness makes a larger friction factor. The results represent the substrate has a significant effect on the mechanical properties of the thin films.
Authors: Jiří Buršík, Ivo Kuběna, Vilma Buršíková, Pavel Souček, Lukáš Zábranský, Saeed Mirzaei, Petr Vašina
Abstract: Several W-B-C layers were prepared by magnetron sputtering. The microstructure of thin layers was observed by means of scanning and transmission electron microscopy on cross sections prepared using a focused ion beam. Both undisturbed layers and the volume under indentation prints were inspected. The W-B-C layers are fine nanostructured materials about 2 μm thick and indents with loads up to 1 N do not cause any visible defects (cracks, delamination etc). The results were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime using a Berkovich indenter. Elastic modulus, indentation hardness and fracture resistance of prepared nanostructured coatings were evaluated and discussed.
Authors: Yun Hee Lee, Yong Hak Huh, Ju Young Kim, Seung Hoon Nahm, Jae Il Jang, Dong Il Kwon
Abstract: We tried to apply the nanoindentation technique to yield strength characterization by modifying a previous research. Although the yield strength determining technique developed by Kramer et al. has been successfully demonstrated for large scale indentations on bulky metals, its applicability is still doubtful to nanoscale indentations on thin films with severe roughness, anisotropy, and interfacial constraint. In order to overcome these problems, we combined the nanoindentation technique with a three-dimensional indent visualization technique in this study. Nanoindentation tests were performed for Au and TiN thin films and their corresponding indents were scanned by using an atomic force microscope. From the three-dimensional pile-up morphology, a circular pile-up boundary was measured and input into the yield strength formulation as an effective yielded zone radius. The yield strengths calculated were directly compared with those from the microtensile test.
Authors: S.K. Balijepalli, Riccardo Donnini, S. Kaciulis, Roberto Montanari, A. Varone
Abstract: AISI 316L steel, subjected to a low temperature carburizing treatment (kolstering), has been examined by Mechanical Spectroscopy (MS) and nanoindentation to determine the Youngs modulus of the surface hardened layer (S phase). MS results showed that the average value of elastic modulus of S phase is 202 GPa, a little higher than that of the untreated material.Nanoindentation tests, carried out with loads of 5, 15 and 30 mN, evidence a modulus profile vs depth: E is ~ 400 GPa at a distance from the surface of ~ 110 nm, then decreases to reach the value of the steel substrate (190 GPa) at 33 μm.These results, together with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements of carbon concentration profile, can be explained by considering the presence of a very thin surface layer, different from S phase and consisting of a mixed structure of Diamond-like carbon (DLC) and tetrahedral carbon (taC).Furthermore, the same experiments have been carried out also after heat treatments at 450 °C to correlate the modulus change to the decomposition of the metastable S phase leading to the formation of (Cr,Mo)C and Cr23C6 carbides in a Cr-depleted austenitic matrix.
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