Papers by Keyword: Microstructure

Paper TitlePage

Authors: Michel Suéry, Luc Salvo, Charles Josserond, Marco Di Michiel
Abstract: The evolution of the microstructure of semi-solid Al-Cu alloys has been characterized during isothermal treatments in the semi-solid state by using in-situ X-ray microtomography experiments carried out at ESRF, Grenoble. This work is therefore a continuation of previous experiments reported at the 8th S2P Conference in Limassol. Quantitative data are presented dealing with changes with holding time of the solid volume fraction, of the solid-liquid interface area and of the mean and Gaussian curvatures of the solid phase. Discussion of the results is carried out on the basis of the mechanisms involved in semi-solid systems.
231
Authors: Thomas Rieger, Klaus Herrmann, Dagmar Carmele, Stephan Meyer, Thomas Lippmann, Andreas Stark, Wolfgang Bleck, Uwe Klemradt
Abstract: The ‘Quenching and Partitioning’ (Q&P) concept aims to increase the strength level of conventional TRIP-assisted advanced high strength steel (AHSS) by replacing ferritic constituents by tempered martensite. The Q&P heat treatment process involves austenitization and interrupted quenching followed by carbon partitioning from martensite to austenite at elevated temperatures. The final microstructure is traditionally investigated at room temperature after metallographic preparation by microscopy and x-ray analysis with laboratory tubes. Besides other disadvantages the established characterization methods are not adequate to observe the development of the microstructure during Q&P treatment. In the present work the microstructural evolution during Q&P processing was monitored by in-situ diffraction experiments using very hard (100 keV) synchrotron x-ray radiation. Debye-Scherrer rings were recorded as a function of time and temperature during the heat treatment in a state-of-the-art dilatometer (type Bähr DIL805AD) at the Engineering Materials Science beamline HARWI-II (HZG outstation at Deutsches Elektronensynchrotron (DESY), Hamburg). The diffraction patterns contain quantitative information on the phases present in the sample (for more details cf. Abstract Carmele et al, this conference). The evolution of the austenite phase fraction during the partitioning treatment at the quench temperature (1-step Q&P) is discussed exemplarily for a Si-based TRIP steel with additions of Ni.
713
Authors: Artur Medvid', Pavels Onufrijevs, Edvins Dauksta, Volodymyr Kyslyi
Abstract: The possibility to form “black silicon” on the surface of Si structure by Nd:YAG laser radiation has been shown. The shape and height of micro-cone structure strongly depends on Nd:YAG laser intensity and number of laser pulses. Light is repeatedly reflected between the cones in the way that most of it is absorbed. Si micro-cone structure spectral thermal radiation is close to black body spectral radiance, which makes this structure useful for solar cells application. The micro-chemical analysis performed by SEM has shown that the microstructures contain NiSi2. This was approved by presence of LO phonon line in Raman back scattering spectrum. The control of micro-cone shape and height was achieved by changing the laser intensity and number of pulses.
44
Authors: Philippe Viot, Ali Chirazi, Michel Dumon, Dominique Bernard, V. Fascio
Abstract: Syntactic foams are widely used in many impact-absorbing applications and can be employed as sandwich core. To improve their mechanical performances, these composite sandwich structures have to be modelled. This approach requires the characterisation of the foam behaviour. Moreover, the microstructure of the syntactic foam has an influence on its macroscopic behaviour; the foam density, the diameter of the porosities, their distribution in the material have to be taken into account.
42
Authors: Sundaram Kumar, Sam Agarwal, Keyna O'Reilly
Abstract: Master alloys are used in the metals industry to control chemical composition and to help to achieve a particular microstructure or promote growth of desired phases. This study reports on making a Al3Nb containing aluminium (Al) - niobium (Nb) master alloy by solid-liquid reaction processing, where solid Nb particles are added to the liquid Al. Nb react with Al to form in-situ Al3Nb. The in-situ formed Al3Nb particles were facet and polygonal in shape. The three dimensional analysis revealed that the outer surface of the partially reacted Nb was covered with faceted Al3Nb particles. The different nature and morphologies of the in-situ phases that were produced were determined using SEM, EDX, XRD and extraction techniques. A mechanism for the observed microstructural difference is discussed.
515
Authors: Sundaram Kumar, Sam Agarwal, Keyna O'Reilly
Abstract: Master alloys are used in the metals industry to control chemical composition and to help to achieve a particular microstructure or promote growth of desired phases. This study reports on making a Al3Nb containing aluminium (Al) - niobium (Nb) master alloy by solid-liquid reaction processing, where solid Nb particles are added to the liquid Al. Nb react with Al to form in-situ Al3Nb. The in-situ formed Al3Nb particles were facet and polygonal in shape. The three dimensional analysis revealed that the outer surface of the partially reacted Nb was covered with faceted Al3Nb particles. The different nature and morphologies of the in-situ phases that were produced were determined using SEM, EDX, XRD and extraction techniques. A mechanism for the observed microstructural difference is discussed.
131
Authors: Gui Rong Li, Yu Tao Zhao, Hong Ming Wang, Gang Chen
Abstract: (Al3Ti)p/6351 composites were in situ synthesized via direct melt reaction between 6351 wrought aluminum alloy and K2TiF6 at 720°C. OM, SEM and EDS are utilized to analyze the microstructure and components of composites. The fusing agents of CaF2 and LiCl are mixed with K2TiF6 to lower the temperature of initial in situ reaction. The volume fraction of Al3Ti is 3%.The size of Al3Ti is in the range of 2~4μm, which is much lowered than that fabricated by conventional process. Due to the calcium element from CaF2 the size of Mg2Si phases are decreased to 1~2μm.The microns of independent silicon phases are also observed in the squeezed section. The grain size of α-Al is fined to 30~40μm, which is due to the disperse effect of Al3Ti. The tensile, yield properties and elongation are at room temperature are 365MPa, 320MPa and 10.2%.
1437
Authors: Ying Gao, Dei Gui Zhu, Ling Cheng, Hong Liang Sun, Qing Wang
Abstract: Particles reinforced Al-xwt.%Si-Al2O3 (x=10,20) composites are fabricated through in situ reaction sintering of Al and SiO2 powder by hot isostatic pressing. Outgassing process and the microstructure of composites under different sintering processes are studied.XRD analysis confirms that the best hot outgassing temperature is 500°C,in situ reaction achieves completely and samples A2 and B2 have better microstructure at 550°C then heating-up to 700°C only for 1h.The microstructure analysis indicates that the reinforcement particulates distribute uniformly in the aluminum matrix.The mechanical properties test results show that the tensile strength of A2 is higher than B2. when x=10,the Al-Si-Al2O3 composites have better performance.
38
Authors: Yao Ning Sun, Ding Fan, Yu Feng Zheng, Min Zheng, Jian Bin Zhang
Abstract: Laser cladding technique was used to form Ni3Si intermetallic composite coating reinforced by in-situ formation NbC particles on Ni-based superalloy substrate. The process parameters were optimized to obtain cladding. The effect of Nb-C addition to the microstructure of the coating was investigated. The morphology of reinforcement particles was discussed. The experimental results showed that an excellent bonding between the coating and the substrate was ensured by a strong metallurgical interface. The clad coating was very good and free from cracks and pores. The microstructure of the coating was mainly composed of Ni(Si), Ni3(Si, Nb) and NbC. The NbC particles were formed by in-situ reaction between Nb and C during laser cladding process. NbC particles were homogeneously distributed in the composite material. Moreover, the maximum size of NbC particles was more than 4 μm.
1351
Authors: Hai He Luo, Qi Zhou Cai
Abstract: A ZrO2-Y2O3-containing composite ceramic coating was firstly in situ prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in an alkaline silicate-containing electrolyte. The morphology, chemical composition and corrosion resistance of the PEO coating were investigated by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectrometer, dropping corrosion and electrochemical corrosion test. The results showed that the ceramic coating consisted of two distinct structural layers: an outer loose layer and an inner dense layer; it was composed of t-ZrO2, Y2O3, SiO2 and some magnesium compounds, such as MgO, MgF2 and Mg2SiO4. In addition, the ceramic coating also showed excellent dropping and electrochemical corrosion resistance, which was mainly attributed to its special phase composition and microstructure.
1684
Showing 1 to 10 of 7204 Paper Titles