Papers by Keyword: Secondary Phases

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Authors: Wen Jun Lu, Rong Shan Qin
Abstract: Thermal crack initiation and pitting corrosion are frequently caused by the formation of the secondary phases such as sigma phase, delta-ferrite phase, carbides and secondary austenite phase in steel. Traditionally, heat treatment is used to minimize these detrimental effects of the secondary phases. In this study, we have applied pulse to the 316L stainless steel and observed the considerable effects. In comparison to the heat treatment, the electropulsing can effectively suppress the precipitation of the secondary phases in a temperature range (1161 K–1173 K). Austenite grain size becomes larger under electropulsing compared to the heat treatment at annealing temperatures due to enhanced interface migration. The kinetic and thermodynamic aspects of electropulsing can be used to explain the effects of electropulsing on the evolution of microstructure for 316L stainless steel.
Authors: Martin Sondel, Jaroslav Koukal, David Schwarz, Drahomir Schwarz
Abstract: Development of new steels with higher creep resistance must be based on detailed knowledge of strengthening and degradation processes, structural stability at high temperature exposure and their welding. This paper is concerned with the real weld joint hardness and microstructure of progressive low alloy creep resistance T24 steel. These steel is widely used in many power-plant constructions all over the Europe. Welding the T24 steels components is one of the most important technological procedures. The aim of the performed investigation is to evaluate the hardness and microstructure in the heat affected zone (HAZ) and the weld metal. Results of the secondary hardening in the real weld joints after low temperature post weld heat treatment (460°C/48h) and without post weld heat treatment at service temperature are described in this paper. Obtained results are compared to the hardness values of the weld joint post weld heat treated at recommended temperature (740°C). The microstructure of the real weld joints was analysed by transmission electron microscopy (TEM) in order to identify minority phases - MX nanoparticles and/or coarse (M23C6) particles. Secondary hardening of the not heat treated and low temperature heat treated T24 weld joint was proved.
Authors: Eing Kuan Kok, Johar Banjuraizah, Li Ngee Ho, Zabar Yahidah
Abstract: The Cordierite ceramic body had been synthesized through conventional techniques solid state reaction by using non-stoichiometric composition (2.5 MgO. 1.8 Al2O3. 5 SiO2). The sintering temperature study was carried out by heat treated the samples at several degree of sintering temperature (1250 °C, 1275 °C, 1300 oC, 1325 °C, 1350 °C and 1375 °C). The qualitative and quantitative of crystalline phase analysis was accomplished by using X-ray Diffraction (XRD) technique and Rietveld structural refinement. The Scanning electron microscopy (SEM) was employed for morphology analysis. The mechanical properties of samples were determined by Vicker’s Hardness test. Rietveld quantitative phase analysis results show that α phase Cordierite constitutes up to 96.4 wt% when the samples was sintered for 2 hours at sintering temperature of 1375 °C and obtained densified and orderly crystal structure arrangement in SEM micrograph except the mechanical strength. The sample obtained the uppermost α phase Cordierite content gained the lowest hardness values (4.00.8GPa). Conversely, the sample contains 90 wt% α-cordierite and 1.4 wt% magnesium titatnate achieve highest hardness which is about 4.90.79GPa.
Authors: Jean-Marc Tulliani, L. Dessemond, P. Fabry, Claude Esnouf, Gilbert Fantozzi
Authors: De Bin Shan, X.Z. Han, Wen Chen Xu
Abstract: The isothermal forging process of a bracket and its microstructure evolution of Mg-10Gd-2Y-0.5Zn-0.3Zr alloy have been investigated in the present study. The results show that the bracket with thin-web and high-rib is well formed through modifying corners and adding an active damping block into male die. Amounts of lamellae and particles distribute uniformly on the matrix after the isothermal forging process and ageing process. The isothermal forging process has an obvious effect on the precipitation behaviour of secondary phases, while it did not change the grain size greatly. With the increase of ageing time, more secondary phases precipitate from α-Mg matrix until 60h. The optimal ultimate tensile strength and elongation of the peak-aged alloy are 382MPa and 4.03%, respectively. The combined effects of LPO and β′ phases contribute to the high strength of the peak-aged alloy.
Authors: V. Nadenau, H.-W. Schock, M. Krejci, F.-J. Haug, A.N. Tiwari, H. Zogg
Authors: Shu Guo, Zhi Liang Ning, Fu Yang Cao, Jian Fei Sun
Abstract: Al-10.5Zn-2.0Mg-1.5Cu alloy was produced by spray forming (SF) technique. The initial microstructure, particularly secondary phases, present in the as-SFed alloy was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with attached energy dispersive X-ray spectroscopy (EDS). The results indicated that the equiaxed α-Al grains have an average size of about 18-20 μm in diameter. The intergranular phase was identified as MgZn2 by selected area electron diffraction (SAED) pattern, which was also distributed in the grain interior as well as Al2Mg3Zn3. A needle-like Al23Cu(FeCrMn)4 precipitate was detected. The combined analysis of morphology and crystallographic structure suggested that the Al23Cu(FeCrMn)4 grew along its long axis of <001> orientation. The refinement of the intergranular phases occurred, which is probably due to a decreased amount of eutectic liquid phase finally solidifying on a large area of grain boundaries.
Authors: Marie Buffiere, Abdel Aziz El Mel, Nick Lenaers, Guy Brammertz, Armin E. Zaghi, Marc Meuris, Jef Poortmans
Abstract: Chalcopyrite ternary and kesterite quaternary thin films, such as Cu (In,Ga)(S,Se)2 and Cu2ZnSn (S,Se)4 generically referred to as CIGSSe and CZTSSe, respectively, have become the subject of considerable interest and study for semiconductor devices in recent years [1,2]. These materials are of particular interest for use as an absorber layer in photovoltaic devices. In thin film solar cells, the p-type CIGSSe or CZTSSe layer is combined with an n-type semiconductor thin film such as CdS buffer layer to form the p-n heterojunction of the device. The synthesis process of the CIGSSe or CZTSSe absorber layer requires temperatures ranging between 400 and 600 °C to form the photoactive chalcopyrite or kesterite phases [3,4]. During the synthesis process, the formation of trace amounts of binary/ternary compositions (i.e., undesirable secondary or impurity phases consisting of selenides, oxides, carbonates, etc.) may occur. These trace amounts of impurity phases may form at the nascent absorber surfaces, which could negatively affects the photovoltaic conversion efficiencies of solar cells [5-7]. Therefore, prior to the deposition of the CdS buffer layer, there is a need to clean the CIGSSe or CZTSSe surfaces to remove any possible traces of such impurities.
Authors: Kai Lin, Hong Qi Shi, Li Qun Ma, Yi Ding
Abstract: The properties and precipitation rules of secondary phases generated during isothermal aging of duplex stainless steels and factors affecting the precipitates were reviewed in this article. These secondary phases include carbides(M23C6,M7C3), nitrides(Cr2N,CrN) and intermetallic phases(σ-phase, χ-phase, Fe3Cr3Mo2Si2, R-phase, π-phase, α′-phase). With the right understanding about the phases, the aim is the suitable heat-treating processes would be chose to avoid the unfavorable influences of secondary phases.
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