scholarly journals Effects of Intermetallic Microstructure on Degradation of Mg-5Nd Alloy

2020 ◽  
Vol 51 (10) ◽  
pp. 5498-5515 ◽  
Author(s):  
Yaping Zhang ◽  
Yuanding Huang ◽  
Frank Feyerabend ◽  
Sarkis Gavras ◽  
Yuling Xu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundaries ◽  
Culture Conditions ◽  
Product Layer ◽  
Heat Treated Sample ◽  
Corrosion Propagation ◽  
Heat Treated ◽  
Treated Sample ◽  
The Matrix ◽  
Immersion Testing

Abstract The influence of intermetallic microstructure on the degradation of Mg-5Nd alloy with different heat treatments was investigated via immersion testing in DMEM + 10 pct FBS under cell culture conditions and subsequent microstructural characterizations. It was found that T4 heat-treated sample had the poorest corrosion resistance due to the lack of finely dispersed precipitates inside grains, continuous lamellar particles along grain boundaries and outer Ca-P layer, and to the formation of a loose corrosion product layer. In contrast, the aged samples exhibited a better corrosion resistance due to their presence and to the formation of a compact corrosion layer. Their degradation behavior largely depended on the intermetallic microstructure. Corrosion was initiated in the matrix around stable globular particles Mg41Nd5 at grain boundaries. In the sample aged at high temperature 245 °C, the coexistence of lamellar Mg41Nd5 particles and their nearby Nd-poor regions enhanced the corrosion. The corrosion first started in such regions. It was shown that those finely dispersed precipitates formed during aging had no influence on the corrosion initiation. However, they indeed affected the subsequent corrosion propagation with the immersion proceeding. They supplied barriers for corrosion propagation and hence were beneficial for improving the corrosion resistance. The continuously distributed lamellar Mg41Nd5 precipitates formed at grain boundaries during aging at 245 °C supplied an additional effective obstacle to corrosion propagation. This was especially beneficial for hindering the corrosion propagation at the later stage of corrosion.

Formation of Ti-Matrix Composites for Lightweight Structural Components by Mechanical Alloying and Subsequent Annealing

2006 ◽  
Vol 514-516 ◽  
pp. 609-613 ◽  
Author(s):  
Bruno Trindade ◽  
Marco Caetano ◽  
Nelson Duarte
Keyword(s):  
Solid Solution ◽  
Mechanical Alloying ◽  
Matrix Composites ◽  
Structural Components ◽  
Mechanically Alloyed ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
The Matrix ◽  
Matrix Hardness

In this work, a lightweight Ti-10Mg-5Al (wt. %) alloy for structural components was produced by mechanical alloying. A metastable α-Ti(Al,Mg) solid solution was obtained after 50h of milling. Diffraction peaks ascribed to the Mg phase were detected in the XRD pattern of the sample heat treated at 600°C. This phase tends to oxidize with the increase of temperature giving rise to MgO. The structure of the mechanically alloyed and 900°C heat treated sample consisted of a Ti(Al) solid solution with dispersed MgO particles in the matrix. Hardness and Young’s modulus values obtained from ultramicrohardness tests confirm the strength improvement of the Ti-based alloy due to the MgO reinforcement.

Effect of Cr Plating and Plasma Nitriding on Hardness and Corrosion Resistance of H13 Steel

2014 ◽  
Vol 1025-1026 ◽  
pp. 737-744
Author(s):  
Lertjirakul Tanakorn ◽  
Yuttanant Boonyongmaneerat ◽  
Visuttipitukul Patama
Keyword(s):  
Corrosion Resistance ◽  
Thin Layer ◽  
Surface Characterization ◽  
Plasma Nitriding ◽  
Surface Hardness ◽  
H13 Steel ◽  
Heat Treated Sample ◽  
Improve Corrosion Resistance ◽  
Heat Treated ◽  
Treated Sample

H13 steel has been widely used in several metal working industries. Plasma nitriding is employed for improving surface hardness, but it significantly decreases corrosion resistance of H13 steel. To improve corrosion resistance, Cr plating before and after plasma nitriding is studied in the research. Surface characterization, phase analysis, hardness and corrosion test were done to evaluate the appropriate method to improve corrosion resistance. It was found that Cr plating after plasma nitriding can improve the corrosion resistance close to as-heat treated sample. The formation of Cr can increase the corrosion potential to-310.66 mV(Ag-AgCl) comparing to-349.54 mV(Ag-AgCl) of as-heat treated sample. For the corrosion resistance at constant applied voltage tested by potentiostatic technique, the sample with plasma nitriding prior to Cr plating shows the lowest corrosion current which implies the lowest corrosion rate. For the process in which Cr plating is applied before plasma nitriding, CrN layer can be formed on the surface, but this layer is very thin (about 100 nm thick). This thin layer retards nitrogen diffusion; hence, nitrided layer beneath CrN layer cannot be formed. With only thin layer of CrN, both corrosion resistance and micro-scale surface hardness cannot be improved.

Enhanced Hydrolytic Stability of Porous Boron Nitride via the Control of Crystallinity, Porosity and Chemical Composition

2018 ◽  
Author(s):  
Ravi Shankar ◽  
Sofia Marchesini ◽  
Camille Petit
Keyword(s):  
Boron Nitride ◽  
Hydrolytic Stability ◽  
Chemical Properties ◽  
Spectroscopic Techniques ◽  
High Porosity ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
Molecular Separations ◽  
High Degree

Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or a controlled stability) over a range of chemical environments, and particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical-chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample exhibits enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures, and will progress the implementation of the material in applications involving interfacial phenomena.<br>

Surface Treatments of Stainless Steel by Electroless Silver Coatings as a Bipolar Plate for Proton Exchange Membrane Fuel Cells

2015 ◽  
Vol 12 (6) ◽  
Author(s):  
Ing-Bang Huang ◽  
Ching Chiang Hwang
Keyword(s):  
Corrosion Resistance ◽  
Fuel Cell ◽  
Current Density ◽  
Corrosion Current Density ◽  
Proton Exchange Membrane ◽  
Corrosion Current ◽  
Proton Exchange ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Exchange Membrane

The objective of this study is to examine the effect of heat treatment at various temperatures on the corrosion behavior of electroless silver-coated SS 304 in a simulated proton exchange membrane (PEM) fuel cell environment. The corrosion properties of this material were studied using a potentiodynamic polarization technique. X-ray diffraction (XRD) patterns, polarization curves, and scanning electron microscopy (SEM) of coated and heat-treated specimens obtained in various heating temperatures were also utilized. It was found that the corrosion potential of the coated and heat-treated specimens shift toward a noble potential, and a significant decrease in corrosion current density was also observed. The corrosion current density decreased by a factor of about 1/500 for the heat-treated sample of 600 °C compared to the substrate. The heat-treated specimens displayed greater corrosion resistance than unheated and bare ones. According to the polarization studies and SEM images, the heat-treated specimen at 600 °C shows excellent corrosion resistance with a homogeneous dense surface morphology. These results demonstrated the coatings were suited for fuel cell applications in the proton exchange membrane fuel cell (PEMFC) environment.

Research on Fluctuations in Work Hardening Rate of a Fe-Mn-Al-C Steel

2015 ◽  
Vol 817 ◽  
pp. 288-292 ◽  
Author(s):  
Chao Zhao ◽  
Ren Bo Song ◽  
Lei Feng Zhang ◽  
Fu Qiang Yang ◽  
Shuai Qin
Keyword(s):  
Electron Microscopy ◽  
Work Hardening ◽  
True Strain ◽  
Rate Curve ◽  
Heat Treated Sample ◽  
Transmission Electron ◽  
Heat Treated ◽  
Treated Sample ◽  
Fluctuation Range ◽  
Work Hardening Rate

The fluctuations in the work hardening rate of a Fe-12Mn-10Al-0.7C (wt. %) steel have been investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The work hardening rate of the heat treated sample had a tendency of decrease with fluctuations. The first raise in the work hardening rate curve at about 2% true strain is attributed to the shearing of the small ferrite grains by austenite, and the deformation induced twinning can contribute to the raise and drop in the work hardening rate curve. The second fluctuation range at the true strain between 10% and 14% is mainly related to the activation of planar slip on the principle slip plane which is suppressed by twins in austenite.

Microstructure and Properties of Heat-Treated 440C Martensitic Stainless Steel

2013 ◽  
Vol 334-335 ◽  
pp. 105-110 ◽  
Author(s):  
Siti Hawa Mohamed Salleh ◽  
Mohd Nazree Derman ◽  
Mohd Zaidi Omar ◽  
Junaidi Syarif ◽  
S. Abdullah
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Stainless Steel ◽  
Martensitic Stainless Steel ◽  
Ferrite Matrix ◽  
Rapid Quenching ◽  
Heat Treated Sample ◽  
Treatment Processes ◽  
Heat Treated ◽  
Treated Sample

440C martensitic stainless steels are widely used because of their good mechanical properties. The mechanical properties of 440C martensitic stainless steel were evaluated after heat treatment of these materials at various types of heat treatment processes. The initial part of this investigation focused on the microstructures of these 440C steels. Microstructure evaluations from the as-received to the as-tempered condition were described. In the as-received condition, the formations of ferrite matrix and carbide particles were observed in this steel. In contrast, the precipitation of M7C3carbides and martensitic structures were present in this steel due to the rapid quenching process from the high temperature condition. After precipitation heat treatment, the Cr-rich M23C6carbides were identified within the structures. Moreover, a 30 minutes heat-treated sample shows the highest value of hardness compared to the others holding time. Finally, the tempering process had been carried out to complete the whole heat treatment process in addition to construct the secondary hardening phenomenon. It is believed that this phenomenon influenced the value of hardness of the 440C steel.

Thermal Conductivity of Heat Treated and Non-Heat Treated Individual Multiwalled Carbon Nanotubes

2011 ◽  
Author(s):  
Michael F. P. Bifano ◽  
Pankaj B. Kaul ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Multiwalled Carbon ◽  
Heat Treated Sample ◽  
Heat Treated ◽  
Treated Sample ◽  
Annealing Heat Treatment

Thermal conductivity measurements of commercially available CVD grown individual multiwalled carbon nanotubes (MWCNTs) are reported. The measurements are performed using the three-omega-based Wollaston T-Type probe method inside a scanning electron microscope (SEM). An average 385% increase in thermal conductivity is measured for those MWCNTs samples which undergo a 20 hour 3000°C post annealing heat treatment. However, in most samples qualitatively characterized defects are found to negate any advantage of the heat treatment process. The highest thermal conductivity measured is 893.0 W/mK and is of a heat-treated sample. These results will help to improve the quality of MWCNT production and aid in the development of highly efficient CNT-structured thermal management devices and engineering materials.

scholarly journals White-Ceramic Conversion on Ti-29Nb-13Ta-4.6Zr Surface for Dental Applications

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Akiko Obata ◽  
Eri Miura-Fujiwara ◽  
Akimitsu Shimizu ◽  
Hirotaka Maeda ◽  
Masaaki Nakai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Pure Titanium ◽  
Average Roughness ◽  
Heat Treated Sample ◽  
Cell Compatibility ◽  
Heat Treated ◽  
Treated Sample ◽  
Mouse Osteoblast ◽  
Cp Ti

Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy has excellent mechanical properties and bone conductivity. For dental application, TNTZ surfaces were converted to white oxidized layer by a simple heat treatment in air to achieve the formation of aesthetic surfaces. The oxidized layer formed by the heat treatment at 1000°C for 0.5 or 1 hr was whiter and joined to TNTZ substrate more strongly than that formed by the treatment at 900°C. The layer consisted of TiO2(rutile), TiNb2O7, and TiTa2O7and possessed ~30 μm in thickness for the sample heat-treated at 1000°C and ~10 μm for that heat-treated at 900°C. The surface average roughness and the wettability increased after the heat treatment. The spreading and proliferation level of mouse osteoblast-like cell (MC3T3-E1 cell) on the heat-treated sample were almost the same as those on as-prepared one. The cell spreading on TNTZ was better than those on pure titanium (CP Ti) regardless of the heat treatment for the samples. There was no deterioration in thein vitrocell compatibility of TNTZ after the oxidized layer coating by the heat treatment.

Evolution of Oxide Particles during Fabrication Processes of 12Cr ODS Steel

2012 ◽  
Vol 1383 ◽  
Author(s):  
Xiaodong Mao ◽  
Tae Kyu Kim ◽  
Sung-Soo Kim ◽  
Chang Hee Han ◽  
Kyu Hwan Oh ◽  
...  
Keyword(s):  
Hot Rolling ◽  
Rolling Process ◽  
Face Centered Cubic ◽  
Metal Powders ◽  
Heat Treated Sample ◽  
Ods Steel ◽  
Treated Sample ◽  
The Matrix ◽  
Oxide Particles ◽  
Face Centered

ABSTRACT12Cr ODS steel samples were prepared by mechanical alloying of the metal powders with 20-30 nm Y2O3 particles followed by isostatic pressing, hot rolling and final heat treatment. Evolutions of oxide particles such as YTaO4 and YCrO3 after each fabrication step were investigated by using TEM with EDS. Crystallographic correlation between oxide particles and the matrix was investigated in a HIPped sample, and interactions between dislocations and oxide particles were observed in hot rolled or heat treated sample. Size distributions of oxide particles were measured by carbon replica samples and it was found that coarsening of oxide particles from 9 to 12 nm occurred during hot rolling process. Additional isothermal annealing at 1250 ˚C revealed that phase transformation of oxide particles from monoclinic YTaO4 to face centered cubic Y3TaO7 was observed.

SHOCK COMPACTION OF Gd-DOPED CERIA CERAMICS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1686-1691 ◽  
Author(s):  
HA NEUL KIM ◽  
DO KYUNG KIM ◽  
SOON NAM CHANG ◽  
NARESH N. THADHANI
Keyword(s):  
Sintering Behavior ◽  
Doped Ceria ◽  
Shock State ◽  
Heat Treated Sample ◽  
Gas Gun ◽  
Nano Powder ◽  
Shock Compaction ◽  
Heat Treated ◽  
Treated Sample ◽  
Recovered Sample

Gd -doped ceria nano powder(~5 nm) was shock-loaded by a plate impact experiment using a single stage light gas gun. A computational model was used to simulate the shock state (pressure and density changes along time) of the sample in two dimensional Eulerian code. The predicted density of compacted sample from the simulation was about 90%. To reveal the effect of shock compaction on sintering behavior, the recovered sample was heat-treated and the microstructure was compared with that of a conventionally compacted and heat-treated sample.

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