scholarly journals Morphological Evolutions of Ni-Rich Phases in Al-Si Piston Alloys during 250–400 °C Thermal Exposure Processes

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5212
Author(s):  
Haowei An ◽  
Jiwei Geng ◽  
Zeyu Bian ◽  
Gen Liu ◽  
Mingliang Wang ◽  
...  
Keyword(s):  
Morphological Evolution ◽  
Morphological Characteristics ◽  
Hardness Test ◽  
Thermal Exposure ◽  
Micro Hardness ◽  
Morphological Transformation ◽  
Alloy Hardness ◽  
The Matrix ◽  
Hardness Increase ◽  
Exposure Process

The thermal stability of the Al-Si alloys during the thermal exposure process from 250 °C to 400 °C was systematically investigated. The relationships between the morphological evolution and the mechanical changes of the alloys were determined through the Vickers hardness test and materials characterization method. Initially, the alloys exhibited similar thermal degradation behavior. For example, the exposure process of the alloy at 300 °C can be divided into two stages according to the changes of the alloy hardness and the matrix micro-hardness. In detail, the first stage (0–2 h) exhibited a severe reduction of the alloy hardness while the second stage showed a more leveled hardness during the following 98 h. There are three identified morphological characteristics of Ni-rich phases in the alloy. Furthermore, the differences in both composition and the micro-hardness between these Ni-rich phases were confirmed. The underlying relationships between the morphological transformation of the Ni-rich phases and hardness fluctuation in the alloy were correlated and elucidated. The observed alloy hardness increase when the exposure temperature was 400 °C was unexpected. This behavior was explained from the perspectives of both Ni-rich phases evolution and dispersoid formation.

MICRO-HARDNESS AND WEAR-RESISTANCE INVESTIGATION IN CARBO-METAL COATING COMPOSITES OBTAINED THROUGH GAS-DETONATION METHOD

2020 ◽  
Vol 2020 (10) ◽  
pp. 29-36
Author(s):  
Ol'ga Sil'chenko ◽  
Marina Siluyanova ◽  
Petr Hopin
Keyword(s):  
Wear Resistance ◽  
Wear Intensity ◽  
Micro Hardness ◽  
Gas Detonation ◽  
Coating Application ◽  
The Matrix ◽  
Detonation Method ◽  
Hardness Increase ◽  
Quasi Crystals ◽  
Result Analysis

The work purpose consists in the investigation of carbometal coatings wear-resistance and micro-hardness depending on chemical structure of their components. The investigation object is carbide-metal coatings. The result analysis of comparative wear-resistance tests witnesses that with micro-hardness increase in metal carbides of compositions: Cr3C2, WC, TiC, TiCN, at a constant content of cladding metal (30…35mass %), a value of wear decreases according to the linear law. Wear intensity of coatings of clad carbide mixtures with different materials is defined to a certain extent with wear intensity of material added to the matrix. In the course of the work there were developed coating compositions reinforced with quasi-crystals, there is defined an optimum composition and modes of coating application with the gas-detonation method and their wear-resistance and micro-hardness were investigated.

Evaluation of the Resistance of Individual Si Die to Cracking

1998 ◽  
Author(s):  
R. Berriche ◽  
R.K. Lowry ◽  
M.I. Rosenfield
Keyword(s):  
Thermal Cycling ◽  
Hardness Test ◽  
Mechanical Stresses ◽  
Test Method ◽  
Processing Conditions ◽  
Micro Hardness ◽  
Test Methodology ◽  
Vickers Micro Hardness

Abstract The present work investigated the use of the Vickers micro-hardness test method to determine the resistance of individual die to cracking. The results are used as an indicator of resistance to failure under the thermal and mechanical stresses of packaging and subsequent thermal cycling. Indentation measurements on die back surfaces are used to determine how changes in wafer backside processing conditions affect cracks that form around impressions produced at different loads. Test methodology and results obtained at different processing conditions are discussed.

Micro-Hardness and Morphology of LDPE Influenced by Beta Radiation

2014 ◽  
Vol 606 ◽  
pp. 253-256 ◽  
Author(s):  
Martin Ovsik ◽  
Petr Kratky ◽  
David Manas ◽  
Miroslav Manas ◽  
Michal Stanek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Hardness Test ◽  
Polymer Materials ◽  
Beta Radiation ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Depth Sensing ◽  
Surface Layers ◽  
Hardness Values ◽  
Different Doses

This article deals with the influence of different doses of Beta radiation to the structure and mico-mechanical properties of Low-density polyethylene (LDPE). Hard surface layers of polymer materials, especially LDPE, can be formed by radiation cross-linking by β radiation with doses of 33, 66 and 99 kGy. Material properties created by β radiation are measured by micro-hardness test using the DSI method (Depth Sensing Indentation). Individual radiation doses caused structural and micro-mechanical changes which have a significant effect on the final properties of the LDPE tested. The highest values of micro-mechanical properties were reached at radiation dose of 66 and 99 kGy, when the micro-hardness values increased by about 21%. The changes were examined and confirmed by X-ray diffraction.

scholarly journals Investigation of the microstructure evolution in TP347HFG austenitic steel at 700°C and its characterization method

2021 ◽  
Vol 40 (1) ◽  
pp. 12-22
Author(s):  
Yuetao Zhang ◽  
Tingbi Yuan ◽  
Yawei Shao ◽  
Xiao Wang
Keyword(s):  
Austenitic Steel ◽  
Aging Time ◽  
Microstructure Evolution ◽  
Precipitate Phase ◽  
Dispersion Strengthening ◽  
Micro Hardness ◽  
Dispersed Particles ◽  
Nonlinear Ultrasonic ◽  
The Matrix ◽  
Solution Strengthening

Abstract This article reports the microstructure evolution in TP347HFG austenitic steel during the aging process. The experiments were carried out at 700°C with different aging time from 500 to 3,650 h. The metallographic results show that the coherent twin and incoherent twin are existed in the original TP347HFG grains, while they gradually vanished with the increase of the aging time. After aging for 500 h, a lot of fine, dispersed particles precipitated from the matrix, but they disappeared after aging for 1,500 h. When the aging time extend to 3,650 h, the precipitates appeared apparently coarse in TP347HFG steel, which include the M23C6 and σ phase; besides, the micro-hardness of TP347HFG also changes during the aging, which was closely related to the effect of dispersion strengthening and solution strengthening. The results of the nonlinear ultrasonic measurement reveal that the β′ of TP347HFG steel was also changed with the aging time. It first increased at 0–500 h, then reduced later, and increased finally at 1,500–3,650 h. The variation of β′ in TP347HFG was influenced by a combined effect of the twin microstructure and the precipitate phase, which indicate that the nonlinear ultrasonic technique can be utilized to characterize the microstructure evolution in TP347HFG.

Effects of microstructure and lattice misfit on creep life of Ni-based single crystal superalloy during long-term thermal exposure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenyan Gan ◽  
Hangshan Gao ◽  
Haiqing Pei ◽  
Zhixun Wen
Keyword(s):  
Single Crystal ◽  
Rupture Life ◽  
Precipitation Amount ◽  
Lattice Misfit ◽  
Thermal Exposure ◽  
Phase Evolution ◽  
Creep Rupture ◽  
Simultaneous Increase ◽  
Creep Life ◽  
The Matrix

Abstract According to the microstructural evolution during longterm thermal exposure at 1100 °C, the creep rupture life of Ni-based single crystal superalloys at 980 °C/270 MPa was evaluated. The microstructure was characterized by means of scanning electron microscopy, X-ray diffraction and related image processing methods. The size of γ’ precipitates and the precipitation amount of topologically close-packed increased with the increase in thermal exposure time, and coarsening of the γ’ precipitates led to the simultaneous increase of the matrix channel width. The relationship between the creep rupture life and the lattice misfit of γ/γ’, the coarsening of γ’ precipitate and the precipitation of TCP phase are systematically discussed. In addition, according to the correlation between γ’ phase evolution and creep characteristics during thermal exposure, a physical model is established to predict the remaining creep life.

The Influence of Ultrasonic Energy on Chemical Treatment of Surface Properties and the Properties of Composites Made of Luffa Cylindrical Fiber-Polyester Resin

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
E. Dilara Koçak
Keyword(s):  
Composite Structure ◽  
Polyester Resin ◽  
Unsaturated Polyester ◽  
Natural Fibers ◽  
Morphological Characteristics ◽  
Mechanical Tests ◽  
Cylindrical Fiber ◽  
The Matrix ◽  
Mechanical Performances ◽  
Properties Of Composites

Producing composites from natural fibers is known to be common. These fibers benefit from their mechanical performances, low density, and their biodegradability. However, it is necessary for the fibers to form adhesion in the matrix. Therefore, it is necessary to apply a chemical process to the surface of the fibers. In this study, four different processes in conventional and ultrasonic energies were applied on luffa cylindrical fibers. At the end of the application, a composite structure was formed on the fibers that were obtained by using unsaturated polyester resin. The changes in the characteristics of the composite structure were recorded by mechanical tests, Fourier transform infrared, X-ray diffractometer, and their morphological characteristics by means of scanning electron microscopy. Considering all the results, formic acid and acetic acid process results were found to adequately modify the fiber surfaces.

Detection of Compositional Fluctuations in High Temperature Exposed Waspaloy

2001 ◽  
Vol 699 ◽  
Author(s):  
Xiaodong Zou ◽  
Tariq Makram ◽  
Rosario A. Gerhardt
Keyword(s):  
Exposure Time ◽  
Structural Integrity ◽  
Thermal Exposure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gamma Prime ◽  
Distribution Shape ◽  
The Matrix ◽  
Quantitative Stereology ◽  
Nickel Base

AbstractWaspaloy is a nickel base super-alloy used in aircraft engines. When this alloy is placed in service, it is subjected to long term exposure at high temperatures, which can cause the reinforcing gamma prime precipitate population to fluctuate and thus affect its structural integrity. The population fluctuates as a result of coarsening, dissolution or re-precipitation. Samples exposed to 1200° F for times ranging from 0 to 12626 hours were characterized using impedance spectroscopy, microhardness measurements, x-ray diffraction and quantitative stereology. Two important parameters were derived from the impedance measurements: (1) the imaginary admittance peak magnitude (Ymax) and (2) the associated relaxation frequency (fmax). As the distribution, shape and size of the precipitates change with exposure time, these parameters were also found to vary. In addition to the changes in precipitate geometry, lattice constant changes detected by analyzing x-ray diffraction data suggest that there are compositional shifts in the matrix as well as the gamma prime precipitates. Furthermore, the preferred orientation of the precipitates can also be seen to change with exposure time. These changes in composition, size and shape as a function of thermal exposure time are accompanied by changes in the volume fractions of primary and secondary gamma prime particles present. Using effective medium models, it is possible to predict that the measured properties are related to the gamma prime population. The grain boundary carbides do not appear to play any role at the conditions presented.

Microstructural Stability and Lattice Misfit Characterisations of Nimonic 263

2012 ◽  
Author(s):  
Quanshun Luo ◽  
Kuangnan Chi ◽  
Shuxin Li ◽  
Pete Barnard
Keyword(s):  
Grain Boundary ◽  
Morphological Evolution ◽  
Lattice Misfit ◽  
Initial Growth ◽  
Microstructural Stability ◽  
Gaussian Peak ◽  
Hardening Treatment ◽  
The Matrix ◽  
Matrix Lattice ◽  
Average Size

Nimonic 263 has been selected as a candidate header/piping material of advanced ultra-supercritical (A-USC) boilers for the next generation of fossil fuel power plant. Experimental assessments on the microstructural stability of this material are presented in this paper. Microstructural evolution has been quantified by high resolution field emission SEM and TEM. Electron diffraction and the combined XRD and Gaussian peak-fitting have been applied to investigate the coherency and lattice misfit between the gamma prime (γ′) precipitates and the gamma (γ) matrix. The micro structure subjected to solution and hardening treatment consists of γ-matrix and a network of carbide precipitates along the grain boundaries. Large quantities of fine γ′-Ni3(Ti,Al) precipitates were observed, with an average size of 17 nm and coherent with the matrix lattice. The overall misfit has been quantified to be 0.28%. After long term aging at 700 and 725 °C for various periods up to 20,000 hours, γ′ was still the predominant precipitate and mostly coherent with the matrix. A few needle-shape η-Ni3Ti intermetallic precipitates were found in the grain boundary regions. The γ′ size has grown progressively to 78 nm, accompanied by the γ′-γ constrained misfit increasing to 0.50%. Moreover, the M23C6-type grain boundary carbides were found to have experienced morphological evolution, including the nucleation of Widmanstatten-type needles and their initial growth towards the matrix.

scholarly journals Character evolution of modern fly-speck fungi and implications for interpreting thyriothecial fossils

2020 ◽  
Author(s):  
Ludovic Le Renard ◽  
André L. Firmino ◽  
Olinto L. Pereira ◽  
Ruth A. Stockey ◽  
Mary. L. Berbee
Keyword(s):  
Morphological Evolution ◽  
Morphological Characters ◽  
Small Subunit ◽  
Leaf Surfaces ◽  
The Matrix ◽  
Character Matrix ◽  
Phylogenetic Framework ◽  
Single Hypha ◽  
Objective Basis ◽  
Ancestral Character States

AbstractPREMISE OF THE STUDYFossils show that fly-speck fungi have been reproducing with small, black thyriothecia on leaf surfaces for ∼250 million years. We analyze morphological characters of extant thyriothecial fungi to develop a phylogenetic framework for interpreting fossil taxa.METHODSWe placed 59 extant fly-speck fungi in a phylogeny of 320 Ascomycota using nuclear ribosomal large and small subunit sequences, including newly determined sequences from nine taxa. We reconstructed ancestral character states using BayesTraits and maximum likelihood after coding 11 morphological characters based on original observations and literature. We analyzed the relationships of three previously published Mesozoic fossils using parsimony and our morphological character matrix, constrained by the molecular phylogeny.KEY RESULTSThyriothecia evolved convergently in multiple lineages of superficial, leaf- inhabiting ascomycetes. The radiate and ostiolate scutellum organization is restricted to Dothideomycetes. Scutellum initiation by intercalary septation of a single hypha characterizes Asterinales and Asterotexiales, and initiation by coordinated growth of two or more adjacent hyphae characterizes Aulographaceae (order incertae sedis). Scutella in Microthyriales are initiated apically on a lateral hyphal branch. Patterns of hyphal branching in scutella contribute to distinguishing among orders. Parsimony resolves three fossil taxa as Dothideomycetes; one is further resolved as a member of a Microthyriales-Zeloasperisporiales clade within Dothideomycetes.CONCLUSIONSThis is the most comprehensive systematic study of thyriothecial fungi and their relatives to date. Parsimony analysis of the matrix of character states of modern taxa provides an objective basis for interpreting fossils, leading to insights into morphological evolution and geological ages of Dothideomycetes clades.

scholarly journals Characterization of Enamel After the Use of Oral Hygiene Auxiliaries with Whiteners

2019 ◽  
pp. 227-236
Author(s):  
Norma Verónica Zavala-Alonso DDS, MSc, PhD ◽  
Jorge Humberto Ramírez-González DDS, MSc ◽  
Mariana Ramírez-Vergara DDS ◽  
José Gilberto Roque-Márquez DDS, MSc ◽  
Flores Daniel Silva-Herzog DDS, MSc, PhD
Keyword(s):  
Oral Hygiene ◽  
Dental Enamel ◽  
Hardness Test ◽  
Study Groups ◽  
Micro Hardness ◽  
Sem Images ◽  
Group 4 ◽  
Group 2 ◽  
Mouth Wash ◽  
Group 1

The purpose of this study was to evaluate the effect of the use of the combined auxiliaries of oral hygiene with whitening agents on the micro-hardness and micro-morphology of dental enamel. Materials and Methods. 40 human incisors were used and sectioned to obtain 4x4mm samples and divided into four study groups. Group 1: Electric brushing with Toothpaste (BTP); Group 2: Electric brushing with Toothpaste+mouthwash (BTP+MW); Group 3: Electric brushing with Toothpaste+whitening pen (BTP+WP); Group 4: Electric brushing with Toothpaste+mouth wash+whitening pen (BTP+MW+WP). Samples were submitted toVickers micro-hardness test and visualized using scanning electron microscopy (SEM). Results. All groups, with the exception of group 1, showed a decrease in micro-hardness values after applying the treatments (p<0.05). Likewise, when comparing the values after the treatments between the groups, significant statistical differences were found in all of comparisons except for those of groups 2 and 4. SEM images showed changes in the morphology in all the study groups with the exception of group 1. Conclusion. Significant changes such as decrease in micro-hardness as well as in the topography of the enamel surface such as elevations, craters, porosities and etching patterns were founded after the use of the combination of auxiliaries of oral hygiene with whitening agents.  

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