AEM characterization of SiC fiber/AIN composites

1994 ◽  
Vol 52 ◽  
pp. 630-631
Author(s):  
K. Park ◽  
C. Sung
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Creep Tests ◽  
Cross Sectional ◽  
Sintering Aid ◽  
Sic Fiber ◽  
Vacuum Atmosphere ◽  
The Matrix ◽  
Convergent Beam

SiC fiber (15 vol. %)/AlN composites were fabricated by hot pressing at 1650°C and 17.6 MPa using a 4Ca(OH)2·Al2O3 sintering aid under vacuum atmosphere. Creep tests for the composites were conducted at compressive stress of 50 MPa and at 1120°C for 48 hours under oxygen atmosphere. Cross-sectional TEM samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector. Selected area diffraction (SAD), convergent beam electron diffraction (CBED), and energy dispersive X-ray spectroscopy (EDXS) were used to identify the microstructure and microchemistry of the matrix, fiber, and matrix/fiber interface of the composites.Generally, the AIN matrix contained a liquid phase at grain boundaries and a high density of dislocations within the grains (Fig. 1(a)). Most of the additives were present at the grain boundaries. Fig. 1(b) shows a SAD pattern from the liquid phase at the grain boundaries. The liquid phase was identified as Ca12Al14O33 with a cubic structure (a = 1.198 nm).

Microstructural characterization of a SiC Whisker-Reinforced HIPped Reaction-Bonded Si3N4

1988 ◽  
Vol 120 ◽  
Author(s):  
S. C. Farmer ◽  
P. Pirouz ◽  
A. H. Heuer
Keyword(s):  
Grain Boundaries ◽  
Glassy Phase ◽  
Microstructural Characterization ◽  
Core Region ◽  
Sintering Aid ◽  
The Core ◽  
Composite Fabrication ◽  
The Matrix ◽  
Sic Whiskers

AbstractA SiC whisker reinforced HIPped RBSN material fabricated with a Y2O3 sintering aid was characterized using TEM. The matrix is > 90% β-Si3 N4 with a Y-Si-O-N glassy phase at the Si3 N4 grain boundaries and about the SiC whiskers. The SiC whisiers are heavily faulted and have a well defined core. Si3 N4 precipitates are observed in the core region after composite fabrication. A preliminary mechanism for the growth of the SiC whisker, based on the VLS mechanism is proposed.

TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

1988 ◽  
Vol 46 ◽  
pp. 738-739
Author(s):  
G. Das ◽  
R. E. Omlor
Keyword(s):  
Titanium Alloys ◽  
Reaction Zone ◽  
Carbon Layer ◽  
Fiber Reinforced ◽  
Reaction Products ◽  
Sic Fibers ◽  
Sic Fiber ◽  
The Matrix ◽  
Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

scholarly journals Mechanical and Fractographical Characterization of Extruded Al-Mg-Si-Zr Alloys

2018 ◽  
Vol 188 ◽  
pp. 02017
Author(s):  
Fulya Kahrıman ◽  
Muzaffer Zeren
Keyword(s):  
Fracture Behavior ◽  
Direct Chill ◽  
Grain Structure ◽  
Tensile Fracture ◽  
Casting Method ◽  
Cross Sectional ◽  
Fracture Surfaces ◽  
The Matrix ◽  
Zr Alloys

In this study, the chemical composition of Al-0.8Mg-0.8Si alloys was modified with the addition of 0.1 and 0.2 wt.-% Zr. The billets were manufactured by direct chill casting method, homogenized at 560 °C for 6h and then extruded in order to obtain profiles having hollow and circular sections. Recrystallization layer (shell) became narrower due to the addition of Zr. This was attributed to the formation of very fine precipitates (Al3Zr) within the matrix. The mechanical properties showed that both yield and tensile strengths increased as a function of Zr content. Tensile fracture surfaces were examined by scanning electron microscope and the fractographs reflected the effect of grain structure on the fracture behavior of studied alloys. All fracture surfaces indicated typical dimple ruptures, however, the size of dimples were observed as finer structures as a function of Zr content. As seen in cross-sectional graphs, as the Zr content increased the grain structure was refined due to Al3Zr precipitates. These fine precipitates caused the formation of fine and shallow dimples under loading.

The characterization of an SCS6/Ti–6Al–4V MMC interphase

1989 ◽  
Vol 4 (2) ◽  
pp. 327-335 ◽  
Author(s):  
C. Jones ◽  
C. J. Kiely ◽  
S. S. Wang
Keyword(s):  
Metal Matrix ◽  
Chemical Interaction ◽  
Auger Spectroscopy ◽  
Carbon Layer ◽  
Convergent Beam Electron Diffraction ◽  
Interphase Region ◽  
The Matrix ◽  
Convergent Beam

Using TEM, Auger spectroscopy, EDX, and convergent beam electron diffraction, a thorough characterization of the interphase region between SCS6 fibers and Ti–6Al–4V matrix in a metal matrix composite has been performed. The interphase region is shown to be very complex, consisting of numerous layers of varying compositions and thicknesses. The chemical interaction of the fiber and matrix results in a 0.5–1.5 μm thick TiC layer. Evidence for the existence of a Tix Siy (C) layer is also presented. The SCS6 overlayer on the fibers has inhibited any chemical interaction between the matrix and the SiC filament itself, 60% of the interphase region originating from the SCS6 protective coating. In situ fracture experiments (in an Auger spectrometer) reveal that fracture takes place between the TiC and an amorphous carbon layer.

scholarly journals Influence of the Base Element on the Thermal Properties of Non- Ferrous Chromium-Rich TaC-Containing Alloys Elaborated by Conventional Casting: Part 3: Surface and Cross-Sectional Metallographic Characterization of the Oxidized Alloys

2019 ◽  
Vol 6 ◽  
Author(s):  
Jean-Paul K. Gomis ◽  
Patrice Berthod ◽  
Erwann Etienne
Keyword(s):  
Thermal Properties ◽  
Isothermal Oxidation ◽  
Population Characteristics ◽  
Cross Sectional ◽  
Base Element ◽  
Free Zone ◽  
The Matrix ◽  
Oxide Spallation ◽  
First Time

The six alloys the thermal properties of which and the tendency to oxide spallation of which were studied in the first two parts of this work, were here characterized after oxidation for 70 hours at 1250°C. The external chromia scale, and also the CrTaO4 subsurface oxide, formed for all the alloys, almost independently of the Co and Ni proportions in the base element content. But, because of the formation of more CrTaO4 for the nickel-richest alloys probably due to the higher availability of Ta in the matrix and its easier diffusion towards the neighbourhood of the oxidation front, the adherence of chromia was weakened and spallation, suggested by the thermogravimetric curves in the second part of this work, is here really observed and the denuded part of alloys clearly seen. The degradation of the subsurface, which can be in a first time summarized by the development of a carbide-free zone and a {Cr, Ta}-depleted zone, depends on the Co and Ni proportions. The microstructure of the bulk is differently affected by long exposure at elevated temperature. The changes in carbide population characteristics are stronger for the nickel-based alloys than for the cobalt-based ones. Finally, the isothermal oxidation behaviour is best for the nickel-richest alloys but the oxide spallation behaviour and the potential mechanical properties are the best for the cobalt-richest alloys.

Processing and characterization of YBCO grain boundaries obtained by the liquid phase removal method

1998 ◽  
Vol 53 (1-2) ◽  
pp. 32-37 ◽  
Author(s):  
K. Salama ◽  
S. Sathyamurthy ◽  
G. Du ◽  
M. Miranova
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Removal Method

Liquid-phase sintering of BN doped Fe-Cu/TiC composites

1996 ◽  
Vol 54 ◽  
pp. 666-667
Author(s):  
Nuri Durlu ◽  
Nan Yao ◽  
David L. Milius ◽  
Ilhan A. Aksay
Keyword(s):  
Wear Resistance ◽  
Liquid Phase ◽  
Hot Pressing ◽  
Liquid Phase Sintering ◽  
Electron Microscopic ◽  
Hard Particles ◽  
Cu Alloys ◽  
The Matrix ◽  
Full Densification

Fe-Cu composites are commonly produced by liquid phase sintering (above the melting temperature of Cu, 1085°C). The wear resistance of these Fe-Cu alloys can be enhanced by introducing hard particles, e.g., TiC, into the matrix. In such cases, however, the densification of Fe-Cu/TiC composites by liquid phase sintering becomes difficult mainly due to the high wetting angle (110° at 1100-1200°C in argon) of liquid Cu with TiC particles. Especially when the amount of the TiC phase is high enough to form a continuous network of TiC grains, full densification is only achieved through hot pressing. We have recently overcome this problem in an [(Fe-4 wt% Cu) + 30 wt% TiC] composite by the addition of small amounts of BN. Composites with BN additives have been successfully sintered at 1275°C under vacuum or argon by additions of 1 wt% BN. Electron microscopic characterization of these composites has shown that this success is due to the modification of the liquid phase by the addition of BN, which also promotes the liquid phase sintering of the TiC phase.

Role of matrix microstructure in the ultrasonic characterization of fiber-reinforced metal matrix composites

1997 ◽  
Vol 12 (3) ◽  
pp. 754-763 ◽  
Author(s):  
S. Krishnamurthy ◽  
T. E. Matikas ◽  
P. Karpur
Keyword(s):  
Titanium Alloy ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Matrix Composites ◽  
Fiber Reinforced ◽  
Matrix Microstructure ◽  
Sic Fiber ◽  
The Matrix ◽  
Ultrasonic Images

This work deals with the application of ultrasonic nondestructive evaluation for characterizing fiber-reinforced metal matrix composites. The method involved the use of a recently developed technique in which the fiber reinforcement acts as a reflector to incident ultrasonic shear waves. Single fiber and multifiber, single ply composites consisting of SiC fibers in several titanium alloy matrices were investigated. The ultrasonic images obtained were correlated with the results of metallographic characterization of the composites. The results showed that the ultrasonic response of the metal matrix composites is significantly influenced by the microstructure of the matrix through which the incident wave traverses. The general effects of matrix on ultrasonic wave propagation are reviewed, and the ultrasonic signals obtained from various SiC fiber-reinforced titanium alloy composites are discussed in terms of the scattering effects of matrix microstructure.

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