scholarly journals Mechanism Of Ductile Rupture In The AL/Sapphire System Elucidated Using X-Ray Tomographic Microscopy

1995 ◽  
Vol 409 ◽  
Author(s):  
Wayne E. King ◽  
Geoffrey H. Campbell ◽  
David L. Haupt ◽  
John H. Kinney ◽  
Robert A. Riddle ◽  
...  
Keyword(s):  
Void Growth ◽  
Fracture Mechanism ◽  
Crack Extension ◽  
Initial Crack ◽  
Fracture Mechanisms ◽  
Second Phase ◽  
Metal Foil ◽  
Ductile Rupture ◽  
X Ray ◽  
Second Phase Particles

AbstractThe fracture of a thin metal foil constrained between alumina or sapphire blocks has been studied by a number of investigators. The systems that have been investigated include Al [1,2], Au [3], Nb [4], and Cu [5]. Except for Al/ Al2O3 interfaces, these systems exhibit a common fracture mechanism: pores form at the metal/ceramic interface several foil thicknesses ahead of the crack which, under increasing load, grow and link with the initial crack. This mechanism leaves metal on one side of the fracture surface and clean ceramic on the other. This has not been the observation in Al/ A12O3 bonds where at appropriate thicknesses of Al, the fracture appears to proceed as a ductile rupture through the metal.The failure of sandwich geometry samples has been considered in several published models, e.g., [6,71. The predictions of these models depend on the micromechanic mechanism of crack extension. For example, Varias et al. proposed four possible fracture mechanisms: (i) near-tip void growth at second phase particles or interfacial pores and coalescence with the main crack, (ii) high-triaxiality cavitation, i.e., nucleation and rapid void growth at highly stressed sites at distances of several layer thicknesses from the crack tip, (iii) interfacial debonding at the site of highest normal interfacial traction, and (iv) cleavage fracture of the ceramic. Competition among the operative mechanisms determines which path will be favored.This paper addresses the question of why the fracture of the A1/A12O3 system appears to be different from other systems by probing the fracture mechanism using X-ray tomographic microscopy (XTM). We have experimentally duplicated the simplified geometry of the micromechanics models and subjected the specimens to a well defined stress state in bending. The bend tests were interrupted and XTM was performed to reveal the mechanism of crack extension.

Effects of a second phase on the impact strength of structural steels

1978 ◽  
Vol 36 (1) ◽  
pp. 604-605
Author(s):  
T. Gréday ◽  
H. Mathy
Keyword(s):  
Fracture Mechanisms ◽  
Second Phase ◽  
Cleavage Crack ◽  
X Ray ◽  
Steel Microstructure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Second Phase Particles ◽  
Second Phases ◽  
The Impact

Both steel producers and users are faced with the problem of evaluating steel toughness. This property depends on the steel microstructure and, more particularly, on the presence of second phase particles. Consequently is important the knowledge of how fracture mechanisms are related to those particles. Also, quantitative relationships between second phase particles and properties are requested. Results have been obtained using a SEM equipped with peripherals. X-ray spectrometers and image analysis (1,2) as well as a TEM working on thin foils. Studied second phases range from microprecipitates in HSLA steels to coarser particles such as : inclusions, cementite, pearlite and bainite or martensite islands. In each case, characterization has been attempted of their size, shape, nature and distribution. Toughness is defined by transition temperatures or by shelf energy. Pearlite islands can initiate, stop or deflect a local crack. Deflection brings into relief 2 facets of the pearlite island when it deflects a cleavage crack originated by 2 adjacent grains (Fig.l).

Analytical Electron Microscopy Study of Second-Phase Particles in 7075 and 7475 Aluminum Alloys

1985 ◽  
Vol 43 ◽  
pp. 348-349
Author(s):  
M. Raghavan ◽  
J. Y. Koo ◽  
J. W. Steeds ◽  
B. K. Park
Keyword(s):  
Aluminum Alloys ◽  
Silicon Oxide ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Partial Substitution ◽  
Second Phase ◽  
X Ray ◽  
Second Phase Particles ◽  
Almost All

X-ray microanalysis and Convergent Beam Electron Diffraction (CBD) studies were conducted to characterize the second phase particles in two commercial aluminum alloys -- 7075 and 7475. The second phase particles studied were large (approximately 2-5μm) constituent phases and relatively fine ( ∼ 0.05-1μn) dispersoid particles, Figures 1A and B. Based on the crystal structure and chemical composition analyses, the constituent phases found in these alloys were identified to be Al7Cu2Fe, (Al,Cu)6(Fe,Cu), α-Al12Fe3Si, Mg2Si, amorphous silicon oxide and the modified 6Fe compounds, in decreasing order of abundance. The results of quantitative X-ray microanalysis of all the constituent phases are listed in Table I. The data show that, in almost all the phases, partial substitution of alloying elements occurred resulting in small deviations from the published stoichiometric compositions of the binary and ternary compounds.

Nanoscale Three-Dimensional Microstructural Characterization of an Sn-Rich Solder Alloy Using High-Resolution Transmission X-Ray Microscopy (TXM)

2016 ◽  
Vol 22 (4) ◽  
pp. 808-813 ◽  
Author(s):  
Chandrashekara S. Kaira ◽  
Carl R. Mayer ◽  
V. De Andrade ◽  
Francesco De Carlo ◽  
Nikhilesh Chawla
Keyword(s):  
Fresnel Zone ◽  
Three Dimensional ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Full Field ◽  
X Ray ◽  
Second Phase Particles ◽  
Rich Alloy ◽  
Nanoscale Features

AbstractThree-dimensional (3D) nondestructive microstructural characterization was performed using full-field transmission X-ray microscopy on an Sn-rich alloy, at a spatial resolution of 60 nm. This study highlights the use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure. The 3D reconstruction was also used to quantify microstructural details of the analyzed volume.

scholarly journals A Microstructure Investigation of the Deformation and Recrystallization of Particle-Containing Aluminium-Silicon Alloys

1993 ◽  
Vol 20 (1-4) ◽  
pp. 125-140 ◽  
Author(s):  
F. Habiby ◽  
F. J. Humphreys
Keyword(s):  
Single Crystals ◽  
Recrystallization Texture ◽  
Rolling Texture ◽  
Plasticity Theory ◽  
Second Phase ◽  
Slip Systems ◽  
Deformation Bands ◽  
Silicon Alloys ◽  
X Ray ◽  
Second Phase Particles

Single crystals and polycrystals of aluminium containing non-deformable second-phase particles of silicon, have been deformed, and the resultant structures investigated by microscopy and by X-ray and microtexture techniques. The particle size is found to influence the scale of the deformation bands formed, and there is evidence that particles may affect the nucleation of these bands. The deformed materials were recrystallized, and the effect of particle stimulated nucleation on the weakening of the rolling texture is discussed with reference to a computer simulation. In contrast, the recrystallization texture of particle-containing single crystals deformed on only two slip systems is sharp, and it is shown that the texture components are consistent with plasticity theory.

Fracture mechanics in design and service: ‘living with defects’ - Metallurgical aspects of the toughness of engineering alloys

1981 ◽  
Vol 299 (1446) ◽  
pp. 45-57 ◽  
Keyword(s):  
Tensile Stress ◽  
Crack Extension ◽  
Failure Modes ◽  
Fatigue Loading ◽  
Second Phase ◽  
Cleavage Crack ◽  
Factors Associated ◽  
Second Phase Particles ◽  
Engineering Alloys ◽  
Growth Of Voids

The paper treats micro-mechanical modes of crack extension, classed as ‘cracking’ and ‘rupture’ processes. In ‘cracking’, a cleavage crack nucleus propagates when a critical local tensile stress is attained, the magnitude of the stress being determined by the microstructure. Models for crack propagation from carbides and from martensite/ bainite ‘packets’ are discussed. The ‘rupture’ processes involve the initiation and growth of voids, centred on second-phase particles. Coalescence may arise from ‘internal necking’ or ‘fast shear’ and the factors associated with these two modes are described. Consideration is also given to the ways in which microstructure may produce scatter in toughness values and in growth-rates under fatigue loading, where both cyclic and monotonic failure modes are significant.

Fatigue and Fracture of Nickel Aluminide Composites

1994 ◽  
Vol 350 ◽  
Author(s):  
Padu Ramasundaram ◽  
Randy Bowman ◽  
Wole Soboyejo
Keyword(s):  
Nickel Aluminide ◽  
Room Temperature ◽  
Fracture Mechanisms ◽  
Second Phase ◽  
Reinforced Composites ◽  
Ductile Phase ◽  
Composite Systems ◽  
Heat Treated ◽  
Second Phase Particles ◽  
Fatigue And Fracture

AbstractThe results of preliminary investigations of the room-temperature fatigue and fracture mechanisms in model NiAl composites are presented. The composite systems studied include: NiAl reinforced with ductile second phase particles (Mo); ductile fibers (Mo); brittle second phase particles (zirconia partially stabilized with yttria) and brittle fibers+particles (Al2O3 + zirconia). Mechanisms of fatigue crack growth in heat treated specimens of the fiber-reinforced composites are also elucidated. The investigations indicate that both ductile and brittle reinforcements can enhance the toughness of NiAl significantly, and the ductile phase particulate reinforcement may even contribute to room-temperature ductility in the composite.

Study on the Preparation and Micro Structure of the Mg Containing Porous HA with Ultra-Fine Grain

2009 ◽  
Vol 610-613 ◽  
pp. 1132-1136
Author(s):  
Xing Yi Li ◽  
Xiang Cai Meng ◽  
Guo Quan Liu ◽  
Shi Dan Yuan
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Chemical Precipitation ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Micro Structure ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron ◽  
Second Phase Particles

The Nano-HA powder were synthesized by chemical precipitation with Ca(H2PO4)2•H2O and Ca (OH)2 and porous HA was prepared by sintering with magnesium as pore-creator. Nano-HA powder and porous HA were characterized by wide angle X-ray diffraction, transmission electron microscopy(TEM), scanning electron microscopy (SEM), SEM in combination with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy. The experimental results show that HA powder synthesized by chemical precipitation is nanometer powder. Magnesium was ideal pore-creator for preparation of porous materials. The grain size of porous HA was sub-micron and MgO which existed in the grain boundary of HA as a second phase particles that played the roles of inhibiting the HA grain growth.

Analytical Microscopic Analysis of Precipitates in Hastelloy Alloy C-276

1981 ◽  
Vol 39 ◽  
pp. 280-281
Author(s):  
M. Raghavan ◽  
B. J. Berkowitz ◽  
J. C. Scanlon
Keyword(s):  
Microscopic Analysis ◽  
Scanning Transmission Electron Microscope ◽  
Second Phase ◽  
Precipitation Reaction ◽  
X Ray Diffraction ◽  
Corrosion Properties ◽  
X Ray ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Scanning Transmission

The present investigation was conducted to characterize the second phase particles in Hastelloy C-276 using an analytical Scanning Transmission Electron Microscope in order to understand their effect on the mechanical and Stress Corrosion properties of the alloy. Investigation in our 1aboratoryO) and previous published reports(2-4) have identified two types of precipitation reactions in this alloy. At temperatures in the range of 300-650°C, the alloy precipitates an ordered phase of the type Ni2(Cr, Mo)(1,2). This precipitation reaction is homogeneous with no preferential precipitation at the grain boundaries or twin boundaries. At temperatures above 650°C, several precipitate phases were observed to nucleate heterogeneously at boundaries and using X-ray diffraction techniques, the precipitates were previously identified as the μ, M6C and P phases(3-4). The present investigation was carried out to determine the composition of these second phase particles and this article describes the characterization of these precipitates using X-ray microanalysis and microdiffraction techniques.

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