Criteria for Crack Extension and Arrest in Residual, Localized Stress Fields Associated with Second Phase Particles

1974 ◽  
pp. 599-609 ◽  
Author(s):  
F. F. Lange
Keyword(s):  
Crack Extension ◽  
Stress Fields ◽  
Second Phase ◽  
Second Phase Particles

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.

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.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

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.

Development of Second-Phase Particles during Solidification and Homogenization of Aluminium Alloy AlMn1

2019 ◽  
Vol 56 (5) ◽  
pp. 317-341 ◽  
Author(s):  
O. Engler ◽  
K. Kuhnke ◽  
K. Westphal
Keyword(s):  
Aluminium Alloy ◽  
Second Phase ◽  
Second Phase Particles

scholarly journals Evidence of hydrogen trapping at second phase particles in zirconium alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Jones ◽  
Vidur Tuli ◽  
Zaheen Shah ◽  
Mhairi Gass ◽  
Patrick A. Burr ◽  
...  
Keyword(s):  
Density Functional ◽  
Secondary Ion Mass Spectrometry ◽  
Zirconium Alloys ◽  
Nuclear Industry ◽  
Second Phase ◽  
Hydrogen Trapping ◽  
Functional Theory ◽  
Second Phase Particles ◽  
Hydrogen Isotope Ratios ◽  
Dft Modelling

AbstractZirconium alloys are used in safety–critical roles in the nuclear industry and their degradation due to ingress of hydrogen in service is a concern. In this work experimental evidence, supported by density functional theory modelling, shows that the α-Zr matrix surrounding second phase particles acts as a trapping site for hydrogen, which has not been previously reported in zirconium. This is unaccounted for in current models of hydrogen behaviour in Zr alloys and as such could impact development of these models. Zircaloy-2 and Zircaloy-4 samples were corroded at 350 °C in simulated pressurised water reactor coolant before being isotopically spiked with 2H2O in a second autoclave step. The distribution of 2H, Fe and Cr was characterised using nanoscale secondary ion mass spectrometry (NanoSIMS) and high-resolution energy dispersive X-ray spectroscopy. 2H− was found to be concentrated around second phase particles in the α-Zr lattice with peak hydrogen isotope ratios of 2H/1H = 0.018–0.082. DFT modelling confirms that the hydrogen thermodynamically favours sitting in the surrounding zirconium matrix rather than within the second phase particles. Knowledge of this trapping mechanism will inform the development of current understanding of zirconium alloy degradation through-life.

scholarly journals On the variety and formation sequence of second-phase particles in nickel-based superalloys fabricated by laser powder bed fusion

Materialia ◽  
2021 ◽  
Vol 15 ◽  
pp. 101037
Author(s):  
A. Després ◽  
C. Mayer ◽  
M. Veron ◽  
E.F. Rauch ◽  
M. Bugnet ◽  
...  
Keyword(s):  
Second Phase ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Second Phase Particles

Structural Changes in a 9%Cr Creep Resistant Steel during Creep Test

2012 ◽  
Vol 715-716 ◽  
pp. 895-900
Author(s):  
Valeriy Dudko ◽  
Andrey Belyakov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
Rustam Kaibyshev
Keyword(s):  
Structural Changes ◽  
Subgrain Size ◽  
Large Strain ◽  
Particle Growth ◽  
Second Phase ◽  
Second Phase Particles ◽  
Creep Rupture Test ◽  
Lath Structure ◽  
Creep Regime ◽  
Effective Stabilization

Structural changes in a 9%Cr martensitic steel after 1%, 4% creep and creep rupture test at 650°C and stress of 118 MPa were examined. Heat treatment provided the formation of tempered martensite lath structure (TMLS) in the steel. The precipitations of second phase particles along block and lath boundaries provide effective stabilization of the TMSL under annealing/aging condition. This structure hardly changed under creep conditions in grip portion of crept sample. Significant coarsening of both the second phase particles and the martensite laths takes place in neck portion. In addition, the latter ones lose their original morphology and are replaced by large strain-induced subgrains. It should be noted that the increase of subgrain size is in almost direct proportion to the particle growth during the creep to 4% strain. The rapid growth of martesite laths followed by their evolution to deformation subgrains takes place within the tertiary creep regime.

Monte Carlo study on abnormal growth of Goss grains in Fe-3%Si steel induced by second-phase particles

2016 ◽  
Vol 23 (12) ◽  
pp. 1397-1403 ◽  
Author(s):  
Dong-qun Xin ◽  
Cheng-xu He ◽  
Xue-hai Gong ◽  
Hao Wang ◽  
Li Meng ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study ◽  
Second Phase ◽  
Abnormal Growth ◽  
Second Phase Particles

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

2012 ◽  
Vol 715-716 ◽  
pp. 346-353
Author(s):  
H. Paul ◽  
T. Baudin ◽  
K. Kudłacz ◽  
A. Morawiec
Keyword(s):  
High Pressure Torsion ◽  
Deformation Mode ◽  
Second Phase ◽  
Orientation Measurement ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
The Matrix ◽  
Electron Microscopes ◽  
Different Strains

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

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