ON CRACK PROPAGATION ALONG CRYSTALLOGRAPHIC SLIP BANDS

1981 ◽  
pp. 18-22 ◽  
Author(s):  
D.A. Koss ◽  
K.S. Chan
Keyword(s):  
Crack Propagation ◽  
Slip Bands ◽  
Crystallographic Slip

On the Micromechanisms of Fatigue Crack Propagation in Aluminum Cast Alloys

2013 ◽  
Vol 592-593 ◽  
pp. 393-396 ◽  
Author(s):  
Ulrich Krupp ◽  
Alexander Giertler ◽  
Stefanie Siegfanz ◽  
Wilhelm Michels
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Eutectic Silicon ◽  
Control Mode ◽  
Polished Surface ◽  
Strengthening Effect ◽  
Long Distance ◽  
Heat Treated ◽  
Crystallographic Slip

Specimens of the common cast alloy Al-7Si-0.3Mg (A356) were solution heat treated at different temperatures and times to modify (i) the precipitation strengthening effect in the aluminum solid solution phase and (ii) to spheroidize the eutectic silicon. Just 15 minutes of solution heat treatment at a temperature of 540°C are sufficient to reach the desired effect. Cyclic loading experiments revealed an increase in fatigue life as compared to specimens heat treated at lower temperatures. In particular in the HCF regime, fatigue cracks that were originally initiated at pores follow crystallographic slip bands under shear control (mode II) as it was proven by automated EBSD (electron back scatter diffraction) measurements. The smoothly polished surface of the fatigue specimens was observed continuously by a long-distance microscope and discontinuously by SEM (scanning electron microscopy) to identify the fatigue crack propagation mechanisms. It was shown that da/dN decreases strongly when the crack tip interacts with the eutectic areas. Obviously, the blocking effect of the eutectic silicon particles makes the crack leaving the straight slip-band path.

Modeling lattice rotation fields from discrete crystallographic slip bands in superalloys

2021 ◽  
Vol 49 ◽  
pp. 101468
Author(s):  
Marat I. Latypov ◽  
Jonathan M. Hestroffer ◽  
Jean-Charles Stinville ◽  
Jason R. Mayeur ◽  
Tresa M. Pollock ◽  
...  
Keyword(s):  
Lattice Rotation ◽  
Slip Bands ◽  
Crystallographic Slip

scholarly journals Influence of Carbide Morphology on the Deformation and Fracture Mechanisms of Spheroidized 14CrMoR Steel

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1221 ◽  
Author(s):  
Shifu Wang ◽  
Luowei Cao ◽  
Zheng Zhang
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Steel Sample ◽  
Fracture Mechanisms ◽  
Propagation Behavior ◽  
Slip Bands ◽  
Carbide Morphology ◽  
Deformation And Fracture ◽  
Crack Propagation Behavior

The influence of carbide morphology on the deformation and fracture mechanisms of as-received and complete spheroidization 14Cr1MoR steel was investigated using an in situ scanning electron microscope (SEM) under tension testing. During spheroidization damage, the carbide morphology changed from the original lamellar cementite present in pearlite to granular M23C6 carbide, which was concentrated along the ferrite grain boundaries. The yield strength and tensile strength of 14Cr1MoR steel decreased with the increasing degree of spheroidization damage. In situ SEM observations revealed that the deformation and crack initiation started from the ferrite matrix in both as-received and completely spheroidization-damaged 14Cr1MoR steel samples. However, the extension of slip bands and crack propagation behavior of both samples were different during the in situ tensile process, which could be ascribed to the difference in carbide morphology. In the as-received 14Cr1MoR steel sample, hard and brittle lamellar pearlite resulted in high-strength ferrite/ pearlite boundaries, which inhibited the movement of slip bands. With further deformation, the concentration of stress at the crack tip resulted in the emergence and propagation of cracks along the ferrite/pearlite boundaries. In the case of the completely spheroidized 14Cr1MoR steel sample, slip bands bypassed the grain boundary carbide and continuously expanded into the neighboring ferrite grain. In addition, micro-voids and fractures of grain boundary carbides were observed due to the large stress concentration at the front of crack tip. Then, the micro-voids connected with the main crack to complete the crack propagation behavior. The morphological changes of carbides deteriorated the mechanical properties and altered the fracture behavior of 14Cr1MoR steel. It is worth noting that the fracture surface morphology of 14Cr1MoR steel changed from a combination of lamellar fracture and dimpled morphology to a completely dimples-dominated morphology after spheroidization.

Deviations of Microcrack during Propagation in Thin Films of Austenitic Steel and Accompanying Accommodative Processes

2014 ◽  
Vol 627 ◽  
pp. 297-300 ◽  
Author(s):  
Tamaz Eterashvili ◽  
T. Dzigrashvili ◽  
M. Vardosanidze
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Crack Propagation ◽  
Low Cycle Fatigue ◽  
Polycrystalline Sample ◽  
Crystallographic Analysis ◽  
Cycle Fatigue ◽  
Initial Direction ◽  
Slip Bands ◽  
Transmission Electron

The work deals with the transmission electron microscopy (TEM) study of thin films of chromium-nickel Х18Н10 steel. The films were prepared from bulk samples after low cycle fatigue (LCF) tests. Focus was made on the processes accompanying propagation of small microcracks. Particularly, the microstructure changes near the crack tip were analyzed in terms of accommodation processes taking place during crack propagation, such as formation of slip bands, twins etc. The authors conducted crystallographic analysis of the defects formed during crack propagation in correlation with the reasons of their initiation and homogenous length of the slip bands. Thus, the reasons of microcrack deviation from the initial direction were determined. The research has shown that the most convenient microstructure variables in the austenitic crystals of polycrystalline sample, affecting the microcrack deviation, are microstructure, crystallography and the homogenous length of slip bands.

Effect of Microscopic Structure on High-Cycle Fatigue Behavior in Nano-Components

2014 ◽  
Vol 891-892 ◽  
pp. 1705-1710
Author(s):  
Takashi Sumigawa ◽  
Kenta Matsumoto ◽  
Takayuki Kitamura
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fem Analysis ◽  
Amorphous Layer ◽  
Microscopic Structure ◽  
Cycle Fatigue ◽  
Si Substrate ◽  
Slip Bands ◽  
Crystallographic Slip ◽  
Schmid Factor

In order to investigate the effect of microscopic structure on fatigue behavior of nanoscale components, a resonant fatigue experiment is conducted using a nanocomponents specimen where the test section is composed of a single crystalline Si substrate, a 200 nm thickness Cu polycrystalline film and a SiN amorphous layer. In the specimen, only the Cu portion plastically deforms because the yield stress is lower than those of other materials. The shape and the crystalline orientation of each grain on the surface of Cu portion are specified by means of EBSD. Although crystallographic slip bands with a width of a few tens of nanometers appear only in a grain of Cu portion, the grain is different from that expected by the Schmid factor. A FEM analysis, which takes into account the deformation anisotropy of grains, reveals that shear stress to generate slip bands is concentrated on the grain owing to the deformation constraint by neighboring crystals and components.

Formation of Persistent Slip Band in Fatigued Copper Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 470-471
Author(s):  
N. Y. Jin
Keyword(s):  
Volume Fraction ◽  
Fatigue Cracks ◽  
Wall Structure ◽  
Matrix Structure ◽  
Dislocation Dipole ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
The Matrix ◽  
Hard Shell ◽  
Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

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