Embrittlement of Steels by Liquid Zinc: Crack Propagation after Grain Boundary Wetting

2014 ◽  
Vol 922 ◽  
pp. 161-166 ◽  
Author(s):  
Renaud Frappier ◽  
Pascal Paillard ◽  
René Le Gall ◽  
Thomas Dupuy
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Tensile Elongation ◽  
Crack Propagation Rate ◽  
High Strength ◽  
Propagation Rate ◽  
Atomic Scale ◽  
Temperature Range ◽  
Grain Boundary Wetting

This study characterizes the mechanical behavior of an advanced multiphase high strength steel by means of high temperature tensile testing. The results show a drastic reduction of the maximum tensile elongation from around 700 °C up to 950°C. Scanning electron microscopy investigations show that the temperature range for embrittlement is correlated with the total wetting of steel grain boundaries. Under external strain, crack propagates along the grain boundaries according to a mechanism that leads to the presence of nanometer-thick films of Zn at the crack tip, as shown by fine X-ray spectroscopy analyses. The effective temperature range for embrittlement is discussed. Mechanisms of i) external stress-free wetting, and ii) atomic-scale crack propagation, are today under discussion in the light of the literature, regarding in particular recent experimental results and theory about grain boundary wetting, intergranular penetration, and the correlation between surface energy and crack propagation rate.

The Fatigue Crack Propagation of Al–Mg–Mn–Zr Alloy with Erbium

2015 ◽  
Vol 1120-1121 ◽  
pp. 1083-1088
Author(s):  
Xin Lei ◽  
Hui Huang ◽  
Huan Wang
Keyword(s):  
Fatigue Crack ◽  
Grain Boundary ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Propagation Path ◽  
Fatigue Crack Propagation Rate ◽  
Second Phase ◽  
Second Phases

This study investigated the fatigue crack propagation of Al–Mg–Mn–Zr alloys with erbium. The research found that in this alloy the crack propagation path prefers to extend along the grain boundary. If there are too many second phases or impurities in the gain boundary, the crack propagation will be influenced. The dispersed Al3(Er, Zr) precipitate in the alloy can act as a core of heterogeneous nucleation to attract Mg, Zn and Al element, and reduce the large brittle Al3Mg2second phase appear on the grain boundary, so the fatigue crack propagation rate can be slow down. In addition, these Al3(Er, Zr) precipitate can pin the dislocation in the alloy to reduce stress concentration at the grain boundary, so it also has some positive effect to the fatigue crack propagation.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

scholarly journals Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4380
Author(s):  
Alirio Andres Bautista Villamil ◽  
Juan Pablo Casas Rodriguez ◽  
Alicia Porras Holguin ◽  
Maribel Silva Barrera
Keyword(s):  
Crack Propagation ◽  
Structural Integrity ◽  
Crack Propagation Rate ◽  
Fatigue Loading ◽  
Propagation Rate ◽  
Operating Conditions ◽  
Impact Testing ◽  
Mode I ◽  
Mode I Crack ◽  
Constant Amplitude

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

scholarly journals Crack Propagation Behavior of a Ni-Based Single-Crystal Superalloy during In Situ SEM Tensile Test at 1000 °C

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1047
Author(s):  
Wenxiang Jiang ◽  
Xiaoyi Ren ◽  
Jinghao Zhao ◽  
Jianli Zhou ◽  
Jinyao Ma ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Tensile Test ◽  
Single Crystal ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Single Crystal Superalloy ◽  
Propagation Path ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy.

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