transgranular fracture
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2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jiankun Xiong ◽  
Jianping Yang ◽  
Haiyan Zhao ◽  
Lin Yang ◽  
Yang Guo ◽  
...  

Creep rupture behavior of dissimilar weldments between FB2 and 30Cr1Mo1V heat-resistant steel by multipass welding at 783 K (510°C) under different stresses (260 to 420 MPa) was researched. The fitted creep rupture exponent is 14.53, and the 10,000 h extrapolating strength values predicted by the power law and Larson-Miller parameter show good agreement with experimental data. The samples exhibit a ductile fracture character and fracture in the weld fusion zone, which has a highly heterogeneous microstructure and grains with different morphologies and sizes and an obvious softening. There exist a decrease in the dislocation and precipitate density and an increase in the subgrain size in the weld metal after creep. The rupture is a transgranular fracture characterized by dimples as a result of microvoid coalescence. Laves phases along with copper-rich precipitates are observed in the vicinity of fracture surface, which creates a stress concentration that can cause transgranular fracture initiation.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7145
Author(s):  
Yuanke Fu ◽  
Liping Wang ◽  
Sicong Zhao ◽  
Yicheng Feng ◽  
Lei Wang

In the present paper, the Mg-11Gd-2Y-1Zn alloys with different Al addition were fabricated by the gravity permanent mold method. The effect of Al content on microstructure evolution and mechanical properties of as-cast Mg-11Gd-2Y-1Zn alloy was studied by metallographic microscope, scanning electron microscope, XRD and tensile testing. The experimental results showed that the microstructure of as-cast Mg-11Gd-2Y-1Zn alloy consisted of α-Mg phase and island-shaped Mg3 (RE, Zn) phase. When Al element was added, Al2RE phase and lamellar Mg12REZn (LPSO) phase were formed in the Mg-11Gd-2Y-1Zn alloy. With increasing Al content, LPSO phase and Mg3 (RE, Zn) phase gradually decreased, while Al2RE phase gradually increased. There were only α-Mg and Al2RE phases in the Mg-11Gd-2Y-1Zn-5Al alloy. With the increase of Al content, the grain size decreased firstly and then increased. When the Al content was 1 wt.%, the grain size of the alloy was the minimum value (28.9 μm). The ultimate tensile strength and elongation increased firstly and then decreased with increasing Al addition. And the fracture mode changed from intergranular fracture to transgranular fracture with increasing addition. When Al addition was 1 wt.%, the maximum ultimate tensile strength reached 225.6 MPa, and the elongation was 7.8%. When the content of Al element was 3 wt.%, the maximum elongation reached 10.2% and the ultimate tensile strength was 207.7 MPa.


Author(s):  
Chawon Hwang ◽  
Jun Du ◽  
Qirong Yang ◽  
Azmi M. Celik ◽  
Kent Christian ◽  
...  

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6570
Author(s):  
Mengjuan Yang ◽  
Chaonan Niu ◽  
Shengpeng Hu ◽  
Xiaoguo Song ◽  
Yinyin Pei ◽  
...  

The brazing of Titanium alloy to Aluminum alloy is of great significance for lightweight application, but the stable surface oxide film limits it. In our work, the surface oxide film was removed by the ion bombardment, the deposited Cu layer by magnetron sputtering was selected as an interlayer, and then the contact reactive brazing of TC4 alloy to Al7075 alloy was realized. The microstructure and joining properties of TC4/Al7075 joints obtained under different parameters were observed and tested, respectively. The results revealed that the intermetallic compounds in the brazing seam reduced with the increased brazing parameters, while the reaction layer adjacent to TC4 alloy continuously thickened. The shear strength improved first and then decreased with the changing of brazing parameters, and the maximum shear strength of ~201.45 ± 4.40 MPa was obtained at 600 °C for 30 min. The fracture path of TC4/Al7075 joints changed from brittle fracture to transgranular fracture, and the intergranular fracture occurred when the brazing temperature was higher than 600 °C and the holding time exceeded 30 min. Our work provides theoretical and technological analyses for brazing TC4/Al7075 and shows potential applications for large-area brazing of titanium/aluminum.


Author(s):  
Unai De Francisco ◽  
Felix Beckmann ◽  
Julian Moosmann ◽  
Nicolas O. Larrosa ◽  
Matthew J. Peel

AbstractIn this investigation, synchrotron X-ray microtomography was used to perform 3D in situ observations of crack initiation and growth during hydrogen environmentally assisted cracking (HEAC) in tensile samples of AA7449-T7651. Two smooth tensile samples with a 1 mm diameter gauge section were held at a fixed displacement ($$\approx 30$$ ≈ 30 % of yield stress) in warm, moist air ($$\approx 76\,^\circ $$ ≈ 76 ∘ C, 73% relative humidity). The samples were then imaged repeatedly using X-ray tomography until they fractured completely. The tomograms showing the nucleation and evolution of intergranular cracks were correlated with electron microscopy fractographs. This enabled the identification of crack initiation sites and the characterisation of the crack growth behaviour relative to the microstructure. The samples were found to fracture within an environmental exposure time of 240 min. Some cracks in both samples nucleated within an exposure time of 80 min (33–40% of the total lifetime). Many cracks were found to nucleate both internally and at the sample surface. However, only superficial cracks contributed to the final fracture surface as they grew faster owing to the direct environmental exposure and the larger crack opening. HEAC occurred prominently via brittle intergranular cracking, and cracks were found to slow down when approaching grain boundary triple junctions. Additionally, crack shielding from nearby cracks and the presence of coarse Al–Cu–Fe particles at the grain boundaries were also found to temporarily reduce the crack growth rates. After prolonged crack growth, the HEAC cracks displayed ductile striations and transgranular fracture, revealing a change in the crack growth mechanism at higher stress intensity factors.


2021 ◽  
Vol 99 (3) ◽  
pp. 40-48
Author(s):  
Y.G. Aftandiliants ◽  

The results of the study of the influence of nickel and molybdenum on the structure and chemical composition of the fracture surface of cast iron with spherical graphite are presented in the paper. It is shown that the fracture of cast iron with spherical graphite occurs along the boundaries of the distribution of graphite balls with matrix, and the fracture of the matrix occurs both by the mechanism of intergranular and transgranular fractures. Molybdenum and nickel alloying changes the mechanism of transgranular fracture of the matrix from brittle for ordinary cast iron to viscous for molybdenum and nickel alloying. It is established that the fracture surfaces of cast iron, depending on the analysis places there are elements such as O, C, P, N, Cu, Ni, Si, Mg. Studies of the distribution of impurities in the near-surface layers of the destroyed samples have shown that the quantity of elements such as oxygen, phosphorus and nitrogen decreases with increasing distance from the fracture surface. The phosphorus quantity is reduced by 40 - 45% in the places of the cast iron matrix, where the graphite balls were located during the alloying of cast iron by molybdenum and nickel. Keywords: cast iron, nickel, molybdenum, alloying, Auger spectroscopy, chemical composition, structure, fracture, surface.


Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1465
Author(s):  
Xianjun Lei ◽  
Xiaopeng Wang ◽  
Fantao Kong ◽  
Haitao Zhou ◽  
Yuyong Chen

Self-induced internal corrosion stress transgranular cracking is investigated theoretically and experimentally linking grain boundary wetting (GBW) and grain boundary diffusion (GBD) to improve the ability to reveal the micro mechanism of crack in compositional gradient-structural intermetallic materials. Theoretical analysis shows that the grain boundary wetting and diffusion induce the diffusion-coupled dynamic internal stresses, and their interaction leads to crack nucleation. The experimental results show a stress concentration zone have been established at the grain boundary interface where the cracks preferentially nucleate and then extend through the inside of the grain to both sides, forming a typical transgranular fracture.


2021 ◽  
Author(s):  
Peiliang Guo ◽  
H.G. Han

Abstract The effect of heat treatment (as-weld, 615℃/48h) on fracture behavior in ENiCrFe-7 weld overlay cladding material was investigated. There were more NbC precipitates in the interdendrites for the heat treatment one after 615℃/48h than that of as-weld, which resulted in the lattice distortion in the interdendrites reduced by the heat treatment. As a result, the fractography was classified as brittle and transgranular fracture and the interdendrites played a major role in the failure of as-weld Alloy ENiCrFe-7, and the fractography was ductility fracture for the heat treatment one after 615℃/48h.`


2021 ◽  
Vol 63 (8) ◽  
pp. 699-704
Author(s):  
Kittipat Suwanpatcharakul ◽  
Nithi Saenarjhan ◽  
Nathi Nakthong ◽  
Anchaleeporn Waritswat Lothongkum ◽  
Gobboon Lothongkum

Abstract AISI 410 martensitic stainless-steel specimens were austenitized at 1253 K then oil quenched and tempered at 573, 673, 773 and 923 K for 3600 s. The impact energy of the specimens was tested at 298, 253, 223, 213 K and measured using ASTM E23 standard. After austenitizing and tempering, the microstructure of the specimens showed carbide precipitation. Tempering at 773 K resulted in the highest hardness due to secondary hardening, while tempering at 923 K resulted in the lowest hardness due to brittle carbide precipitation at the grain boundary which caused softening of the matrix by decreasing the solute carbon content. By contrast, the change in impact energy is inversely proportional to the hardness values. The impact surface of specimens tempered at 573, 673 and 773 K revealed transgranular fracture; on the other hand, the impact surface of the specimen tempered at 923 K revealed intergranular fracture. From our experimental results, the appropriate hardening and tempering procedure of AISI 410 for low temperatures applications is selectable.


Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 637
Author(s):  
Hao Cui ◽  
Zhaoqiang Chen ◽  
Guangchun Xiao ◽  
Lianggang Ji ◽  
Mingdong Yi ◽  
...  

In order to develop a new ceramic tool material with self-repairing capability, Al2O3/TiC/TiB2 ceramic tool material was prepared by vacuum hot-pressure sintering method. The toughening and strengthening mechanism of TiB2 on Al2O3/TiC substrate was analyzed. The results show that the ceramic tool material has good comprehensive mechanical properties when the TiB2 content is 10 vol.%. Its flexural strength was 701.32 MPa, hardness was 18.3 GPa, and fracture toughness was 6.2 MPa·m1/2, which were improved by 11.6%, 2.2% and 16.1% respectively, compared with the Al2O3/TiC tool material. Fracture surfaces of the Al2O3/TiC/TiB2 ceramic tool material were characterized by SEM, EDS and XRD. The results showed that the fracture mode was a mixture of transgranular fracture and intergranular fracture. The growth of Al2O3 and TiC grains can be effectively inhibited by adding appropriate amount of TiB2, and the internal grains of the material can be refined. The TiB2 has a uniform distribution in the matrix and acts as a diffusion toughening agent. The cutting performance of Al2O3/TiC/10 vol.%TiB2 tool material was further investigated. Experiments conducted on tools made of Al2O3/TiC and Al2O3/TiC/TiB2 materials showed that the main forms of wear for both tools were abrasive wear and bonded wear. The friction coefficient of Al2O3/TiC/TiB2 tools was reduced by 10.77% compared to Al2O3/TiC tools.


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