Effect of Strain Rate on Hydrogen Evolution during Deformation in Al-Zn-Mg Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 295-300
Author(s):  
Keitaro Horikawa ◽  
Hiroyuki Yamada ◽  
Masahide Mutsuo ◽  
Hidetoshi Kobayashi
Keyword(s):  
Strain Rate ◽  
Grain Boundaries ◽  
Testing Machine ◽  
Hydrogen Gas ◽  
Mg Alloys ◽  
Second Phase ◽  
Gas Evolution ◽  
Hydrogen Atoms ◽  
Deformation And Fracture ◽  
The Moment

Hydrogen gas evolution behaviour during deformation and fracture in Al-Zn-Mg alloys with and without copper additions was examined by using a testing machine equipped with a quadrupole mass spectrometer in an ultrahigh vacuum chamber (QMS-UHV) and by a hydrogen microprint technique (HMT). The QMS-UHV testing revealed that hydrogen gas was evolved at the moment of grain boundary fracture, in particular. This suggested that hydrogen atoms primarily dissolved were trapped at the grain boundaries before the fracture. It was also revealed that hydrogen gas evolution behaviour was changed according to the testing strain rate. The HMT also revealed that silver particles, which represented the emission sites of hydrogen, were observed mainly around the second phase inclusions and the grain boundaries.

Cavity of Al-Cu-Mg Alloy during Superplastic Deformation

2007 ◽  
Vol 551-552 ◽  
pp. 645-650
Author(s):  
Min Wang ◽  
Hong Zhen Guo ◽  
Y.J. Liu
Keyword(s):  
Strain Rate ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Room Temperature ◽  
Mg Alloy ◽  
Deformation Condition ◽  
Second Phase ◽  
Rate Condition ◽  
Second Phase Particles ◽  
Strain Rate Condition

According to the characteristic of appearing cavitation in the metals during superplastic deformation, the influence of strain rate on cavity evolvement, the influence of cavity on superplastic deformation capability, and the formation, development process of cavity were investigated for Al-Cu-Mg alloy (i.e. coarse–grained LY12). The results show that: ①The pore nucleation occurs not only at triangle grain boundaries, but also along nearby the second phase particles, and even within grains. The cavities at the triangle grain boundaries are present in V-shape, others near the second phase particles and within grains are present in O-shape. These cavities may result from disharmony slippage of grain boundaries. ②The tendency of cavity development decreases with increasing of strain-rate. In lower strain-rate condition, though Al-Cu-Mg alloy has better superplasticity, many big cavities in the specimen may reduce the room temperature properties of the alloy. In higher strain-rate condition, Al-Cu-Mg alloy has certain superplasticity and room temperature properties as well as few cavities forming. By analyzing, viscous layer on grain boundaries is very thin and grain sizes can be refined during their extruding and rotating each other in higher strain-rate superplastic deformation condition. ③Growth and coalescence of cavity are the main reason of the superplastic fracture of Al-Cu-Mg alloy. And small and a certain amount of cavities with dispersion and independence state are very useful to crystal boundary slippage.

Deformation and fracture of high-entropy AlCoCrFeNi alloy

2021 ◽  
pp. 103-108
Author(s):  
Yu.F. Ivanov ◽  
◽  
V.E. Gromov ◽  
K.A. Osintsev ◽  
S.V. Konovalov ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Tensile Tests ◽  
High Entropy Alloy ◽  
Second Phase ◽  
High Entropy ◽  
Deformation And Fracture ◽  
Distribution Of Elements ◽  
Microscopy Method ◽  
Second Phases ◽  
Wire Arc Additive Manufacturing

Using wire-arc additive manufacturing (WAAM)technology in an atmosphere of argon gas a non - equatomic high entropy alloy (HEA) of AlCoCrFeNi system is obtained: Al (35.67±1.34 at%), Ni (33.79±0.46 at%), Fe (17.28±1.83 at%), Cr (8.28±0.15 at%), Co (4.99±0.09 at%). Scanning electron microscopy method revealed that HEA is a polycrystal material having the grain size (4-15) µm with the particles of second phase located along the grain boundaries. Mapping methods showed that grain volumes are enriched in aluminum and nickel, while grain boundaries contain chromium and iron. Cobalt is distributed in the crystal lattice of the resulting HEA quasi-uniformly. It is shown that during tensile tests, the material was destroyed by the mechanism of intra-grain cleavage. The formation of brittle cracks along the boundaries and at the junctions of grain boundaries, i.e., in places containing inclusions of the second phases, is revealed. It was suggested that one of the reasons for the increased brittleness of HEA, is revealed uneven distribution of elements in the microstructure of the alloy and also the presence in the volume of material discontinuities of various shapes and sizes.

Relationship Between the Ductility and Impurity Hydrogen in Ni3Al

1994 ◽  
Vol 364 ◽  
Author(s):  
R. Chikaizumi ◽  
G. Itoh ◽  
M. Kanno ◽  
H. Okada
Keyword(s):  
High Vacuum ◽  
Tensile Tests ◽  
Hydrogen Gas ◽  
Ultra High Vacuum ◽  
Transgranular Fracture ◽  
Hydrogen Atoms ◽  
Impurity Hydrogen ◽  
The Moment ◽  
Evolution Behavior ◽  
Growth Of Voids

AbstractTensile tests were carried out on B-doped and undoped Ni3Al having different hydrogen contents in order to examine whether the amount of impurity hydrogen affects the ductility of Ni3Al. Specimens were melted either in a high vacuum of ∼10−3Pa or argon, isothermally forged and finally annealed for 15hr at 430°C in an ultra high vacuum of ∼10−3Pa or in argon, respectively. Measurement of hydrogen gas evolved from the specimen during the annealing at 430°C in an ultra high vacuum of ∼10−7Pa confirmed that vacuum treated specimen had actually smaller hydrogen content than the argon treated one. The ductility of vacuum treated specimens both B-doped and undoped was found to be larger than that of argon treated ones, which means a detrimental influence of hydrogen. Hydrogen evolution behavior during the test on B-dopcd specimens in an ultra high vacuum of ∼10−8Pa revealed that the amount of hydrogen gas evolved at the moment of fracture was smaller in vacuum treated specimens than in argon treated one. Impurity hydrogen atoms were considered to move and enhance the formation and growth of voids, accelerating transgranular fracture.

Development of Creep Resistant Mg Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 521-524 ◽  
Author(s):  
Dae H. Kang ◽  
Min S. Yoo ◽  
Sung S. Park ◽  
Nack J. Kim
Keyword(s):  
Grain Boundaries ◽  
Mg Alloys ◽  
Az91 Alloy ◽  
Second Phase ◽  
Creep Properties ◽  
Unstable Particles ◽  
Elevated Temperature Tensile ◽  
Die Cast ◽  
Second Phase Particles ◽  
Stable Particles

A study has been made on the tensile and creep properties of squeeze and die cast Mg alloys, with emphasis on the effect of second phase particles. Two different microstructures were compared; the microstructure with thermally unstable particles along grain boundaries (AZ91 alloy) and the microstructure with thermally stable particles along grain boundaries as well as within matrix (MX alloy). The experimental MX alloy has equivalent room temperature tensile strength to AZ91 alloy with higher ductility. Moreover, elevated temperature tensile properties and creep resistance of MX alloy are higher than those of AZ91 alloy. Such improved properties of MX alloy over those of AZ91 alloy are due to the optimized microstructure of the former.

Hydrogen Evolution Behavior during Tensile Deformation in Austenitic Stainless Steels Exposed to High Compressed Hydrogen Atmospheres

2010 ◽  
Vol 654-656 ◽  
pp. 2519-2522
Author(s):  
Keitaro Horikawa ◽  
Hidetoshi Kobayashi ◽  
Motohiro Kanno
Keyword(s):  
Hydrogen Evolution ◽  
Stainless Steels ◽  
Tensile Deformation ◽  
Testing Machine ◽  
Austenitic Stainless Steels ◽  
Local Deformation ◽  
Hydrogen Gas ◽  
Deformation And Fracture ◽  
Rate Testing ◽  
Evolution Behavior

Hydrogen embrittlement sensitivity of austenitic stainless steels, SUS316L and SUS310S exposed to high compressed hydrogen gas atmospheres was evaluated by means of a slow strain rate testing (SSRT) in air. Hydrogen evolution behavior during tensile deformation and fracture was also investigated by using a testing machine equipped with a quadrupole mass spectrometer installed in an ultrahigh vacuum chamber. When the SUS 316L specimen with hydrogen gas charging were deformed at a very slow crosshead speed of 1.67 nm/s, local deformation was promoted as compared to the specimen without hydrogen gas charging. On the other hand, no decrease of the ductility was observed in the SUS310S specimen with hydrogen gas charging even in the SSRT. In the hydrogen charged SUS316L specimen, the amount of continuous hydrogen evolution throughout deformation was much higher than that in the specimen without hydrogen gas charging. In addition, sudden hydrogen evolutions were sometimes identified in the SUS316L specimen with hydrogen gas charging during the deformation.

Dynamic Observation of Hydrogen Gas Release during Crack Propagation in Al-Zn-Mg Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 168-173
Author(s):  
Keitaro Horikawa ◽  
Shunsuke Hokazono ◽  
Hidetoshi Kobayashi
Keyword(s):  
Grain Boundary ◽  
High Speed ◽  
Notch Root ◽  
Sampling Rate ◽  
Testing Machine ◽  
Initial Crack ◽  
Hydrogen Gas ◽  
Gas Evolution ◽  
Tensile Testing Machine ◽  
Air Atmosphere

We have developed a new testing device, which is capable of detecting hydrogen gas evolution from the microstructural changes at the same timing. The device is composed of the tensile testing machine equipped with a high-speed microscope and two types of quadrupole mass spectrometers installed in the ultrahigh vacuum chamber. Sampling rate of microscopic observation is 2000 fps. Hydrogen or deuterium was pre-charged to the 7075 aluminum alloy by means of the slow strain rate deformation, together with the exposure under the humid air atmosphere. The hydrogen amount was measured by using a thermal desorption analysis in advance. As a result, it was revealed that hydrogen gas was evolved when the surface crack was generated around the notch root of the test specimen. SEM observation also showed that the initial crack is related to the propagation of grain boundary fracture around the notch root. When compared to the microstructure and the hydrogen gas evolution near the notch root, the hydrogen amount evolved at the grain boundary was estimated to be about 3.0×10-7mol/m2.

scholarly journals FABRICATION OF CAST ALUMINIUM-SILICON (Al-Si) AND ALUMINIUM-MAGNESIUM (Al-Mg) ALLOYS AND THEIR PROPERTIES

2016 ◽  
Vol 22 (4) ◽  
pp. 212
Author(s):  
Harish Sharma Akkera ◽  
N. Nanda Kumar Reddy ◽  
Madhukar Poloju ◽  
M. Chandra Sekhar ◽  
C. Yuvaraj ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Testing Machine ◽  
Mg Alloys ◽  
Homogeneous Distribution ◽  
Second Phase ◽  
Wear Properties ◽  
Hardness Tester ◽  
Universal Testing ◽  
Hardness Values ◽  
Al Mg Alloys

<p>In the present investigation, three different aluminium-silicon (Al-Si) containing 7 wt.%, 12 wt.%, 14 wt.% of silicon and two different aluminium-magnesium (Al-Mg) alloys containing 2.5 wt.%, 4.5 wt.% of magnesium were prepared by casting route method. The prepared Al-Si and Al-Mg alloys have homogeneous distribution of the second phase throughout the cast. The microstructural analyses were done by using both optical and scanning electron microscope. Hardness values were measured in a Vickers hardness tester and tensile properties were determined by using Instron universal testing machine. Further, the wear properties were determined by using a ball-on-plate wear tester. The results highlight that the hardness, tensile properties and wear resistance increases with increasing percentage of second phase in aluminium. The worn surfaces of these alloys revealed that the surfaces shows cracks, grooves, scoring marks and debris.</p>

Effect of Cr on Grain Refinement and Mechanical Properties of Al-Si-Mg Alloys

2015 ◽  
Vol 789-790 ◽  
pp. 95-99 ◽  
Author(s):  
Aakash Kumar ◽  
Gaurav Sharma ◽  
Chandrabalan Sasikumar ◽  
Shahrukh Shamim ◽  
Himkar Singh
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Growth ◽  
Testing Machine ◽  
Weight Percent ◽  
Stir Casting ◽  
Optical Microscope ◽  
Mg Alloys ◽  
Grain Structure ◽  
Second Phase

Grain growth of Aluminium alloys at high temperature reduces their strength significantly. Therefore it is essential to control the grain growth by suitable techniques. The effect of Cr on refining the grain structure of Al alloys is investigated in the present work. Cr is added into Al-Si-Mg alloy by stir casting techniques. Subsequently the alloys were subjected to annealing at 500oC for 1 hour to study the grain growth behavior of these alloys. An optical microscope is used to analyze the grain size and microstructure. The mechanical properties of these alloys were studied using a universal testing machine. The Cr additions were varied between 0.5 to 4 weight percent. The Cr addition had shown a significant effect in refining the grain size of Al-Si-Mg alloys. The average grain diameter after annealing was found to be about 151 μm in unalloyed samples while, the 2 wt % Cr added samples showed about 92 μm. The second phase particles, Al7Cr found precipitated along the grain boundaries apart from Al2Si and Mg2Si. However Cr additions more than 2% does not show significant role in refining the grain size. Cr also improved the mechanical properties such as yield strength, ultimate tensile strength and fracture toughness moderately.

Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions

2012 ◽  
Vol 534 ◽  
pp. 495-503 ◽  
Author(s):  
Keitaro Horikawa ◽  
Nobuaki Ando ◽  
Hidetoshi Kobayashi ◽  
Wataru Urushihara
Keyword(s):  
Hydrogen Gas ◽  
Gas Evolution ◽  
Deformation And Fracture
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