A Large Plastic Elongation followed by Brittle Fracture : a Case of Tensile Deformation at –180 °C in a DP Steel

Uni-axial tensile test was conducted at room temperature on a weak texture AZ31B magnesium alloy at different strain rate, from 2.8×10-5s-1 to 1.1×10-1s-1. The mechanical behavior was investigated. It was found that as strain rate is increased, flat character of the stress-strain curves can be found and {10-12} tension twinning is responsible for this phenomenon. The sample exhibites a brittle fracture at 1.1×10-1s-1 strain rate while exhibites a ductile fracture character at 2.8×10-5s-1 strain rate.

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The Fracture Behavior of Hydrogen-Charged A508III Low Alloy Steel in the Process of Natural Hydrogen-Escaping

Volume 2: Plant Systems, Structures, Components and Materials ◽

10.1115/icone25-67246 ◽

2017 ◽

Author(s):

Qian Xiao ◽

Zhanpeng Lu ◽

Junjie Chen ◽

Hao Peng

Keyword(s):

Brittle Fracture ◽

Fracture Mode ◽

Fracture Behavior ◽

Defect Formation ◽

Tensile Deformation ◽

Decisive Role ◽

Surface Characteristics ◽

Void Coalescence ◽

Brittle Ductile Transition ◽

Time Required

The effects of hydrogen charging as well as natural hydrogen escaping on fracture behavior of A508III steel at room temperature were investigated. The presence of hydrogen caused a slightly increase in yield strength and a distinct decrease in the elongation and reduction in area, but no or hardly any influence on the ultimate tensile strength (UTS). Non-charged specimen exhibited a ductile mode of failure with micro-void coalescence, while the H-charged specimens showed typical brittle fracture with “fish eye” appearance. The presence of hydrogen gave an increase in the dislocation density after tensile deformation. Nucleation of defects occurred primarily from the inclusions which contain complex oxides of Al, Mg and Ca, and (Ca, Mn)S, as well as MnS only to a small extent. The parameters of non-metallic inclusions, such as type, shape, size and content play the decisive role at the defect formation. In the process of natural H-escaping, the fracture surface characteristics of H-charged steels gradually transferred from brittle fracture mode to ductile fracture mode. At the same H-charged time, the H-escaping time required for the brittle-ductile transition was related to the H-charged current density.

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Microstructure and Tensile Deformation Behavior of a Hot-Rolled Directly Quenched and Dynamically Partitioned Steel Containing Proeutectoid Ferrite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.246 ◽

2015 ◽

Vol 817 ◽

pp. 246-251 ◽

Cited By ~ 1

Author(s):

Xiao Dong Tan ◽

Yun Bo Xu ◽

Xiao Long Yang ◽

Zhi Ping Hu ◽

Fei Peng ◽

...

Keyword(s):

Tensile Deformation ◽

Control Process ◽

Low Carbon Steel ◽

Yield Ratio ◽

Uniaxial Tensile ◽

Uniaxial Tensile Test ◽

Low Carbon ◽

Dp Steel ◽

Proeutectoid Ferrite ◽

Deformation Behaviors

Hot-rolling direct quenching and dynamical partitioning (HDQ&DP) processes were applied to a low-carbon steel containing silicon and manganese based on thermo-mechanical control process (TMCP) technology and ultra-fast cooling (UFC) technology. The microstructures and phase compositions were characterized and analyzed using SEM, EBSD, TEM and XRD. The mechanical properties and tensile deformation behaviors were investigated by means of uniaxial tensile test. The microstructures and tensile deformation behaviors of both HDQ&DP steel with and without proeutectoid ferrite were comprehensively expounded by comparing with each other. Results show that the amount of retained austenite in the HDQ&DP steel with proeutectoid ferrite can reach up to 17.3%, which is higher than that in the HDQ&DP steel without proeutectoid ferrite (15.7%). The HDQ&DP steel without proeutectoid ferrite possesses extremely high ultimate tensile strength (UTS) up to 1700 MPa with yield ratio about 0.73 and elongation about 11.5%. The introduction of proeutectoid ferrite can result in a moderate decrease of UTS to 1240-1400 MPa, a drastic decrease of yield ratio to 0.51-0.69 and a certain increase of elongation to 13.0-13.7%. The existence of the proeutectoid ferrite can partly enhance the work hardening ability of the steel and may improve its formability. It is concluded that the HDQ&DP steel with relatively large amount of proeutectoid ferrite and certain amount of bainite has extensive application prospects.

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Application of WES2808 to Brittle Fracture Assessment for High Strength Gas Pipelines

Volume 3: Pipeline and Riser Technology; CFD and VIV ◽

10.1115/omae2007-29246 ◽

2007 ◽

Cited By ~ 4

Author(s):

Takahiro Kubo ◽

Satoshi Igi ◽

Tsunehisa Handa ◽

Nobuhisa Suzuki ◽

Masao Toyoda ◽

...

Keyword(s):

Fracture Toughness ◽

Brittle Fracture ◽

Large Scale ◽

Biaxial Loading ◽

Tensile Deformation ◽

High Strength ◽

Assessment Method ◽

Gas Pipelines ◽

Charpy Test ◽

Assessing Method

This paper presents the results of a preliminary study to establish an assessing method for the tensile strain limit against brittle fracture of pressurized gas pipelines subjected to axial tensile deformation. The basis of the assessment method is the Japan Welding Engineering Society standard WES2808–2003. WES2808 provides a procedure for evaluating the fracture limit using the CTOD design curve relating flaw size, applied strain and fracture mechanical parameter (CTOD). The main characteristics of the method are a consideration of the deterioration of the fracture toughness of material resulting from large cyclic and dynamic straining, a correction of CTOD fracture toughness for constraint loss in structural components in large scale yielding, and an estimation of critical CTOD value from Charpy test results. Modifications of the procedure to enable evaluation of the fracture properties of high strength gas pipelines under biaxial loading conditions are studied.

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TEM examination of 2014-SiC metal matrix composite

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105692 ◽

1988 ◽

Vol 46 ◽

pp. 726-727

Author(s):

M. G. Burke ◽

M. N. Gungor ◽

P. K. Liaw

Keyword(s):

Metal Matrix Composite ◽

Metal Matrix Composites ◽

Matrix Composite ◽

Metal Matrix ◽

Tensile Deformation ◽

Microstructural Characterization ◽

Thin Foil ◽

Matrix Alloy ◽

Matrix Composites ◽

Ion Milling

Aluminum-based metal matrix composites offer unique combinations of high specific strength and high stiffness. The improvement in strength and stiffness is related to the particulate reinforcement and the particular matrix alloy chosen. In this way, the metal matrix composite can be tailored for specific materials applications. The microstructural characterization of metal matrix composites is thus important in the development of these materials. In this study, the structure of a p/m 2014-SiC particulate metal matrix composite has been examined after extrusion and tensile deformation.Thin-foil specimens of the 2014-20 vol.% SiCp metal matrix composite were prepared by dimpling to approximately 35 μm prior to ion-milling using a Gatan Dual Ion Mill equipped with a cold stage. These samples were then examined in a Philips 400T TEM/STEM operated at 120 kV. Two material conditions were evaluated: after extrusion (80:1); and after tensile deformation at 250°C.

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