scholarly journals The Influence of Different Microstructure on Tensile Deformation and Acoustic Emission Behaviors of Low-Alloy Steel

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4981
Author(s):  
Wenbin Ma ◽  
Hongyun Luo ◽  
Zhiyuan Han ◽  
Linyan Zhang ◽  
Xiaoguang Yang
Keyword(s):  
Acoustic Emission ◽  
Fracture Process ◽  
Tensile Deformation ◽  
Lath Martensite ◽  
High Amplitude ◽  
High Yield ◽  
Low Alloy Steels ◽  
Continuous Type ◽  
Deformation And Fracture ◽  
Alloy Steels

The effect of different microstructures, obtained under different tempering temperatures on acoustic emission (AE) characteristics and source mechanisms during tensile deformation, was investigated in this study. Different heat treatments were carried out on hot-rolled low-alloy steels to obtain different microstructures (ferrite/pearlite, tempered martensite and tempered sorbite) and the AE was used to monitor the deformation and fracture process of samples of different types (BM, 200 °C tempered and 600 °C tempered). The results showed that the microstructure had different influences on the high amplitude burst-type signals and low amplitude continuous-type signals during the deformation and fracture process of low-alloy steels. In the 200 °C tempered sample, the continuous-type signals were enhanced by the high yield stress and dislocation velocity induced by the block of the lath martensite whose substructure was high-density dislocation. On the other hand, the interaction of the precipitates with the local dislocations increased the intensity of AE events, thus generating burst-type signals with higher amplitude in the 600 °C tempered samples.

Formation of Ultrafine Grained Ferrite by Warm Deformation of Tempered Lath Martensite in Low Alloy Steels

2007 ◽  
Vol 558-559 ◽  
pp. 557-562 ◽  
Author(s):  
Behrang Poorganji ◽  
Takuto Yamaguchi ◽  
Tadashi Maki ◽  
G. Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Grain Size ◽  
Carbon Content ◽  
Volume Fraction ◽  
Boundary Migration ◽  
Lath Martensite ◽  
Second Phase ◽  
Low Alloy Steels ◽  
Warm Deformation ◽  
Alloy Steels ◽  
Block Width

Microstructure change during warm deformation of tempered lath martensite in Fe-2mass%Mn-C alloys with different carbon contents in the range between 0.1 and 0.8mass%C was investigated. Specimens of the alloys after being quenched and tempered at 923K for 0.3ks were compressed by 50% with a strain rate varying from 10-3 to 10-4s-1 at 923K. EBSD analysis of the deformed microstructures has revealed that fine equiaxed ferrite (α) grains surrounded by high-angle boundaries are formed by dynamic recrystallization (DRX). As carbon content increases, the DRX α grain size decreases. This could be attributed to the change in volume fraction of the cementite (θ) phase as boundary dragging particles. The sub-micron θ particles can suppress the coarsening of the DRX α grains by exerting a pinning effect on grain boundary migration. Furthermore, the fraction of recrystallized region increases by increasing carbon content, presumably due to a decrease in the martensite block width as an initial α grain size and a larger volume fraction of hard second phase (θ) particles. Both of these should increase inhomogeneous plastic deformation which promotes the recrystallization. It seems that continuous DRX is responsible for the formation of ultrafine α grains in the tempered lath martensite.

Analysis of Recrystallization Behavior of Hot-Deformed Austenite Reconstructed from EBSD Orientation Maps of Lath Martensite

2016 ◽  
Vol 879 ◽  
pp. 2389-2394
Author(s):  
Manabu Kubota ◽  
Kohsaku Ushioda ◽  
Goro Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Hot Deformation ◽  
Lath Martensite ◽  
New Method ◽  
Reconstruction Method ◽  
Low Alloy Steels ◽  
Recrystallization Behavior ◽  
Compression Direction ◽  
Orientation Map ◽  
Alloy Steels ◽  
Parent Austenite

The recrystallization behavior of hot-deformed austenite of 0.55% C low alloy steels at 900, 850 and 800°C was investigated by a conventional double-hit compression test and a new method which reconstructs the parent austenite orientation map from an EBSD (electron backscattering diffraction) orientation map of daughter lath martensite. The new method can clearly reconstruct the parent austenite structure at high temperature from the daughter lath martensite structure and we can obtain the information on crystal orientation of the work-hardened austenite. It was revealed that recrystallization of austenite at 800 °C is significantly retarded by the addition of 0.1% V. The strong texture of <110> parallel to the compression direction develops just after the hot-deformation, but this texture becomes weaker as the recrystallization progresses. By applying the reconstruction method, it becomes possible to evaluate various phenomena related to the hot-deformation of austenite

Rosenhain Centenary Conference - 3. Materials development present and future 3.3 Development of line pipe steels

1976 ◽  
Vol 282 (1307) ◽  
pp. 305-318 ◽  
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
High Yield ◽  
Low Alloy Steels ◽  
Low Carbon ◽  
High Yield Strength ◽  
Line Pipe ◽  
Materials Development ◽  
Alloy Steels ◽  
Low Carbon Bainite

The demand for large diameter gas line pipe with high yield strength and high notch toughness has led to increased research in high strength low alloy steels. Physical metallurgists have developed both a fundamental and an empirical understanding of the properties and microstructures of ferrite pearlite steels. As specifications become more rigorous, alternative microstructures (low carbon bainite or tempered bainite and martensite) are being used in line pipe. There is a definite need for metallurgists to develop a clearer understanding of the interrelationships between their properties, microstructures, and processing before these alternatives are completely accepted for use in line pipe.

scholarly journals Determination of Exact Orientation Relationships between Martensite and Austenite in Steels by Microdiffraction

1981 ◽  
Vol 39 ◽  
pp. 364-365
Author(s):  
M. Sarikaya
Keyword(s):  
Lath Martensite ◽  
Crystallographic Analysis ◽  
Martensite Lath ◽  
Exact Nature ◽  
Low Alloy Steels ◽  
Martensitic Steels ◽  
Orientation Relationships ◽  
Carbon Plate ◽  
Alloy Steels

A significant number of investigations have been performed on the determination of orientation relationships (OR) in high carbon, plate-martensitic steels. However, very little is known on the exact nature of ORs in technologically important lath martensitic steels. In the present study, in a series of low alloy steels with carbon contents between 0.1-0.4 wt%, the existence of retained austenite as thin films (∼200 Å thick) around the martensite lath boundaries, makes it possible to do direct crystallographic analysis between martensite and austenite by microdiffraction.The most commonly observed orientations for lath martensite-retained γ are <111>α'//<110>γ//<100>α'. Fig. 1 shows an example of a highly symmetric SAD pattern which was interpreted as follows: Considering only one martensite lath at a time, the <lll>α' and <110>γ combination corresponds to Kurdjumov-Sachs (K-S) OR, and <110>α and <100>γ corresponds to Nishiyama-Wassermann (N-W) OR. The coexistance of these two relationships may be taken as evidence that as many variants as necessary occur to provide maximum flexibility for martensite nucleation.

Characterization of the Fracture Process of a Plate-Type Piezoelectric Composite Actuator under a Bending Load by Acoustic Emission Monitoring

2006 ◽  
Vol 326-328 ◽  
pp. 693-696
Author(s):  
Sung Choong Woo ◽  
Nam Seo Goo
Keyword(s):  
Acoustic Emission ◽  
Fracture Process ◽  
Fiber Composite ◽  
Maximum Load ◽  
High Amplitude ◽  
Piezoelectric Composite ◽  
Bending Load ◽  
Composite Actuator ◽  
Plate Type ◽  
Pzt Ceramic

Characteristics during the fracture process of a plate-type piezoelectric composite actuator (PCA) using acoustic emission (AE) monitoring were investigated under a bending load. The fracturing of a monolithic PZT ceramic shows typically brittle behavior; furthermore, the AE signal at the maximum load, which corresponds to the final fracture, has a high amplitude and long duration. Analysis of dominant frequency bands by a fast Fourier transform (FFT) in conjunction with AE parametric analysis expressed the characteristic changes of the fracture process in the PCA. For the PCA, a brittle fracture in a PZT ceramic layer induces the local delamination between the PZT ceramic and adjacent fiber composite layers. Based on the AE analysis and damage observations through optical microscopy, the features of AE associated with fracture process can be elucidated for the PCA.

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