scholarly journals The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 634
Author(s):  
Yong Tian ◽  
Hongtao Wang ◽  
Xiaoning Xu ◽  
Zhaodong Wang ◽  
R.D.K. Misra ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
High Strength ◽  
Interparticle Spacing ◽  
Grain Structure ◽  
Granular Bainite ◽  
Precipitation Strengthening ◽  
Isothermal Treatment ◽  
Strengthening Effect ◽  
Precipitation Behavior ◽  
The Impact

Isothermal treatment affects the microstructural evolution and the precipitation behavior of high-strength low alloy (HSLA) steels. In this regard, thermal simulation of different isothermal treatment temperatures was adopted by using a thermomechanical simulator. The results showed that hardness reached the maximum value at 600 °C holding temperature, which was related to a finer grain structure and granular bainite. The strengthening effect of precipitates was remarkable due to the combination of small particle size and small interparticle spacing. It is presumed that the precipitation started after 600 s at 600 °C. Precipitation strengthening continued to exist, even though coarsening of ferrite grains led to softening phenomena when the specimen was isothermally held at 750 °C, which led to relatively high hardness. The precipitates were fcc (Ti, Nb) (N, C) particles, and belonged to MX-type precipitates. Average size of precipitates increased from 3.14 to 4.83 nm when the specimens were isothermally held between 600 °C and 800 °C. Interparticle spacing of precipitates also increased with increasing isothermal treatment temperatures. These led to a reduction in precipitation strengthening. At the same time the polygonal ferrite content increased and ferrite grain size got larger, such that the hardness decreased continuously.

Nano-Scaled Fe3C Precipitates and Precipitation Strengthening in Hot Rolled Low Carbon High Strength Titanium Microalloyed Steel

2010 ◽  
Vol 146-147 ◽  
pp. 838-843
Author(s):  
Jian Feng Wang ◽  
Guang Qiang Li ◽  
Ai Da Xiao ◽  
Fu Jie
Keyword(s):  
Yield Strength ◽  
Microalloyed Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Precipitation Strengthening ◽  
Strengthening Effect ◽  
Low Carbon ◽  
High Resolution Tem ◽  
Bainite Microstructure ◽  
Hot Rolled

Hot rolled Ti microalloyed steel with polygonal ferrite and granular bainite microstructure and 640 MPa yield strength has been developed in BOF-CSP process. By chemical phase analysis, XRD, EDS and high resolution TEM, the particle size distribution, morphology, composition, crystal structure of precipitates were identified. Results revealed the steel containing Ti exhibits fine and uniformly distributed Fe3C-type carbides, the amount of M3C particles less than 18 nm in size was 0.2565 mass %. The high strength of steel is attributed to the precipitation strengthening effect of Fe3C, the yield strength increment from precipitation strengthening of Fe3C calculated according to the formula by Olson and Ashby-Orowan attained 234.4 MPa.

Microstructure and Mechanical Properties of X70 Pipeline Steel with High H2S Resistance

2015 ◽  
Vol 816 ◽  
pp. 755-760 ◽  
Author(s):  
Jing Li ◽  
Xiu Hua Gao ◽  
Yong Lu ◽  
Lin Xiu Du
Keyword(s):  
Mechanical Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Second Phase ◽  
Precipitation Behavior ◽  
Experimental Steel ◽  
X70 Pipeline Steel ◽  
The Matrix ◽  
Sour Service

Anti-H2S X70 pipeline steel was developed. The microstructure of X70 pipeline steel was studied by the analysis of OM, SEM and TEM. The precipitation behavior was discussed. The comprehensive mechanical properties, HIC and SCC performance were systematically studied. The results indicated that the microstructure of the experimental steel was mainly acicular ferrite and granular bainite. The second phase precipitates dispersedly distributed in the matrix. The experimental steel possessed excellent strength, plasticity, low temperature toughness and low yield ratio. And therefore, the X70 pipeline steel in the study is suitable for sour service with the high strength, excellent toughness and low HIC&SSC susceptibility.

scholarly journals Multimodal Microstructure and Mechanical Properties of AZ91 Mg Alloy Prepared by Equal Channel Angular Pressing plus Aging

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 763 ◽  
Author(s):  
Zhenquan Yang ◽  
Aibin Ma ◽  
Huan Liu ◽  
Jiapeng Sun ◽  
Dan Song ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Magnesium Alloys ◽  
High Strength ◽  
Cost Effective ◽  
Back Stress ◽  
Grain Structure ◽  
Mg Alloy ◽  
Precipitation Strengthening ◽  
Processing Route ◽  
Good Ductility

Developing cost-effective magnesium alloys with high strength and good ductility is a long-standing challenge for lightweight metals. Here we present a multimodal grain structured AZ91 Mg alloy with both high strength and good ductility, prepared through a combined processing route of low-pass ECAP with short-time aging. This multimodal grain structure consisted of coarse grains and fine grains modified by heterogeneous precipitates, which resulted from incomplete dynamic recrystallization. This novel microstructure manifested in both superior high strength (tensile strength of 360 MPa) and good ductility (elongation of 21.2%). The high strength was mainly attributed to the synergistic effect of grain refinement, back-stress strengthening, and precipitation strengthening. The favorable ductility, meanwhile, was ascribed to the grain refinement and multimodal grain structure. We believe that our microstructure control strategy could be applicable to magnesium alloys which exhibit obvious precipitation strengthening potential.

scholarly journals Low Temperature Deformation Induced Microstructure Refinement and Consequent Ultrahigh Toughness of a 20Mn2SiCrNi Bainitic Steel

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 19 ◽  
Author(s):  
Yu Tian ◽  
Zhunli Tan ◽  
Ji Li ◽  
Bo Gao ◽  
Min Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
High Strength Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Temperature Deformation ◽  
Air Cooling ◽  
Degree Of Deformation ◽  
Lower Temperature ◽  
The Impact

In this paper, we have studied the influence of deformation on the microstructure and mechanical properties of 20Mn2SiCrNi bainitic high strength steel processed through a hot rolling route. Simulation of different temperatures and degrees of deformation was carried out via Gleeble-1500. The study suggested that grain size is refined when the deformation is carried out at lower temperature (> Ac3). When the degree of deformation was increased from 20% to 60%, grain size and microstructure were both refined and the size of retained austenite was reduced. The tensile strength increased from 1345 MPa to 1432 MPa. The impact toughness increased from 115 J/cm2 to 210 J/cm2 at room temperature, from 63 J/cm2 to 142 J/cm2 at −40 °C. Furthermore, it was observed that the microstructure after air cooling was composed of granular bainite (GB), lath bainite (LB) and martensite/austenite (MA) island for different deformation conditions. The study reveals that the impact toughness of 20Mn2SiCrNi bainitic high strength steel can be increased by increasing the degree of deformation.

Charpy Impact Properties of Grain Boundary Allotriomorphic Ferrite and Granular Bainite Duplex Microstructure

2014 ◽  
Vol 1004-1005 ◽  
pp. 1236-1244 ◽  
Author(s):  
Ping Luo ◽  
Gu Hui Gao ◽  
Xiao Lu Gui ◽  
Bai Feng An ◽  
Zhun Li Tan ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Grain Boundary ◽  
Crack Path ◽  
High Strength ◽  
Propagation Path ◽  
Granular Bainite ◽  
Air Cooling ◽  
Low Carbon ◽  
Allotriomorphic Ferrite ◽  
The Impact

A new type of high strength and low cost bainitic steel with ultra-low carbon content and high Si content has been developed on the basis of Mn-series air-cooling bainitic steels. The tensile properties of YS>690MPa and the impact toughness of AKV>60J at-40°C were obtained by controlling the processing parameters. This was attributed to the formation of the grain boundary allotriomorphic ferrite (FGBA) and the granular bainite (GB) with different shape of M/A islands. The high strength due to the inter-lath lamellar M/A islands or retained austenite companying with high dislocated bainitic ferrite laths of average 300nm width. The effect of microstructure on the impact crack initiation and propagation was studied. The results showed that crack initiation occurred in two different types of sites: at interphase boundaries of bainite ferrite (BF) and M/A islands, at grain boundaries. The FGBA and bainite ferrite (BF) both had blunting effect on microcrack tip to reduce the crack propagation path. Because of the presence of FGBA, the unit crack path was short, at less than 5μm. The blunting effect of BF could be enhanced by the M/A islands, which force the cracks change the propagation path and reduce the unit crack path to less than the size of bainite packets. The mechanism of low temperature microcrack origin of the ultra-low carbon bainitic (ULCB) steel with the microstructure of the FGBA and GB was also discussed.

A Study of the Microstructural Evolution and Strengthening Effects of Non-Spherical Precipitates in an Al-Cu-Based Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 2317-2320
Author(s):  
Julien da Costa Teixeira ◽  
Laure Bourgeois ◽  
Christopher R. Hutchinson
Keyword(s):  
Microstructural Evolution ◽  
Classical Case ◽  
Precipitation Strengthening ◽  
Strengthening Effect ◽  
Microstructure Design ◽  
Plate Shape ◽  
Microstructure Parameters ◽  
Isothermal Ageing

The microstructural evolution and associated strengthening during isothermal ageing of an Al-3Cu-0.05Sn reinforced by non-spherical θ' (Al2Cu) precipitates is studied. Emphasis is placed on the plate shape of the θ'. It is found that the microstructure parameters governing the magnitude of the precipitation strengthening effect are completely different from the classical case of spherical precipitates. New possibilities for microstructure design are discussed.

scholarly journals Effect of Welding Peak Temperature on Microstructure and Impact Toughness of Heat-Affected Zone of Q690 High Strength Bridge Steel

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2981
Author(s):  
Yue Zhang ◽  
Jun Xiao ◽  
Wei Liu ◽  
Aimin Zhao
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Lath Martensite ◽  
Testing Machine ◽  
High Strength ◽  
Peak Temperature ◽  
Granular Bainite ◽  
Fine Grain ◽  
Bridge Steel ◽  
The Impact

The effect of peak temperature (TP) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble-3500 thermal simulation testing machine. The results show that the microstructure of the inter critical heat-affected zone (ICHAZ) was ferrite and bainite. The microstructure of fine grain heat-affected zone (FGHAZ) and coarse grain heat-affected zone (CGHAZ) was lath bainite (LB) LB, lath martensite (LM), and granular bainite (GB), but the microstructure of FGHAZ was finer. With the increase in peak temperature, the content of LB and GB decreased, the content of LM increased, and the lath bundles of LM and LB gradually became coarser. With the increase in peak temperature, the grain size of the original austenite increased significantly, and the impact toughness decreased significantly. When the peak temperature was 800 °C, the toughness was the best. For CGHAZ, the peak temperature should be less than 1200 °C to avoid excessive growth of grain and reduction of mechanical property.

Microstructural and Mechanical Behaviour Evaluation of Mg-Al-Zn Alloy Friction Stir Welded Joint

2020 ◽  
Vol 17 (3) ◽  
pp. 8150-8159
Author(s):  
Kulwant Singh ◽  
Gurbhinder Singh ◽  
Harmeet Singh
Keyword(s):  
Heat Treatment ◽  
Friction Stir Welding ◽  
Magnesium Alloys ◽  
Mechanical Performance ◽  
Fuel Efficiency ◽  
Research Work ◽  
Grain Structure ◽  
Tensile Fracture ◽  
Friction Stir ◽  
The Impact

The weight reduction concept is most effective to reduce the emissions of greenhouse gases from vehicles, which also improves fuel efficiency. Amongst lightweight materials, magnesium alloys are attractive to the automotive sector as a structural material. Welding feasibility of magnesium alloys acts as an influential role in its usage for lightweight prospects. Friction stir welding (FSW) is an appropriate technique as compared to other welding techniques to join magnesium alloys. Field of friction stir welding is emerging in the current scenario. The friction stir welding technique has been selected to weld AZ91 magnesium alloys in the current research work. The microstructure and mechanical characteristics of the produced FSW butt joints have been investigated. Further, the influence of post welding heat treatment (at 260 °C for 1 h) on these properties has also been examined. Post welding heat treatment (PWHT) resulted in the improvement of the grain structure of weld zones which affected the mechanical performance of the joints. After heat treatment, the tensile strength and elongation of the joint increased by 12.6 % and 31.9 % respectively. It is proven that after PWHT, the microhardness of the stir zone reduced and a comparatively smoothened microhardness profile of the FSW joint obtained. No considerable variation in the location of the tensile fracture was witnessed after PWHT. The results show that the impact toughness of the weld joints further decreases after post welding heat treatment.

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