Hot Ductility Behavior of 800MPa Ultra High Strength Niobium Containing Steels

2013 ◽  
Vol 690-693 ◽  
pp. 227-232
Author(s):  
Qing Shan Li ◽  
Mei Zhang ◽  
Chao Bin Huang ◽  
Ru Yi Wu ◽  
Xue Zhao ◽  
...  
Keyword(s):  
Film Formation ◽  
True Strain ◽  
High Strength ◽  
Fracture Morphology ◽  
Hot Ductility ◽  
Ferrite Film ◽  
True Strain Rate ◽  
The Third ◽  
Brittle Zone ◽  
Austenite Grain Boundary

The hot ductility behavior of 800MPa ultra high strength niobium containing steels has been investigated with Gleeble3500 hot simulator. Tensile test was carried out at 650°C1300°C at a constant true strain rate of 0.001 s1. Experimental results showed that steel A has quite well ductility, and the brittle zone is narrow. Due to pro-eutectoid ferrite film formation along the prior austenite grain boundary at 650°C-750°C, samples showed a loss of hot ductility, and the fracture morphology of the specimens was brittle intercrystalline fracture, indicating the third brittle zone of the steel. However, the third brittle zone can be avoided during continuous casting, if the temperature of straightening could be kept over 800°C.

Hot Ductility of Low Carbon Nb-Microalloyed Weathering Steel

2014 ◽  
Vol 887-888 ◽  
pp. 200-206 ◽  
Author(s):  
Mei Zhang ◽  
Xue Zhao ◽  
Yan Zhu ◽  
Chao Bin Huang ◽  
Qing Shan Li ◽  
...  
Keyword(s):  
Electron Microscope ◽  
True Strain ◽  
Optical Microscope ◽  
Weathering Steel ◽  
Hot Ductility ◽  
Ferrite Film ◽  
Low Carbon ◽  
True Strain Rate ◽  
The Third ◽  
Brittle Zone

High temperature tensile tests of novel developed Nb-microalloyed weathering steels were carried out with a constant true strain rate of 0.001/s at 650°C-1300°C using Gleeble3500 thermo-mechanical simulator. The tensile strength (TS) and reduction in area (RA) were calculated afterwards to obtain hot ductility curve and hot strength curve of the steel. The hot ductility behaviors were studied in detail under optical microscope (OM), scanning electron microscope (SEM) and transition electron microscope (TEM). The third brittle zone of the studied steels was between 650°C-800°C. SEM fractographs and microstructures of the tensile specimen showed that the occurrence of the third brittle zone was mainly related to the formation of pro-eutectoid ferrite film along the prior austenite grain boundaries, and secondly to the precipitation of second phases. Therefore, it was recommended that the straightening temperature of the studied steel after casting should be kept over 800°C to get crack free continuous casting (CC) slabs.

Research on Hot Ductility Behavior of 800 MPa Grade Ultra High Strength Weathering Steel

2013 ◽  
Vol 815 ◽  
pp. 205-211
Author(s):  
Chao Bin Huang ◽  
Yan Zhu ◽  
Ru Yi Wu ◽  
Qing Shan Li ◽  
Mei Zhang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
High Strength ◽  
Weathering Steel ◽  
Second Phase ◽  
Hot Ductility ◽  
The Third ◽  
Test Steel ◽  
Brittle Zone ◽  
Gleeble 3500 ◽  
Austenite Grain Boundary

The hot ductility behavior of test steel was investigated by Gleeble-3500 thermo-mechanical simulator through high temperature tensile test. The reduction in area (RA) and tensile strength (TS) were acquired to draw hot ductility curve and hot strength curve. SEM fractograph and microstructure of the tensile samples were analyzed. The results show that the third brittle zone of test steel is between 700°C and 800°C and the occurrence of the third brittle zone is mainly related to the formation of film-like ferrite along the prior austenite grain boundary and the precipitation of second phase. Moreover, the drop of hot ductility at 900°C is rooted in the reduction of grain boundary strength owing to the precipitation of sulfides. Therefore, it is advised that the straightening temperature of test steel should be kept over 900°C.

Influence of Different Levels of Cu Equivalent on the Hot Ductility of 20CrMnTi Steel

2015 ◽  
Vol 34 (5) ◽  
Author(s):  
Hong-bing Peng ◽  
Wei-qing Chen ◽  
Lie Chen ◽  
Dong Guo
Keyword(s):  
Copper Sulfide ◽  
Fracture Morphology ◽  
Hot Ductility ◽  
Ferrite Film ◽  
Austenite Grain ◽  
Ductility Trough ◽  
Proeutectoid Ferrite ◽  
Austenite Grain Boundary ◽  
Fine Copper ◽  
Different Levels

AbstractThe hot ductility of 20CrMnTi steel with different levels of Cu equivalent was investigated. The results show that Sn and Cu in 20CrMnTi steel are detrimental to its hot ductility. Sn was found to segregate to the boundaries tested by EPMA, moreover, Cu was not found to segregate to boundaries, however, the fracture morphology was examined with SEM and showed many small and shallow dimples on the fracture of steels with large Cu equivalent (>0.15) and fine copper sulfide was found from carbon extraction replicas using TEM. The adverse effect of large Cu equivalent (>0.15) on the hot ductility was due to Sn segregation and fine copper sulfide in the steel as well as their retarding the occurrence of dynamic recrystallization (DRX). The proeutectoid ferrite film precipitating along the austenite grain boundary causes the ductility trough of the five examined steels. Moreover, in this case, the level of Cu equivalent should be controlled below 0.15, which would not deteriorate the hot ductility significantly.

Structural and Mechanical Features of Rapidly Solidified Al-2Fe-2Ni-5Mg Alloy

2012 ◽  
Vol 186 ◽  
pp. 279-282 ◽  
Author(s):  
Anna Kula ◽  
Ludwik Blaz ◽  
Makoto Sugamata
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
Spray Deposition ◽  
True Strain ◽  
Hot Extrusion ◽  
High Strength ◽  
Solid Solution Hardening ◽  
Compression Tests ◽  
Dispersion Strengthening ◽  
True Strain Rate

Rapid solidification (RS) of Al-2Fe-2Ni-5Mg alloy and following mechanical consolidation of powders by means of powder metallurgy (PM) methods was used with success to produce a bulk RS-material. RS powders were manufactured using an inert gas atomizing of the molten alloy and the spray deposition on the rotating water-cooled copper roll. Rods of 7 mm in diameter were received by means of the cold pressing of the flakes, vacuum degassing and hot extrusion method. For comparison purposes, the conventionally casted and hot extruded Al-2Fe-2Ni-5Mg alloy was tested as well. Mechanical properties of as-extruded materials were examined at 293 K – 873 K by compression tests performed at constant true strain rate of 5·10-3[s-1]. It was found that relatively high strength of as-extruded RS/PM material was accompanied by the high ductility of the samples deformed by hot compression tests. It was noticed that the most effective solution strengthening due to particles refining was observed at low deformation temperatures. Rising the test temperatures above ~ 420 K, was found to result in reduction of the flow stress to the values received for the industrial material (IM).The formation of coarse primary intermetallic compounds, which is typical for IM material, was effectively reduced for RS material. However some inhomogeneity of fine precipitates distribution in RS/PM material was observed. Nevertheless, it was considered that both solid solution hardening due to Mg addition and the dispersion strengthening due to refining of intermetallic compounds substantially increase the mechanical properties of the RS/PM material.

INFLUENCE OF NITROGEN ON HOT DUCTILITY BEHAVIOR OF MEDIUM CARBON MICROALLOYED STEEL

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1122-1128 ◽  
Author(s):  
SUJUAN ZHAO ◽  
QINGFENG WANG ◽  
ZESHENG YAN
Keyword(s):  
Microalloyed Steel ◽  
True Strain ◽  
Tensile Tests ◽  
Microalloyed Steels ◽  
Hot Ductility ◽  
True Strain Rate ◽  
Medium Carbon ◽  
Ductility Trough ◽  
Carbon Microalloyed

The current study aims to estimate the influence of enhanced nitrogen on the hot ductility of medium carbon microalloyed steel. For this purpose, hot tensile tests were carried out at temperatures rangeing from 700°C-1000°C at a true strain rate of 0.001s-1. The fracture surfaces and their neighboring precipitates and matrix microstructures "frozen" in tensile temperatures were observed. The dependence of hot ductility on the fracture mode and in situ microstructural changes were discussed. The results indicate that raising the nitrogen content from 0.003% to 0.014% and 0.021% was found to deteriorate the ductility as the obtained ductility trough became deeper and wider. The trough deepening caused by the addition of nitrogen was due to the formation of film-like ferrite and fine VN precipitation along the austenite grain boundaries promoting low ductility intergranular failure. On the other hand, the retarded dynamic recrystallization, the promoted deformation induced ferrite formation and precipitation at higher temperatures by enhanced nitrogen were regarded as the possible reasons for a wider trough. In summary, the above results indicate the hot ductility of medium carbon microalloyed steels is weakened to some extent by enhanced nitrogen and their windows suitable for continuous casting should be schemed very carefully.

scholarly journals High-Temperature Mechanical Properties of 4.5%Al δ-TRIP Steel

2019 ◽  
Vol 9 (23) ◽  
pp. 5094
Author(s):  
Dayu Chen ◽  
Heng Cui ◽  
Rudong Wang
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
High Temperature ◽  
Grain Boundary ◽  
Trip Steel ◽  
Scanning Calorimetry ◽  
The Third ◽  
High Temperature Mechanical Properties ◽  
Brittle Zone ◽  
Austenite Grain Boundary

The high-temperature mechanical properties of a 4.5% Al-containing δ-transformation-induced plasticity (TRIP) steel were studied by using the Gleeble 3500 thermomechanical simulator. The zero ductility temperature (ZDT) and the zero strength temperature (ZST) were measured, and the brittle zones were divided. The phase transformation zone was determined by differential scanning calorimetry (DSC). The temperature of the phase transformation and the proportion of the phase were calculated by the Thermo-Calc software. The ZDT and the ZST of the 4.5% Al-containing δ-TRIP steel are 1355 and 1405 °C, respectively. The first brittle zone and the third brittle zone of the steel are 1300–1350 °C and 800–975 °C, respectively. The reason for the embrittlement of the third brittle zone of the 4.5% Al-containing δ-TRIP steel is that the α-ferrite formed at the austenite grain boundary causes the sample to crack along the grain boundary under stress. The ductility of the 4.5% Al-containing δ-TRIP steel decreases first and then increases with the increase of the α-ferrite. When the proportion of the α-ferrite reaches 37%, the reduction of area (RA) of the 4.5% Al-containing δ-TRIP steel is reduced to 44%. The 4.5% Al-containing δ-TRIP steel has good resistance to the high-temperature cracking.

Structure Evolution in Annealed and Hot Deformed AlMg-CeO2 Composite

2016 ◽  
Vol 682 ◽  
pp. 259-264 ◽  
Author(s):  
Tomasz Skrzekut ◽  
Anna Kula ◽  
Ludwik Blaz
Keyword(s):  
Elevated Temperatures ◽  
True Strain ◽  
High Strength ◽  
Mechanical Tests ◽  
Solid State Reactions ◽  
Structure Evolution ◽  
Compression Tests ◽  
Mechanically Alloyed ◽  
True Strain Rate ◽  
The Matrix

A brief review of structural investigation and results of mechanical tests for mechanically alloyed AlMg-based composite reinforced with 9 wt.% addition of CeO2 is presented. The as extruded and annealed samples were examined by means of SEM, TEM and X-ray analysis. Heavily refined matrix grains and particles of cerium oxides were observed in the as extruded material. Fine microstructure attained by mechanical alloying and high affinity of oxygen to aluminum-magnesium matrix results in promoted solid state reactions between the matrix and reinforcements at elevated temperatures. Consequently, Al4Ce intermetallic grains and Al/Mg oxides are formed in the result of CeO2 decomposition. Hot compression tests were performed at constant true strain rate of 5·10-3 s-1 within the temperature range of 293 – 823K. Highly refined structure of the material was found to result in high strength of the composite, particularly for samples tested at low and intermediate temperatures.

Comparative Study of Various Data Conversion Methods for Torsion Tests Applied to a HSLA Steel

2010 ◽  
Vol 638-642 ◽  
pp. 3164-3169
Author(s):  
Jesus Castellanos ◽  
Ignacio Rieiro ◽  
Manuel Carsí ◽  
Julio Muñoz ◽  
Oscar A. Ruano
Keyword(s):  
Flow Behavior ◽  
Hsla Steel ◽  
True Strain ◽  
High Strength ◽  
Data Conversion ◽  
Strain Rates ◽  
Peak Strain ◽  
True Strain Rate ◽  
A Value ◽  
Different Strains

The influence of methods for converting torsion data (torque, number of turns and speed rotation) into equivalent variables (true stress, true strain and true strain rate) on the Garofalo equation parameters is studied. Torsion tests for a high strength low alloy steel at temperatures in the range 900 to 1150°C and strain rates in the range 0.5 to 30 s-1 were conducted. The flow behavior of the material was analyzed by means of the Garofalo equation which is especially adequate for the correlation of torsion data in wide ranges of temperatures and strain rates. The Garofalo equation was fitted at different strains: from peak strain to a value of strain where a steady-state is assumed. The parameters of this equation, A, Q, n, , were determined by the RCR method which does not need initial values and provides coefficients indicating the quality of the fitting. Finally, the Garofalo equation parameters were related to creep mechanisms operating in this steel.

scholarly journals Microstructural Characterization and Mechanical Property of Al-Li Plate Produced by Centrifugal Casting Method

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 966
Author(s):  
Qingle Tian ◽  
Kai Deng ◽  
Zhishuai Xu ◽  
Ke Han ◽  
Hongxing Zheng
Keyword(s):  
Centrifugal Casting ◽  
High Strength ◽  
Microstructural Characterization ◽  
Fracture Morphology ◽  
Total Elongation ◽  
Mechanical Anisotropy ◽  
Tensile Fracture ◽  
Casting Method ◽  
Scanning Calorimetry ◽  
Strengthening Phases

Using a centrifugal casting method, along with deformation and aging, we produced a high-strength, low-anisotropy Al-Li plate. The electron probe microanalysis, transmission electron microscope, differential scanning calorimetry, and X-ray diffraction were used to clarify the evolution of strengthening phases. Experimental results showed that centrifugal-cast Al-Li plate consisted of intragrain δ′—(Al,Cu)3Li precipitate and interdendritic θ′—Al2Cu particles. After cold-rolling to a reduction ratio of 60% and annealing at 800 K for 90 min, both primary θ′ and δ′ were dissolved in solid solution. Aging at 438 K for 60 h led to the formation of two kinds of precipitates (needle-like T1—Al2CuLi and spherical δ′ in two sizes), which acted as the main strengthening phases. The average values of ultimate tensile strength and yield strength for the anneal-aged plate reached 496 MPa and 408 MPa, with a total elongation of 3.9%. The anneal-aged plate showed mechanical anisotropy of less than 5%. The tensile fracture morphology indicated a typical intergranular fracture mode.

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