Effect of Thermomechanical Parameters on the Microstructure and Retained Austenite Characteristics in a Hot-Rolled TRIP Steel

2011 ◽  
Vol 295-297 ◽  
pp. 1294-1299
Author(s):  
Yun Yang Yin ◽  
Fang Fang ◽  
Wei Chen ◽  
Yong Tao Fu
Keyword(s):  
Strain Rate ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
Minor Effect ◽  
Coiling Temperature ◽  
Hot Rolled ◽  
Undercooled Austenite

The influence of thermomechanical parameters on the microstructure and retained austenite characteristics in a hot rolled Al-Si-Mn transformation induced plasticity (TRIP) steel based on dynamic transformation of undercooled austenite was investigated, in an effort to produce a desired microstructure and better control retained content. The results show that strain rate had a minor effect on the microstructure, but the volume fraction of retained austenite decreased with increasing strain rate. Decreasing coiling temperature caused a decrease in volume fraction of retained austenite and decrease in the size of bainitic ferrite platelets. Increasing the isothermal holding time during bainite treatment, the volume fraction of retained austenite first gradually increased then decreased. Moreover, The deformation of undercooled austenite not only can influenc the transformation of bainite, but also can refine the grain size of bainite, increase the chemical and mechanical stabilization of retained austenite.

Microstructure and Mechanical Properties of Hot Rolled TRIP Steel Based on Dynamic Transformation of Undercooled Austenite

2010 ◽  
Vol 152-153 ◽  
pp. 1038-1043
Author(s):  
Yun Yang Yin ◽  
Fang Fang ◽  
Zhi Jin Fan
Keyword(s):  
Electron Microscopy ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Volume ◽  
Ferrite Matrix ◽  
Total Elongation ◽  
Dynamic Transformation ◽  
Hot Rolled ◽  
Undercooled Austenite

The microstructure characteristics and tensile properties in a 0.2C-1.5Mn-1.0Al-0.50Si, high strength hot rolled TRIP steel obtained by a new processing based on dynamic transformation of undercooled austenite(DTUA) were investigated. The results show that the main feature of the new technology is that the ferrite was produced by the applied strain during DTUA. Characterization by means of optical and scanning electron microscopy, transmission electron microscopy and X-ray diffraction has shown that the microstructure of the investigated steel contained a ferrite matrix with fine grain size, bainite with small bainitic packets, and high volume fraction of retained austenite with a large number of granular retained austenite. Tensile testing indicates the steels produced by this processing have higher strength (790MPa) and total elongation (35%) as well as low yield ratio..

Effect of Al on the Microstructure and Mechanical Properties of Hot-Rolled Medium-Mn Steel

2018 ◽  
Vol 941 ◽  
pp. 292-298 ◽  
Author(s):  
Ding Ting Han ◽  
Yun Bo Xu ◽  
Ying Zou ◽  
Zhi Ping Hu ◽  
Shu Qing Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Trip Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Microstructure And Mechanical Properties ◽  
Medium Mn Steel ◽  
Hot Rolled ◽  
Mn Steel

The present investigation was made to study the effect of Al on the microstructure and mechanical properties of hot-rolled medium-Mn TRIP steel (abbreviated as Al-TRIP). As a contrast, a Si-added medium-Mn TRIP steel (abbreviated as Si-TRIP) was also studied. Addition Al in medium-Mn steel can raise Ac3 temperature, which will restrain austenite transformation and expand the two-phase region, promoting Mn and C elements enriched in austenite. In-depth microstructure and mechanical properties analysis were carried out for the hot-rolled Al-TRIP and Si-TRIP steels in this study. The microstructure was characterized by scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). Volume fraction of retained austenite was measured by D/max2400 X-ray diffractometer (XRD). A dual-phase microstructure consisting of ultra-fine grained intercritical ferrite (IF) and lath-like retained austenite (RA) with high mechanical stability was obtained after annealing at 630°C for 2h for Al-TRIP steel. As prolonging the intercritical annealing time, the stability of RA decreased primarily due to the increase of grain size. The tensile test results indicated that the Al-TRIP steel possessed a better combination of tensile strength and elongation compared to Si-TRIP steel. Excellent mechanical properties with yield strength of 790MPa, tensile strength of 1050MPa, total elongation of 35% and UTS×TEL of 39GPa·% was obtained for the Al-TRIP steel.

scholarly journals Effect of Quenching and Partitioning Temperatures in the Q-P Process on the Properties of AHSS with Various Amounts of Manganese and Silicon

2012 ◽  
Vol 706-709 ◽  
pp. 2734-2739 ◽  
Author(s):  
Hana Jirková ◽  
Ludmila Kučerová ◽  
Bohuslav Mašek
Keyword(s):  
Tensile Strength ◽  
Retained Austenite ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Program ◽  
Quenching Temperature ◽  
Quenching And Partitioning ◽  
Advanced High Strength Steels

The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.

Effect of Different Coiling Temperature on Mechanical Properties in Hot Rolled TRIP Steel

2011 ◽  
Vol 239-242 ◽  
pp. 1092-1095
Author(s):  
Xu Tao Gao ◽  
Ai Min Zhao ◽  
Zheng Zhi Zhao ◽  
Ming Ming Zhang ◽  
Di Tang
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
X Ray Diffraction ◽  
Coiling Temperature ◽  
Experimental Steel ◽  
Transformation Induced Plasticity ◽  
X Ray ◽  
Trip Steels ◽  
Hot Rolled ◽  
Scanning Electron

By means of optical microscopy(OM), scanning electron microscopy(SEM),X-ray diffraction(XRD),And tensile test, Mechanical Properties of hot rolled transformation -induced plasticity (TRIP) steels which were prepared through three different coiling temperature was investigated. Result reveals that the formability index of the experimental steel descends when the coiling temperature becomes low. Different coiling temperature has greater impact on retained austenite. Amount and carbon content of retained austenite in the experimental steel get less with lower coiling temperature.

Microstructure and Tensile Properties of TRIP-Aided Steel Sheet Subjected to Hot-Rolling and Austempering

2021 ◽  
Vol 1016 ◽  
pp. 732-737
Author(s):  
Junya Kobayashi ◽  
Hiroto Sawayama ◽  
Naoya Kakefuda ◽  
Goroh Itoh ◽  
Shigeru Kuraoto ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Hot Rolling ◽  
Manufacturing Process ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Isothermal Holding ◽  
High Strength ◽  
Isothermal Transformation ◽  
Transformation Process ◽  
Steel Sheets

Various high strength steel sheets for weight reduction and safety improvement of vehicles have been developed. TRIP-aided steel with transformation induced plasticity of the retained austenite has high strength and ductility. Conventional TRIP-aided steels are subjected to austempering process after austenitizing. Generally, elongation and formability of TRIP-aided steel are improved by finely dispersed retained austenite in BCC phase matrix. The finely dispersed retained austenite and grain refinement of TRIP-aided steel can be achieved by hot rolling with heat treatment. Therefore, the improvement of mechanical properties of TRIP-aided steel is expected from the manufacturing process with hot rolling and then isothermal transformation process. In this study, thermomechanical heat treatment is performed by combining hot rolling and isothermal holding as the manufacturing process of TRIP-aided steel sheets. The complex phase matrix is obtained by hot rolling and then isothermal holding. Although the hardness of the hot rolled and isothermal held TRIP-aided steel is decreased, the volume fraction of retained austenite is increased.

Isothermal Transformation, Microstructure and Mechanical Properties of Ausformed Low-Carbon Carbide-Free Bainitic Steel

2018 ◽  
Vol 941 ◽  
pp. 329-333 ◽  
Author(s):  
Jiang Ying Meng ◽  
Lei Jie Zhao ◽  
Fan Huang ◽  
Fu Cheng Zhang ◽  
Li He Qian
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Isothermal Transformation ◽  
Bainitic Transformation ◽  
Isothermal Treatment ◽  
Bainitic Steel ◽  
Low Carbon ◽  
Microstructure And Mechanical Properties

In the present study, the effects of ausforming on the bainitic transformation, microstructure and mechanical properties of a low-carbon rich-silicon carbide-free bainitic steel have been investigated. Results show that prior ausforming shortens both the incubation period and finishing time of bainitic transformation during isothermal treatment at a temperature slightly above the Mspoint. The thicknesses of bainitic ferrite laths are reduced appreciably by ausforming; however, ausforming increases the amount of large blocks of retained austenite/martenisite and decreases the volume fraction of retained austenite. And accordingly, ausforming gives rise to significant increases in both yield and tensile strengths, but causes noticeable decreases in ductility and impact toughness.

scholarly journals Microstructure and Mechanical Properties of Tempered Ausrolled Nanobainite Steel

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 573
Author(s):  
Jing Zhao ◽  
Dezheng Liu ◽  
Yan Li ◽  
Yongsheng Yang ◽  
Tiansheng Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Energy Yield ◽  
Partial Recovery ◽  
Fracture Appearance ◽  
The Impact

The microstructures and mechanical properties of ausrolled nanobainite steel, after being tempered at temperatures in the range of 200−400 °C, were investigated in this study. After being tempered, bainitic ferrite is coarsened and the volume fraction of retained austenite is reduced. The hardness and ultimate tensile strength decrease sharply. The impact energy, yield strength, and elongation increase with elevated tempered temperature at 200–300 °C but decrease with elevated tempered temperature when the samples are tempered at 350 °C and 400 °C. The fracture appearance of all the samples after impact tests is a brittle fracture. The variation of the mechanical properties may be due to partial recovery and recrystallization.

Spark Plasma Sintering and Strength Behavior under Compressive Loading of Mg-PSZ/Al2O3-TRIP-Steel Composites

2015 ◽  
Vol 825-826 ◽  
pp. 182-188 ◽  
Author(s):  
Lutz Krüger ◽  
Steffen Grützner ◽  
Sabine Decker ◽  
Ines Schneider
Keyword(s):  
Strain Rate ◽  
Spark Plasma Sintering ◽  
Trip Steel ◽  
Volume Fraction ◽  
Compressive Yield Strength ◽  
Strain Rates ◽  
Steel Matrix ◽  
Trip Effect ◽  
Plasma Sintering ◽  
Spark Plasma

Composite materials, which consist of a metastable austenitic TRIP-steel matrix (CrMnNi TRIPsteel; TRansformation Induced Plasticity) reinforced by alumina particles (25 vol.% ceramic, designated as AT 25/75) and reinforced by alumina and MgO partially stabilized zirconia particles (Mg-PSZ) (35 vol.% ceramic, designated as AT 25/75 + MgPSZ) were synthesized through spark plasma sintering (SPS). In the AT 25/75 + MgPSZ, the steel particles were mainly surrounded by alumina. Hence, mostly steel/alumina and alumina/MgPSZ interfaces existed. The mechanical behavior of the as-sintered samples was characterized by compression tests at room temperature and 40 °C and in a range of strain rates between 103s-1and 103s1. The influence of the ceramic content, strain rate and temperature on TRIP-effect of the steel matrix was investigated. Due to the increasing ceramic volume fraction, AT 25/75 + MgPSZ exhibits the highest compressive yield strength under all loading conditions and no strain rate sensitivity. This composite showed no measurable TRIP-effect, due to the low fracture strain. The deformation-induced α’martensite within the steel particles in pure steel and AT 25/75 primary depends on the testing temperature and the strain rate. This is attributed to an increase of stacking fault energy with rising temperature. High strain rates cause adiabatic heating, counteracting the martensitic transformation.

scholarly journals Formation of Medium Carbon TRIP Steel Microstructure During Annealing in the Intercritical Temperature Range

2014 ◽  
Vol 59 (3) ◽  
pp. 1017-1022 ◽  
Author(s):  
A. Kokosza ◽  
J. Pacyna
Keyword(s):  
Trip Steel ◽  
Retained Austenite ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Austenite Formation ◽  
Two Phase ◽  
Intercritical Temperature Range ◽  
Steel Microstructure ◽  
Intercritical Temperature ◽  
Temperature Range

Abstract The paper presents the results of research conducted on austenite formation in the microstructure of 41MnSi6-5 TRIP steel during annealing in the intercritical temperature range. The influence of the annealing temperature on the volume fraction of retained austenite in the microstructure of the investigated steel after water quenching was also determined.Based on the results of a dilatometric analysis and metallographic investigation it was noted that the pearlite-to-austenite transformation does not occur at a constant temperature, which is referred to as Ac1, but rather within some, possible to determine, temperature range which is bounded by the values Ac1s and Ac1f.Moreover, through X-ray analysis, it was stated that the largest amount of retained austenite remained in the samples which were annealed at the lowest temperatures in the Ac1s-Ac1f range prior to quenching. Increasing the annealing temperature to a two-phase a+g (ferrite + austenite) range, resulted in a decrease of the volume fraction of retained austenite.It was also found that during annealing in Ac1s÷Ac1f temperature range, austenite is also formed from ferrite simultaneously. This could be the reason for the decrease the carbon content in the formed austenite and consequently the decrease in the volume fraction of retained austenite in the microstructure of the investigated steel, which was quenched after having reached temperatures higher than Ac1s + 30°C.

scholarly journals The Effect of Stepped Austempering on Phase Composition and Mechanical Properties of Nanostructured X37CrMoV5-1 Steel

2015 ◽  
Vol 60 (1) ◽  
pp. 517-521
Author(s):  
S. Marciniak ◽  
E. Skołek ◽  
W. Świątnicki
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Isothermal Annealing ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
High Volume ◽  
Thin Layers ◽  
Strength Parameters ◽  
One Step ◽  
Step Heat Treatment

AbstractThis paper presents the results of studies of X37CrMoV5-1 steel subjected to quenching processes with a one-step and a two-step isothermal annealing. The TEM observation revealed that steel after one-step treatment led is composed of carbide-free bainite with nanometric thickness of ferrite plates and of high volume fraction of retained austenite in form of thin layers or large blocks. In order to improve the strength parameters an attempt was made to reduce the austenite content by use of quenching with the two-step isothermal annealing. The temperature and time of each step were designed on the basis of dilatometric measurements. It was shown, that the two-step heat treatment led to increase of the bainitic ferrite content and resulted in improvement of steel's strength with no loss of steel ductility.

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