Hot-Rolled TRIP Steels Based on Dynamic Transformation of Undercooled Austenite

2010 ◽  
Vol 654-656 ◽  
pp. 250-253 ◽  
Author(s):  
Wang Yue Yang ◽  
Long Fei Li ◽  
Yun Yang Yin ◽  
Zu Qing Sun ◽  
Xi Tao Wang
Keyword(s):  
Volume Fraction ◽  
High Volume ◽  
Test Machine ◽  
Compression Tests ◽  
Controlled Cooling ◽  
Thermomechanical Process ◽  
Trip Steels ◽  
Dynamic Transformation ◽  
Hot Rolled ◽  
Undercooled Austenite

A novel thermomechanical process to manufacture hot-rolled transformation-induced plasticity (TRIP) steels was developed based on dynamic transformation of undercooled austenite (DTUA). Between DTUA and the isothermal bainitic treatment, only one-step controlled-cooling was required. The microstructure evolution of hot-rolled C-Mn-Si and C-Mn-Al-Si TRIP steels based on DTUA was investigated by hot uniaxial compression tests using a Gleeble1500 simulation test machine. The results indicated that during DTUA, the kinetics of ferrite formation was fast, the volume fraction of ferrite formed was determined by applied strain. In comparison with the process based on static transformation of austenite, a more uniform multiphase microstructure with fine ferrite grains was formed, the bainite packets were small and had relatively random orientations, the retained austenite distributed uniformly and had relatively high volume fraction. Hot-rolled TRIP steels based on DTUA demonstrated better mechanical properties, especially for C-Mn-Al-Si TRIP steel.

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..

Mechanical Properties of Hypereutectoid Steel with Microduplex (α+θ) Structure Formed by Hot Deformation of Undercooled Austenite

2010 ◽  
Vol 654-656 ◽  
pp. 246-249
Author(s):  
Long Fei Li ◽  
Wei Chen ◽  
Wang Yue Yang ◽  
Zu Qing Sun
Keyword(s):  
Mechanical Properties ◽  
Hot Deformation ◽  
Ferrite Matrix ◽  
Subsequent Annealing ◽  
Test Machine ◽  
Compression Tests ◽  
Simulation Test ◽  
Hypereutectoid Steel ◽  
Lamellar Pearlite ◽  
Undercooled Austenite

Microstructure evolution and mechanical properties of hypereutectoid steel with the microduplex (α+θ) structures formed by hot deformation of undercooled austenite were investigated by hot uniaxial compression tests in a Gleeble-1500 simulation test machine, and the effects of subsequent annealing and the addition of Al were analyzed. The results indicated that at the beginning of hot deformation of undercooled austenite the formation of proeutectoid cementite was retrained and only lamellar pearlite was produced. With further strain, dynamic spheroidization of pearlite took place, leading to the formation of microduplex (α+θ) structure consisting of ultrafine ferrite matrix and dispersed cementite particles. In comparison with the normal microstructure consisting of lamellar pearlite and proeutectoid cementite, the microduplex (α+θ) structure presented higher strengths with similar ductility. Subsequent annealing could make the microduplex (α+θ) structure more uniform, which demonstrated better balance between strength and ductility. The addition of Al is disadvantageous to the formation of microduplex (α+θ) structure, but can result in the further refinement. With the addition of Al, the strength of microduplex (α+θ) structure was improved and the ductility was not deteriorated markedly.

Ultra Fine-Grained 6wt% Manganese TRIP Steel

2010 ◽  
Vol 654-656 ◽  
pp. 286-289 ◽  
Author(s):  
Sea Woong Lee ◽  
Kyoo Young Lee ◽  
Bruno C. De Cooman
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Intercritical Annealing ◽  
High Volume ◽  
Magnetic Saturation ◽  
Trip Steels ◽  
Fine Grained ◽  
Annealing Temperatures

Ultra-fine grained TRIP steels (UFG-TRIP) containing 6wt%Mn were produced by intercritical annealing. An ultra-fine grained microstructure with a grain size less than 1μm was obtained. The formation mechanism of the high volume fraction of retained austenite was investigated by dilatometry, XRD and magnetic saturation. The fraction of retained austenite was strongly dependent on the annealing temperature. The tensile properties were also found to be strongly influenced by the annealing temperature with poorer mechanical properties being observed at higher annealing temperatures. It was found that the stabilization of the retained austenite was both a composition and size-effect, made possible by the grain refinement due to the reversely transformed martensite.

Research on Intercritical Rolling of 0.2C-1.5Si-1.5Mn TRIP Steels by Thermo-Mechanical Simulation

2005 ◽  
Vol 297-300 ◽  
pp. 1223-1228
Author(s):  
Zuo Cheng Wang ◽  
Sung Joon Kim ◽  
Chang Gil Lee ◽  
Tae Ho Lee
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Intercritical Annealing ◽  
Rolling Process ◽  
Isothermal Treatment ◽  
Trip Steels ◽  
Mechanical Simulation ◽  
Size Refinement ◽  
Multi Phase ◽  
Hot Rolled

In order to simplify the production routine and to save cost of hot-rolled TRIP steels, the intercritical rolling process was investigated using thermo-mechanical simulation technology. Both 0.2C-1.5Mn-1.5Si and 0.2C-1.5Mn-1.5Si-0.5Cu TRIP steels were chosen so as to study the effect of 0.5 pct Cu addition on microstructure and retained austenite volume fraction of 0.2C-1.5Mn-1.5Si TRIP steel. It is found that grain size refinement happened during intercritical deformation, and multi-phase microstructure could be achieved after isothermal treatment, so intercritical annealing can be eliminated to avoid grain size coarse and to keep the refine grain size in intercritical-deformed TRIP steels.

Hot-die Forging of a β-stabilized γ-TiAl Based Alloy

2008 ◽  
Vol 1128 ◽  
Author(s):  
Wilfried Wallgram ◽  
Helmut Clemens ◽  
Sascha Kremmer ◽  
Andreas Otto ◽  
Volker Güther
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Small Deformation ◽  
High Volume ◽  
Compression Tests ◽  
Tial Alloys ◽  
Β Phase ◽  
Heat Treated ◽  
Hot Die Forging

AbstractBecause of the small “deformation window” hot-working of γ-TiAl alloys is a complex and difficult task and, therefore, isothermal forming processes are favoured. In order to increase the deformation window a novel Nb and Mo containing γ-TiAl based alloy (TNM™ alloy) was developed. Due to a high volume fraction of β-phase at elevated temperatures the alloy can be hot-die forged under near conventional conditions, which means that conventional forging equipment with minor and inexpensive modifications can be used. With subsequent heattreatments balanced mechanical properties can be achieved. This paper summarizes our progress in establishing a “near conventional” forging route for the fabrication of γ-TiAl components. The results of lab scale compression tests and forging trials on an industrial scale are included. In addition, the mechanical properties of forged and heat-treated TNM™ material are presented.

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.

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