Papers by Keyword: TRIP Steel

Abstract: The paper presents results of in-situ neutron diffraction experiments aimed on monitoring the phase evolution and load distribution in TRIP steel when subjected to tensile loading. Tensile deformation behaviour of TRIP steel with different initial microstructures showed that the applied tensile load is redistributed at the yield point and the harder retained austenite (Feγ) bears larger load then ferrite (Feα) matrix. After load partioning is finished, macroscopic yielding comes through simultaneous activity of the martensite transformation (in the austenite) and plastic deformation process in ferrite. The steel with higher volume fraction of retained austenite and less stronger ferrite appears to be a better TRIP steel having efficient structure for better plasticity purpose.

Abstract: Incremental Sheet Forming (ISF) is a flexible technology for forming customized productions in small batch, and has received wide attention, especially in the automobile manufacturing industry, where TRIP(Transformation Induced Plasticity) steel is widely used for its great ductility and high strength. But the springback of TRIP steel products is more serious than that of common steel ones, which induce the low dimensional accuracy and block the industrial application. This work would illustrate the experimental research on the dimensional accuracy of TRIP steel products in ISF. To make a reasonable accuracy evaluation, square cone-shaped samples of 1060Al and 08F steel were formed by ISF as the reference. By comparing the outline unconformity and the dimensional deviation, it comes to the conclusion that dimensional accuracy of TRIP steel sheet products is much lower than that of other materials.

Abstract: Current status of a dedicated neutron diffractometer (TAKUMI) for investigations of stresses and crystallographic structures in engineering components, that has been built at Materials and Life Science Facility of J-PARC, was introduced as well as the engineering studies done there. Several topics recently performed at TAKUMI were selected to be introduced; internal strains in an ITER central solenoid conductor sample, internal strains in a rebar embedded in an air-cured concrete, deformation behavior of TRIP steels at RT and tensile behavior of LPSO Mg­Zn­Y alloys. These topics and the relevant results showed that TAKUMI is a powerful neutron diffractometer for various engineering studies.

Abstract: TRIP (Transformation induced plasticity) steel has a good combination of high strength and high plasticity which depend on the micro phase transformation and staking fault development greatly. C atom was typical alloying agent of austenite and plays an important role in austenite behavior, especially for staking fault nucleation. As a micro materials behavior, molecular dynamics simulation was carried out to discuss the effect of C atom on the staking fault nucleation. From the simulation result we can find that carbon influence the staking fault nucleation greatly, with the increasing of the number of C atoms, strain for staking fault form decreased, system with 4 C atoms staking fault formed when strain was 7.5% and for system without C atoms there are no staking fault with local tension strain up to 10%. Under the same deformation, stacking fault distribution was uniform for the system with 1 carbon and become uneven with the increasing of the C atom.

Abstract: Grinding ball is grinding body of ore, cement, coal and other solid materials in the ball mill grinding and is one of the biggest consumption in wearable element of powder industry. In this paper, using the principle of transformation induced plasticity, reinforcement, toughening, according to the new design ideas, a kind of TRIP steel is designed in order to improve wear-resisting property of the grinding ball.

Abstract: Transformation induced plasticity steels (TRIP steel) is a kind of low – alloying high strength steel with good combination of strength and plasticity. But the macro mechanical properties depend on the microstructure greatly. For simulation, macro finite element can’t consider the microstructure development fully and micro molecular dynamics can’t be used in macro engineering widely, so to investigate the material behavior of trip steel a multi-scale simulation framework which combined macro finite element simulation and micro molecular dynamics together was presented in this paper. The transformation technology between macro and micro simulation by internal variable was considered and macro displacement of integral point as boundary condition of micro molecular dynamics was discussed.

Abstract: The microstructures of CR600TR steel were characterized using optical metallography, SEM, TEM and EBSD techniques, especially the transformation behavior of retained austenite and fracture mechanism of TRIP steel under stress-strain were studied in detail. It is discovered that there is marked selectivity for those retained austenite grains in their transition sequences: they are even dependent on the extension paths of stress-strain in steel and that curvatures of grain-boundaries which the retained austenite grains lie in.

Abstract: The method using variable blank holding force to control springback in drawing of TRIP sheet steel is discussed. Numerical simulations considering the variation of Youngs modulus of TRIP steels can improve springback simulation accuracy. Many experiments are use to test and the accuracy of the springback simulation for an U-channel part forming under variable blank holding force. The results shows that the strategy of variable blank holding force is an effective measure for the springback control in TRIP sheet metal forming processes and the dimensional accuracy of sheet metal parts can be increased by the optimization of variable blank holding forces

Abstract: The combined effect of Al and Nb additions on the static softening behavior of C-Mn steels was investigated. The compositions of the steels studied in this work are representative of the recently developed TRIP-assisted steels: a base composition of 0.2wt.%C, 2wt.%Mn, 50ppmN, three different Al levels, 0.03 (base steel), 1 and 2wt.%, and two Nb contents of 0.03 and 0.07wt.%. Double-hit torsion tests were performed at different deformation temperatures (925-1065oC) and pass-strains (=0.2 and 0.35). It was found that solute Al produced a significant retardation on the static softening kinetics, this effect being enhanced by the addition of Nb. Additionally, below 1000oC the addition of 2 wt.%Al promotes the γα phase transformation to occur concurrently with softening. For the Nb microalloyed steels strain induced precipitation also occurred, resulting in a complex interaction between softening, phase transformation and strain induced precipitation.

Abstract: Improved formability has been reported due to stress relaxation when the continuous forming cycle is interrupted with steps by adjusting the punch motion. The contribution of stress relaxation and its parameters on the ductility of materials has not been established so far. In the present work, the stress relaxation behavior of three materials, low carbon steel, DP and TRIP steels are studied. The influence of strain rate and strain on the ductility enhancement due to stress relaxation is analyzed. It is observed that stress relaxation improved the ductility of materials in all the cases and therefore can be used as a potential method to improve formability in sheet metal forming.