Fatigue Behavior of High Manganese TWIP Steels and of Low Alloy Q&P Steels for Car-Body Applications

2014 ◽  
Vol 783-786 ◽  
pp. 713-720
Author(s):  
Paolo Matteis ◽  
Giorgio Scavino ◽  
R. Sesana ◽  
F. D’Aiuto ◽  
Donato Firrao
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Austenitic Steels ◽  
Fracture Mechanisms ◽  
High Manganese ◽  
Cold Forming ◽  
Austenitic Structure ◽  
Plasticity Effect ◽  
Twip Steels

The automotive TWIP steels are high-Mn austenitic steels, with a relevant C content, which exhibit a promising combination of strength and toughness, arising from the ductile austenitic structure, which is strengthened by C, and from the TWIP (TWinning Induced Plasticity) effect. The microstructure of the low-alloy Q&P steels consists of martensite and austenite and is obtained by the Quenching and Partitioning (Q&P) heat treatment, which consists of: austenitizing; quenching to the Tqtemperature, comprised between Msand Mf; soaking at the Tppartitioning temperature (Tpbeing equal to or slightly higher than Tq) to allow carbon to diffuse from martensite to austenite; and quenching to room temperature. The fatigue behavior of these steels is examined both in the as-fabricated condition and after pre-straining and welding operations, which are representative of the cold forming and assembling operations performed to fabricate the car-bodies. Moreover, the microscopic fracture mechanisms are assessed by means of fractographic examinations.

The Study of Type Twin Annealing in High Mn Steel

2011 ◽  
Vol 148-149 ◽  
pp. 1085-1088
Author(s):  
Gholam Reza Razavi
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Room Temperature ◽  
Twip Steel ◽  
Manganese Steel ◽  
High Manganese ◽  
High Manganese Steel ◽  
Twip Steels ◽  
Mn Steel

TWIP steels are high manganese steel (Mn: 17% - 35%) which are used for shaping car bodies. The structure of this kind of steels remains austenite even in room temperature. Due to low SFE (Stacking Fault Energy) twinning of grains is governing reformation mechanism in this kind of steels which strengthen TWIP steel. Regarding heat treatment influences on mechanical properties of TWIP steels, in this paper we discuss twinning phenomenon resulting from this kind of treatment. For this, following casting and hot rolling processes, we anneal the steel at 1100°C and different time cycles and study its microstructure using light microscope. The results showed that with decreasing grain size the number of twin annealing added And four types of annealing twin in the microstructure, in the end they all become one twin and then turn into grain.

Effects of Al addition on deformation and fracture mechanisms in two high manganese TWIP steels

2011 ◽  
Vol 528 (6) ◽  
pp. 2922-2928 ◽  
Author(s):  
Kwang-Geun Chin ◽  
Chung-Yun Kang ◽  
Sang Yong Shin ◽  
Seokmin. Hong ◽  
Sunghak Lee ◽  
...  
Keyword(s):  
Fracture Mechanisms ◽  
High Manganese ◽  
Deformation And Fracture ◽  
Twip Steels ◽  
Al Addition

Simulation of Heat Assisted Forming of Commercial Aluminium Alloy AA5182

2011 ◽  
Vol 473 ◽  
pp. 675-682 ◽  
Author(s):  
Rajarajan Govindarajan ◽  
Martin Zubeil ◽  
Kathleen Siefert ◽  
Christophe Ageorges ◽  
Karl Roll
Keyword(s):  
Heat Treatment ◽  
Aluminium Alloy ◽  
Room Temperature ◽  
Heat Treating ◽  
Tensile Tests ◽  
Experimental Investigations ◽  
Body Parts ◽  
Cold Forming ◽  
Commercial Aluminium ◽  
Automotive Interior

To improve the formability of commercial aluminium alloy AA5182, a new heat assisted forming method is used. The process sequence of this method is; cold forming (pre-forming, 90 to 95% of final shape), heat treatment and cooling it down to room temperature and final cold forming. AA5182 is a non-heat treatable alloy and hence heat treating a strain hardened non-heat treatable aluminium alloy leads to lose in strength and gain in plastic recovery. Therefore by heat treating a preformed part and then following it up by further forming stages, it not only gains the lost strength back but also shows increased formability. This behavior is particularly useful in forming more complex automotive interior body parts. To accurately simulate this method, modeling the effect of heat treatment is important. Initial investigations on tensile tests showed that the degree of pre-forming in combination with heat treatment is directly proportional to plastic recovery. Which means, the more the pre-strain is the more the recovery becomes viable. Based on this, a new algorithm has been developed and implemented in LS-DYNA to capture the effect of heat treatment. Finally experimental investigations were carried out on a cross die deep drawn cup to validate the developed simulation model.

Fatigue Behavior of Extruded Mg-Al-Ca-Mn Alloy with T6 Treatment at Elevated Temperature

2014 ◽  
Vol 627 ◽  
pp. 417-420 ◽  
Author(s):  
Yukio Miyashita ◽  
Hugo Inzunza ◽  
Adrian Elizondo ◽  
Yoshiyuki Murayama ◽  
Yuichi Otsuka ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Property ◽  
Propagation Behavior ◽  
Replication Technique

Fatigue behavior of Mg-Al-Ca-Mn alloy with T6 treatment was studied at room temperature and 150°C by conduction rotating bending fatigue test. Fatigue strength at high temperature was lower than that at room temperature in the alloys with and without heat treatment. However, degradation of fatigue strength at high temperature in the T6 treated alloy was not significant compared to the as-extruded alloy. Fatigue crack initiation and propagation behavior was observed with replication technique by conducting interrupted fatigue test at room temperature and 150°C. Multiple cracking was significantly observed at 150°C in both as-received and T6 treated alloys. Change in grain size and randomization of crystal orientation due to the heat treatment could affect the fatigue property.

Intermediate Heat Treatment – A New Proceeding for Aluminum Alloys Using Forming Limit Diagrams

2011 ◽  
Vol 473 ◽  
pp. 428-435 ◽  
Author(s):  
Kathleen Siefert ◽  
Marion Merklein ◽  
Almut Töpperwien ◽  
Winfried Nester ◽  
Martin Grünbaum
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Strain Hardening ◽  
Room Temperature ◽  
Forming Limit ◽  
Cold Forming ◽  
Intermediate Heat Treatment ◽  
Heat Treated ◽  
Strain Paths

This paper presents a new procedure for a heat treatment embedded between two cold forming steps. A first cold forming step induces a defined strain hardening in the material. The following step is the heat treatment which takes place in a furnace at various temperatures and for certain durations. The application of such an intermediate heat treatment reduces the strain hardening of the material and enhances the elongation. This allows a higher degree of deformation in the second cold forming operation. The achievable properties of the aluminum alloy AlMg4.5Mn (AA5182) were discussed in detail. Further investigations using Nakajima test setup revealed an increased formability of the material. First the Nakajima samples were pre-strained along different linear strain paths to a predefined strain value. Afterwards the samples were heat treated without allowing the aluminum alloy to recrystallize. After cooling down the samples to room temperature, the tests are continued until the material’s fracture. As a result heat treatment dependent forming limit curves (FLC) are obtained. In comparison with a measured FLC at room temperature the support of the intermediate heat treatment on enhanced formability were shown. Furthermore the method is not restricted to AA5182 aluminum alloys.

Fatigue Behaviour of Carbide Precipitation Hardened Austenitic Steels

2015 ◽  
Vol 226 ◽  
pp. 69-74
Author(s):  
Kazimierz J. Ducki ◽  
Marek Cieśla ◽  
Grzegorz Junak ◽  
Lilianna Wojtynek
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Austenitic Steels ◽  
Cycle Fatigue ◽  
Softening Effect ◽  
Fatigue Durability ◽  
Increased Temperature

The paper presents the results of investigations of the microstructure and fatigue behaviour of two newly invented Cr-Ni and Cr-Ni-Mn austenitic steels of 13/13 and 12/8/8 type strengthened through carbide particle precipitation. The specimens of the investigated steels were subjected to tests after heat treatment, i.e. solution heat treatment (1200°C/0.5 h/water) and aged at a temperature of 700°C for 12 h, with cooling in air. The heat treated specimens were then subjected to low-cycle fatigue tests (LCF), carried out at room temperature and at an increased temperature of 600°C. Diagrams of fatigue characteristics of the investigated steels at room temperature as well as at elevated temperature have been worked up. It has been found that during low-cycle fatigue tests, at both temperatures, the investigated austenitic steels indicated a fatigue softening effect. The results of LCF at room temperature showed that the fatigue durability (Nt) of both austenitic steels is located in the range 0.8÷1.3×103 cycles. The results of low-cycle fatigue tests at an increased temperature 600°C indicated that the fatigue durability of the investigated steel was lower, and is located in the range Nt = 0.5÷0.6×103 cycles. It has been pointed out that the investigated austenitic steels are characterized by a stability of structure in conditions of cyclic fatigue.

Analysis of 1.4571 Chrome-Nickel Steel Properties after Cold Forming by Bending

2019 ◽  
Vol 952 ◽  
pp. 29-36
Author(s):  
Dana Stančeková ◽  
Mária Michalková ◽  
Milan Sapieta ◽  
Michal Šajgalík ◽  
Miroslav Janota
Keyword(s):  
Heat Treatment ◽  
Plastic Deformation ◽  
Deformation Mechanisms ◽  
Thermal Processes ◽  
Nickel Steel ◽  
Forming Force ◽  
Cold Forming ◽  
Austenitic Structure ◽  
Deformation Processes ◽  
Steel Properties

The paper deals with the problems of austenitic chrome-nickel steels and their behavior in plastic deformation processes. These steels cannot be hardened by thermal processes due to a stable austenitic structure, therefore the increase of strength is achieved only by cold forming. The deformation mechanisms of the slip or twinning are activated by the effect of the forming force in the steel. Mainly, there is formed deformation-induced martensite whose structure is different from the martensite created by the heat treatment. As the intensive hardening of austenitic chrome-nickel steels under the effect of plastic deformation is beneficial, it adversely affects the machining of these materials.

Evolution of Special Grain Boundaries in Austenitic Steels

2007 ◽  
Vol 537-538 ◽  
pp. 355-362 ◽  
Author(s):  
Z. Gaál ◽  
Péter János Szabó
Keyword(s):  
Stainless Steel ◽  
Room Temperature ◽  
Electron Back Scatter Diffraction ◽  
Austenitic Steels ◽  
Boundary Structure ◽  
Cold Forming ◽  
Grain Boundary Structure ◽  
Different Types ◽  
Temperature Electron ◽  
Cold Rolled

Three different types of austenitic stainless steel (SUS 304, SUS 304L and SUS 316) samples were cold formed in order to investigate the effect of cold forming on the grain boundary structure of the material. SUS 304L and SUS 316 samples were cold rolled, SUS 304 samples were tensile loaded in different manner at room temperature. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that the frequency of the special Σ3n type CSLboundaries was significantly decreased by increasing the deformation of the samples.

Fatigue Behavior of Magnesium Alloy AJ91 Studied by Amplitude Dependent Damping Measurements

2012 ◽  
Vol 184 ◽  
pp. 185-190 ◽  
Author(s):  
Werner Riehemann ◽  
Zuzanka Trojanová
Keyword(s):  
Heat Treatment ◽  
Magnesium Alloy ◽  
Resonant Frequency ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Quenching Temperature ◽  
Measured Strain ◽  
Number Of Cycles ◽  
Cast Condition

The amplitude dependent damping of two bending beam samples of magnesium alloy AJ91 (9 wt.% Al, 1 wt.% Sr) was measured at room temperature in as cast condition, after quenching from high temperatures into water of room temperature and after various bending cycles to fatigue. Some measurements were performed successively with about 33 Hz and 100 Hz resonant frequency. The measurements show typical dislocation damping in as cast condition, after heat treatment at temperatures lower than 420°C, and cycle numbers lower then 50.000. For higher quenching temperatures the damping increases over the whole measured strain range with increasing quenching temperature and number of cycles to fatigue. After quenching from temperatures higher than 478°C the crack damping becomes dominant. The effects of damping seem to increase with increasing frequency. In one sample damping of individual cracks could be identified in the amplitude dependent damping curves by their characteristic course very similar to the ones postulated in an earlier publication by a simple rheological model [4]. The extending of crack length leads to a shift of the damping to lower strains.

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