scholarly journals Transformation-Induced Ductility of Reverse Austenite Evolved by Low-Temperature Tempering of Martensite

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1343
Author(s):  
Pengju Du ◽  
Peng Chen ◽  
Devesh K. Misra ◽  
Di Wu ◽  
Hongliang Yi
Keyword(s):  
Uniform Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
High Yield ◽  
Interface Migration ◽  
Martensitic Matrix ◽  
Advanced High Strength Steels ◽  
Boundary Sliding ◽  
Quenching And Tempering ◽  
Martensite Matrix

A novel steel combining the “quenching and tempering (Q&T)” process was exploited that can achieve the enhancement of austenite by interface migration during tempering the martensitic matrix mixed with films of austenite. A high uniform elongation (12%) combined with high yield tensile strength (1500 MPa) was obtained, which showed distinct advantages over all the other advanced high strength steels under development for a lightweight car body. Furthermore, the effect of austenite on enhancement of ductility in “Q&T” steels with a martensite matrix was elucidated, which suggested that the ductility was promoted by enhancing boundary sliding and delaying work hardening of the martensitic matrix.

scholarly journals High Rate Characterization of Three DP980 Steels

2018 ◽  
Vol 183 ◽  
pp. 02060
Author(s):  
Amir Zhumagulov ◽  
Armin Abedini ◽  
Taamjeed Rahmaann ◽  
José Imbert ◽  
Clifford Butcher ◽  
...  
Keyword(s):  
Uniform Elongation ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
High Rate ◽  
Experimental Program ◽  
Static Tests ◽  
Advanced High Strength Steels ◽  
Energy Absorbing

Advanced high strength steels (AHSS) are used extensively in the automotive industry in the ongoing effort to reduce vehicle weight. Their increased strength allows for the reduction of sheet thickness, and thus a reduction in mass, while offering formability and cost advantages when compared to other metal alloys typically considered for lightweight applications. DP980 steels are AHSS being considered for structural energy absorbing components; however, there is a lack of published information on their high rate behaviour. This paper presents the results of an experimental program that characterized three production DP980 steels from three different manufacturers at strain rates of 0.001, 1, 10, 100 and 1,000 s-1. An electro-mechanical frame was used for the quasi-static tests, the 1, 10, and 100 s-1 tests were carried out using a fast hydraulic apparatus and the 1,000 s-1 experiments were carried out using a tensile split Hopkinson bar. The quasi-static hardening response at strains higher than the uniform elongation of about 7% was obtained by using a shear test, thus avoiding the use of inverse modelling techniques. The results indicate that the DP980 steels are moderately rate sensitive, with one of the materials showing higher sensitivity than the others. One of the materials exhibited a yield point phenomenon that appears to affect the behaviour of the material at 100 and 1,000 s-1, however, the reasons for this behaviour remain an open question. The data was fit to modified Johnson-Cook and Cowper-Symonds model to account for rate sensitivity. The results presented in this paper provide a tool for modelling the dynamic behaviour of DP980 steels.

Fatigue Performance of Laser Brazes in Advanced High Strength Steels

2010 ◽  
Vol 638-642 ◽  
pp. 3254-3259 ◽  
Author(s):  
M.H.E. Janssen ◽  
M.J.M. Hermans ◽  
M. Janssen ◽  
I.M. Richardson
Keyword(s):  
Mechanical Properties ◽  
Trip Steel ◽  
Uniform Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
Process Conditions ◽  
Trip Steels ◽  
Advanced High Strength Steels ◽  
Brazed Joints ◽  
Welding Processes

Advance high strength steels (AHSS), like dual phase (DP) and transformation induced plasticity (TRIP) steels, offer high strength and toughness combined with excellent uniform elongation. However, the higher alloying content of these steels limit their weldability and the thermal cycle of welding processes destroys the carefully designed microstructure. This will result in inferior mechanical properties of the joint. Therefore, joining processes with a low heat input, like brazing, are recommendable. Data regarding mechanical properties of joints in DP and TRIP steel is limited, especially for brazed joints. Results with respect to the fatigue lifetime of laser brazed butt joints are presented. In DP and TRIP steel, crack initiation takes place at the braze toe. In DP steel the crack propagates through the base metal. In TRIP steel, however, the crack may either follow the interface or may continue through the steel depending on the maximum stress level. The different failure mechanisms are explained on the basis of process conditions, the microstructure and the stress state.

Friction Coefficient Identification in Roll Forming Processes

2014 ◽  
Vol 611-612 ◽  
pp. 425-435 ◽  
Author(s):  
Lander Galdos ◽  
Unai Ulibarri ◽  
Imanol Gil ◽  
Rafael Ortubay ◽  
Eneko Sáenz de Argandoña
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Roll Forming ◽  
High Yield ◽  
High Yield Strength ◽  
Forming Process ◽  
Advanced High Strength Steels ◽  
High Production Rate ◽  
High Production ◽  
Roll Forming Process

Roll forming process is an interesting process for the production of complex profiles because of its high production rate, low investment and efficient use of material. Furthermore, and due to their high yield strength, this technology is suitable for the forming of Advanced High Strength Steels which are being increasingly introduced in the automobile sector.

Numerical modeling of stress-strain relationships for advanced high strength steels

2021 ◽  
Vol 182 ◽  
pp. 106687
Author(s):  
Yu Xia ◽  
Chu Ding ◽  
Zhanjie Li ◽  
Benjamin W. Schafer ◽  
Hannah B. Blum
Keyword(s):  
Numerical Modeling ◽  
High Strength Steels ◽  
High Strength ◽  
Stress Strain ◽  
Advanced High Strength Steels

scholarly journals Heat Treatment Design for a QP Steel: Effect of Partitioning Temperature

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1136
Author(s):  
Marcel Carpio ◽  
Jessica Calvo ◽  
Omar García ◽  
Juan Pablo Pedraza ◽  
José María Cabrera
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Quenching Temperature ◽  
Advanced High Strength Steels ◽  
New Family ◽  
Automotive Parts ◽  
Fresh Martensite ◽  
Industry Needs

Designing a new family of advanced high-strength steels (AHSSs) to develop automotive parts that cover early industry needs is the aim of many investigations. One of the candidates in the 3rd family of AHSS are the quenching and partitioning (QP) steels. These steels display an excellent relationship between strength and formability, making them able to fulfill the requirements of safety, while reducing automobile weight to enhance the performance during service. The main attribute of QP steels is the TRIP effect that retained austenite possesses, which allows a significant energy absorption during deformation. The present study is focused on evaluating some process parameters, especially the partitioning temperature, in the microstructures and mechanical properties attained during a QP process. An experimental steel (0.2C-3.5Mn-1.5Si (wt%)) was selected and heated according to the theoretical optimum quenching temperature. For this purpose, heat treatments in a quenching dilatometry and further microstructural and mechanical characterization were carried out by SEM, XRD, EBSD, and hardness and tensile tests, respectively. The samples showed a significant increment in the retained austenite at an increasing partitioning temperature, but with strong penalization on the final ductility due to the large amount of fresh martensite obtained as well.

Selection and use of coated advanced high-strength steels for automotive applications

2004 ◽  
Vol 101 (7-8) ◽  
pp. 551-558 ◽  
Author(s):  
R. Bode ◽  
M. Meurer ◽  
T. W. Schaumann ◽  
W. Warnecke
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Automotive Applications ◽  
Advanced High Strength Steels

Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test

2021 ◽  
pp. 030932472110212
Author(s):  
Mohammad Mehdi Kasaei ◽  
Marta C Oliveira
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Rate ◽  
Contact Pressure ◽  
Deformation Behaviour ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Deformation Mechanics ◽  
Nakajima Test

This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.

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