A strategy for synthetic microstructure generation and crystal plasticity parameter calibration of fine-grain-structured dual-phase steel

Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high-strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈1017– ≈ 1018 cm−3. The relationship between trapping characteristics and HE susceptibility of MS-AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro-fracture (HAM).

Hydrogen Trapping in Some Automotive Martensitic Advanced High‐Strength Steels

In this study, two different dual phase steel grades DP980 and DP600, and IFHS steel sheets were laser welded by a 2-kW fiber laser. The weld quality of these three different LWBs was assessed with the help of microstructure, micro-hardness and transverse tensile tests. Tensile testing of longitudinal and miniature samples was performed to evaluate the mechanical properties of the weld zone. Formability of parent materials and LWBs were assessed in bi-axial stretch forming condition by Erichsen cupping test. To validate the weld zone properties, 3-D finite element models of Erichsen cupping test of LWBs was developed, and the failures in the deformed cups were predicted using two theoretical forming limit diagrams. It was observed that hardness of the fusion zone and HAZ in laser welded DP600 and IFHS steels was more compared to the respective parent metal. However, 29% reduction in hardness was observed at the outer HAZ of DP980 steel weldments due to tempering of martensite. Reduction of formability was observed for all the LWBs with two distinct failure patterns, and the maximum reduction in formability was observed in the case of DP980 LWBs. The presence of the soft zone is detrimental in forming of welded DP steels.

Investigations Into the Influence of Weld Zone on Formability of Fiber Laser-Welded Advanced High Strength Steel

The bipolar plate (BP) is one of the main drivers of the polymer electrolyte membrane fuel cell (PEMFC) stack cost, and must also perform some critical functions simultaneously within the stack to ...

Manufacturing methods for metallic bipolar plates for polymer electrolyte membrane fuel cell

Hydrogen embrittlement of an automotive 1700 MPa martensitic advanced high-strength steel

High strength steels are commonly used in the automotive industry to reduce mass and improve structural performance. This chapter discusses the history of steel in the manufacture of automobiles, the types of steels currently being used and the new advances in the types of steels that can be used for lightweighting automotive structures. The chapter also reviews the manufacturing and forming aspects of these steels along with some design considerations for the selection of these materials.

C.D. Horvath

Papers

Advanced steels for lightweight automotive structures