Modeling and Numerical Validation of Stress-Strain Curves of Maraging Steels, Grades 300 and 350 Under Hydrogen Embrittlement

Abstract

Maraging steels are ferrous alloys with Ni, Co, Mo, and Ti additions. These materials are a special class of ultra high mechanical strength steels with wide and special applications in strategic areas, which makes their knowledge very valuable. Computational advances allowed to analyze the behavior of these materials numerically, using the finite element method and developing mathematical models that can represent numerically its mechanical behavior. The present work has the objective of surveying the mechanical properties of maraging steels 300 and 350 by slow strain rate tensile (SSRT) tests, after the solution treatment at 1183K for 1h. Additionally, it was evaluated the hydrogen embrittlement in samples tested by SSRT under cathodic protection with a potential -1.2 VSCE in 3.5% NaCl solution.The study was complemented with detailed fractographic analysis. This work also presents the analysis of representative models by use of Hollomon, Swift, Voce and coupled Swift-Voce equations to describe the strain-hardening behavior. Compared to the others, the Voce's model was the one which best fitted the experimental results, with values of R 2 higher than 0.992. Through the variation of the chemical composition found in the different grades of maraging steels, this work contemplates the creation of a generalized Voce model based on the variation of the Ti content. The work concludes presenting the generalized Voce model proposed and a numerical analysis of the SSRT results with a good accuracy of the strain-hardening response.

Mechanical Properties of UNS S39274 Superduplex Stainless Steel Work Hardened and Solution Annealed

“…The Voce's law is an isotropic hardening model employed to characterize the elasto-plastic region of the tensile test results commonly applied for materials with little hardening and high 3, where σ o is the proportional limit and ε is the true plastic strain of the material. P 1 (stiffness coefficient), P 2 (strain hardening coefficient) and P 3 (strain hardening exponent) are other hardening parameters 9,21 . Comparing the results in Table 6, the Voce's law simulations of plastic bahavior had the best fitting precision, with R 2 (coefficient of determination) values ranging from 0.990 to 0.993, whereas Holllomon and Ludwik models presented R 2 values from 0.859 to 0.939 and from 0.841 to 0.986, respectively.…”

“…Where n is the number of values obtained in the tension tests and k is the number of specimens evaluated for each condition. For each specimen, the stress values (Y-axis) resulting from the rearranged strain points were linearly approximated based on their respective acquisition points 9 . Three mathematical models were tested to describe σ versus ε curves (10,11,12) :…”

A Review of Flow Characterization of Metallic Materials in the Cold Forming Temperature Range and Its Major Issues

“…However, it can be meaningful only when the flow curves are normal, i.e., monotonically increasing, such as those of cold forgeable carbon steels [4,41,42]. The conventional approaches of obtaining flow stress behaviors at high strain and room temperature cannot be applied to some ultra-high strength steels [43,44], stainless steels [8,45,46], special heat-treated steels [47], aluminum alloys [48,49], new materials [50,51], etc.…”