Plastic Localization Phenomena in a Mn-Alloyed Austenitic Steel

Abstract

A 0.5 wt pct C, 22 wt pct Mn austenitic steel, recently proposed for fabricating automotive body structures by cold sheet forming, exhibits plastic localizations (PLs) during uniaxial tensile tests, yet showing a favorable overall strength and ductility. No localization happens during biaxial Erichsen cupping tests. Full-thickness tensile and Erichsen specimens, cut from as-produced steel sheets, were polished and tested at different strain rates. During the tensile tests, the PL phenomena consist first of macroscopic deformation bands traveling along the tensile axis, and then of a series of successive stationary deformation bands, each adjacent to the preceding ones; both types of bands involve the full specimen width and yield a macroscopically observable surface relief. No comparable surface relief was observed during the standard Erichsen tests. Because the stress state is known to influence PL phenomena, reduced-width Erichsen tests were performed on polished sheet specimens, in order to explore the transition from biaxial to uniaxial loading; surface relief lines were observed on a 20-mm-wide specimen, but not on wider ones.

High-Cycle Fatigue Resistance of Si-Mo Ductile Cast Iron as Affected by Temperature and Strain Rate

“…In fact, such plastic instabilities generally occur in a well-defined range of temperature and strain rate and are caused by negative strain rate sensitivity. [24,25] The high-frequency, 10 million cycles fatigue strength is remarkably constant between room temperature and 673 K (400°C), and thereafter decreases, but not nearly as much as the yield stress and the ultimate tensile strength. In particular, the ratio of the (high-frequency) fatigue strength to the ultimate tensile strength, which is 0.39 at room temperature, increases to about 0.53 at 673 K (400°C), and eventually to 1.38 at 973 K (700°C).…”

Mechanical Properties and Tensile Fracture Mechanisms of Fe–Mn–(Al, Si) TRIP/TWIP Steels with Different Ferrite Volume Fractions

“…Figure 2b shows the XRD profiles of g, a 0 , and e phases after tension. The (101) diffraction peak of e phase (hcp structure) is also detected in Fe- (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)Mn-Al-Si samples. Apparently, the deformation-induced martensite transformation (DIMT) via g !…”

Comparison of Damage Evolution in Different Steels by Means of 3D X Ray Tomography

“…The second term 1 N dN de ð R À R 0 Þ gives the influence of the cavity nucleation on the average radius. N is the number of cavities by mm 3 and R 0 is the radius of cavity at nucleation. Figure 9 presents the evolution of the average diameter measure, thanks to 3D X ray tomography experiment compared to the above model.…”

“…For instance, the high manganese TWIP steels do not exhibit any necking and the fracture occurs during the uniform elongation, at least at room temperature as shown for example on the TWIP 940 by Chung et al [1,2] An other typical feature of the fracture of the TWIP steels is, whatever the stress state, the slant fracture surface. [3] However, the microscopical features that lead to fracture are still under debate. Only a few papers deal with the fracture of TWIP steels and particularly of Hadfield steels (i.e., with a Mn content between 12 and 14%).…”