55
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
L. Lamberson et al. (eds.), Dynamic Behavior of Materials, Volume 1, Conference Proceedings of the Society
for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-59947-8_10
Chapter 10
Simulated Construction of FeMnAlC Alloy System Phase Diagram
and Study of Its Dynamic Characterization
Constantine (Costas) G. Fountzoulas
Abstract Austenitic steels are nonmagnetic stainless steels in annealed condition, although they can become slightly magnetic when cold worked, that contain 18% chromium, 8–10% nickel, and low levels of carbon (The characteristics of austenitic steel. https://www.thebalance.com/metal-profile-austenitic-stainless-2340126). Known for their formability and
resistance to corrosion, austenitic steels are the most widely used grade of stainless steel. They are not magnetic and not
reheatable. They can be cold worked to improve hardness, strength, and stress resistance. However, stainless steels with a
low nickel and high nitrogen content are classified as 200 series nitrogen which offers another possibility. Because nitrogen
is a gas, however, only limited amounts of nitrogen can be added before deleterious effects arise, including the formation of
nitrides and gas porosity that weaken the alloy (The characteristics of austenitic steel. https://www.thebalance.com/metalprofile-austenitic-stainless-2340126). The addition of manganese and copper, also austenite formers, combined with the
inclusion of nitrogen allow for greater amounts of the gas to be added. As a result, these two elements, are often used to
replace nickel in 200 series stainless steels (The characteristics of austenitic steel. https://www.thebalance.com/
metal-profile-austenitic-stainless-2340126).
Keywords FeMnAlC Alloys · Phase diagram · Dynamic characterization
10.1 Background
Alloys of the FeMnAlC system have been primarily developed as possible alternatives to stainless steels for structural applications in moderately aggressive environments [2]. Their densities vary from 6.5 to 7.2 g/cm
3
compared to 7.8 g/cm
3
of 4340
steel and tensile strengths from 200 to 600 MPa. Such alloys, when solution treated, are nonmagnetic and present an austenitic structure that can be modified by thermal treatments. In this way, different combinations of mechanical strength, fracture
toughness, and physical properties can be obtained, and components for aeronautical and chemical industries are currently
in use. Alloys of the FeMnAlC system have been also studied for reasons such as oxidation resistant applications, cryogenic
applications, and stainless steel substitutes. Figure 10.1a, b shows a photomicrograph and X-ray diffraction pattern of ferrite
austenite steel and selected area electron diffraction of austenitic steel, respectively [3]. In this way, different combinations
of mechanical strength, fracture toughness, and physical properties can be obtained, and components for aeronautical and
chemical industries are currently in use. Mechanical properties of Fe–20Mn–(10–14)Al–(0–1.8)C (mass%) quaternary and
Fe–20Mn–(10–14)Al–(0.75–1.8)C–5Cr (mass%) quinary alloys were investigated by hardness, cold-workability, and tensile
tests at room temperature [4]. The γ (FCC) alloys in both quaternary and quinary systems with a low density of less than
7.0 g/cm
3
showed an excellent ductility and their hardness and tensile strength increased with increasing Al and C contents.
The γ + α (BCC) duplex alloys also exhibited a high tensile strength by controlling the volume fraction. TEM observation
confirmed that high hardness and tensile strength of the alloys with high Al and C contents are caused by the precipitation of
nano-size κ-carbide with perovskite structure during cooling from the annealing temperature. Fe–20Mn–11Al–1.8C–5Cr
alloy with a density of 6.51 g/cm
3
showed a high specific strength of more than 180 MPa cm
3
/g with a good tensile elongation of 40%.
C. G. Fountzoulas (*)
CCDC Army Research Laboratory, WMRD, Aberdeen Proving Ground, MD, USA
e-mail: Constantine.fountzoulas.civ@mail.mil; jian.h.yu.civ@mail.mil
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
L. Lamberson et al. (eds.), Dynamic Behavior of Materials, Volume 1, Conference Proceedings of the Society
for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-59947-8_10
Chapter 10
Simulated Construction of FeMnAlC Alloy System Phase Diagram
and Study of Its Dynamic Characterization
Constantine (Costas) G. Fountzoulas
Abstract Austenitic steels are nonmagnetic stainless steels in annealed condition, although they can become slightly magnetic when cold worked, that contain 18% chromium, 8–10% nickel, and low levels of carbon (The characteristics of austenitic steel. https://www.thebalance.com/metal-profile-austenitic-stainless-2340126). Known for their formability and
resistance to corrosion, austenitic steels are the most widely used grade of stainless steel. They are not magnetic and not
reheatable. They can be cold worked to improve hardness, strength, and stress resistance. However, stainless steels with a
low nickel and high nitrogen content are classified as 200 series nitrogen which offers another possibility. Because nitrogen
is a gas, however, only limited amounts of nitrogen can be added before deleterious effects arise, including the formation of
nitrides and gas porosity that weaken the alloy (The characteristics of austenitic steel. https://www.thebalance.com/metalprofile-austenitic-stainless-2340126). The addition of manganese and copper, also austenite formers, combined with the
inclusion of nitrogen allow for greater amounts of the gas to be added. As a result, these two elements, are often used to
replace nickel in 200 series stainless steels (The characteristics of austenitic steel. https://www.thebalance.com/
metal-profile-austenitic-stainless-2340126).
Keywords FeMnAlC Alloys · Phase diagram · Dynamic characterization
10.1 Background
Alloys of the FeMnAlC system have been primarily developed as possible alternatives to stainless steels for structural applications in moderately aggressive environments [2]. Their densities vary from 6.5 to 7.2 g/cm
3
compared to 7.8 g/cm
3
of 4340
steel and tensile strengths from 200 to 600 MPa. Such alloys, when solution treated, are nonmagnetic and present an austenitic structure that can be modified by thermal treatments. In this way, different combinations of mechanical strength, fracture
toughness, and physical properties can be obtained, and components for aeronautical and chemical industries are currently
in use. Alloys of the FeMnAlC system have been also studied for reasons such as oxidation resistant applications, cryogenic
applications, and stainless steel substitutes. Figure 10.1a, b shows a photomicrograph and X-ray diffraction pattern of ferrite
austenite steel and selected area electron diffraction of austenitic steel, respectively [3]. In this way, different combinations
of mechanical strength, fracture toughness, and physical properties can be obtained, and components for aeronautical and
chemical industries are currently in use. Mechanical properties of Fe–20Mn–(10–14)Al–(0–1.8)C (mass%) quaternary and
Fe–20Mn–(10–14)Al–(0.75–1.8)C–5Cr (mass%) quinary alloys were investigated by hardness, cold-workability, and tensile
tests at room temperature [4]. The γ (FCC) alloys in both quaternary and quinary systems with a low density of less than
7.0 g/cm
3
showed an excellent ductility and their hardness and tensile strength increased with increasing Al and C contents.
The γ + α (BCC) duplex alloys also exhibited a high tensile strength by controlling the volume fraction. TEM observation
confirmed that high hardness and tensile strength of the alloys with high Al and C contents are caused by the precipitation of
nano-size κ-carbide with perovskite structure during cooling from the annealing temperature. Fe–20Mn–11Al–1.8C–5Cr
alloy with a density of 6.51 g/cm
3
showed a high specific strength of more than 180 MPa cm
3
/g with a good tensile elongation of 40%.
C. G. Fountzoulas (*)
CCDC Army Research Laboratory, WMRD, Aberdeen Proving Ground, MD, USA
e-mail: Constantine.fountzoulas.civ@mail.mil; jian.h.yu.civ@mail.mil