Microstructure, strain-rate sensitivity, work hardening, and fracture behavior of laser additive manufactured austenitic and martensitic stainless steel structures

Khodabakhshi, F.; Farshidianfar, M.H.; Gerlich, A.P.; Nosko, Martin; Trembošová, Veronika; Khajepour, Amir

doi:10.1016/j.msea.2019.04.065

Cited by 75 publications

(34 citation statements)

References 41 publications

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“…The values of m for the as‐received disk are estimated as ≈0.041 (center) and ≈0.040 (edge), which are of one order higher than 0.0061 obtained for coarse‐grained 316L SS and other typical coarse‐grained FCC metals, e.g., ≈0.004 for high‐purity Cu, ≈0.0028 for pure Ni, and ≈0.004 for Al 99.5 . However, these values are consistent with the m values for AM 316L SS as explained by Li et al, ranging from 0.02 to 0.03, when measured by tensile tests at different strain rates and strain rate jump tests.…”

Section: Discussionsupporting

confidence: 85%

“…[8,42,43,62] Therefore, the as-received SLM-fabricated 316L SS in this study can be considered to possess reasonably high plasticity characteristics, i.e., superior capability to sustain plastic deformation without fracture as indicated by the higher m value (%0.041) compared with its CM coarse-grain counterparts (e.g., %0.0061). [70] Even though the values of m slightly decrease at the early stages of HPT, these values remain consistent with increasing number of revolutions, indicating that a good level of plasticity is maintained along with the significant hardening obtained via HPT processing. Furthermore, based on the evolution of V * p values and the microstructural observations in this study, it can be concluded that the predominant deformation mechanism in the as-received AM 316L SS is attributed to the numerous submicron-and nanoscale microstructural features, rather than GB-related activities, although the low value of V * p is often related to GB-regulated plasticity.…”

Section: Discussionmentioning

confidence: 74%

“…For nanoindentation, the Tabor empirical relationship of σ f ¼ H=C is used to estimate σ f , in which H is the nanohardness estimated from the P-h curves based on the Oliver-Pharr method, [58] and the value of C is taken as 3 for fully plastic deformation at a constant strain rateε. [67,69] Thus, the values of m are estimated from the gradient of a double logarithmic plot of H/3 versusε and shown as inset in Figure 9, whereas the evolution of The values of m for the as-received disk are estimated as %0.041 (center) and %0.040 (edge), which are of one order higher than 0.0061 obtained for coarse-grained 316L SS [70] and other typical coarse-grained FCC metals, e.g., %0.004 for high-purity Cu, [71] %0.0028 for pure Ni, [72] and %0.004 for Al 99.5. [73] However, these values are consistent with the m values for AM 316L SS as explained by Li et al, [74] ranging from 0.02 to 0.03, when measured by tensile tests at different strain rates and strain rate jump tests.…”

Section: Discussionmentioning

confidence: 96%

“…Thus, there could be a change in the plastic deformation mechanism as a result of microstructural transition from the micro-to nanoscale due to HPT torsional straining. Therefore, the strain rate-dependent plastic deformation mechanism can be assessed by estimating the activation volume, V * p , based on the following relationship [50,70]…”

Section: Discussionmentioning

confidence: 99%

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Micromechanical Response of Additively Manufactured 316L Stainless Steel Processed by High‐Pressure Torsion

et al. 2020

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Numerous studies have reported attractive properties in ultrafinegrained (UFG) and nanograined (NG) metals and alloys compared with their coarse-grained (CG) counterparts, including significantly higher yields and tensile strengths, [1-3] enhanced wear and corrosion resistance, [4-6] and superplasticity at room temperature (RT). [7,8] It is now accepted that UFG and NG materials are defined as those having grain sizes in the range of 0.1-1 μm and <100 nm, respectively. Such remarkable properties are largely attributed to grain refinement and the generation of large amounts of dislocations in these grain scales, highlighting the benefit of fine grain microstructure. [9,10] To date, severe plastic deformation (SPD) processing has emerged as one of the most popular techniques that can produce bulk metals with UFG and NG microstructures, including equal-channel angular pressing (ECAP), high-pressure torsion (HPT), and accumulative roll bonding (ARB). From these techniques, HPT has been shown as the most effective method to produce true NG structures with large amounts of highangle grain boundaries (GBs) via the application of concurrent compressive force and torsional straining on HPT-processed samples. [11] In contrast, additive manufacturing (AM) has now been utilized to fabricate metallic components for niche engineering applications, e.g., automotive, biomedical, and aerospace, due to its attractive features of design flexibility, time and cost savings, and minimal material waste. [12] Selective laser melting (SLM) is one of the most widely used AM methods in the laser powder bed fusion (LPBF) category. As its name implies, SLM uses laser as the heat source to selectively consolidate layers of the powder bed into a complete 3D structure according to the initial computer-aided design (CAD) data. To date, a wide range of alloys have been used to fabricate metallic components using SLM, including 316L stainless steel (316L SS), Inconel 718 (IN 718), AlSi 10 Mg, and Ti6Al4V. [13,14] So far, research on metal AM has focused on optimizing processing parameters to achieve the highest densification levels with minimal porosity or defect contents. [15-28] To minimize

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Micromechanical Response of Additively Manufactured 316L Stainless Steel Processed by High‐Pressure Torsion

et al. 2020

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“…The area under the stress–strain curve could be defined as the fracture toughness by combining the strength and ductility [27]. The areas under the engineering stress–strain curves in Figure 1 were calculated and normalized by the value of the area at a 10 −4 s −1 strain rate.…”

Section: Resultsmentioning

confidence: 99%

A New Explanation for the Effect of Dynamic Strain Aging on Negative Strain Rate Sensitivity in Fe–30Mn–9Al–1C Steel

Xing

Hou

et al. 2019

Materials

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In this study, the evolution of the mechanical properties of Fe–30Mn–9Al–1C steel has been determined in tensile tests at strain rates of 10−4 to 102 s−1. The results show that the strain rate sensitivity becomes a negative value when the strain rate exceeds 100 s−1 and this abnormal evolution is attributed to the occurrence of dynamic strain aging. Due to the presence of intergranular κ-carbides, the fracture modes of steel include ductile fracture and intergranular fracture. The values of dislocation arrangement parameter M were obtained using a modified Williamson–Hall plot. It has been found that once the strain rate sensitivity becomes negative, the interaction of dislocations in the steel is weakened and the free movement of dislocation is enhanced. Adiabatic heating promotes the dynamic recovery of steel at a high strain rate.

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Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser‐Based Powder Bed Fusion

Taghipour

Mazaheri

McDavid³

et al. 2022

Adv Eng Mater

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The microstructure–properties relations and strengthening mechanisms of additively manufactured 316L stainless steel are comprehensively investigated in this work. The orientation dependency and the strain hardening are studied by tensile testing of as‐built specimens fabricated by laser‐based powder bed fusion (LPBF) in different directions. The results are compared with those obtained for wrought material. The microstructure of the wrought and the LPBF materials are also comprehensively investigated. Equiaxed grains with random orientation and relatively uniform size (≈30 μm) are observed in the wrought material, where the LPBF samples show columnar grains inside as well as fine equiaxed grains in the bottom of the molten pool. A bimodal grain size distribution, higher values of geometrically necessary dislocations density (≈25–32%), and lower fractions of high‐angle grain boundaries (≈24–28%) are observed in LPBF 316L. A significant yield strength and considerable ultimate strength improvement without remarkable elongation decrease are obtained for the LPBF tensile specimens, resulting in a high strength‐elongation balance (up to 26 122 MPa%). Two‐stage strain hardening is depicted in both wrought and LPBF samples. This is successfully predicted with two‐stage Hollomon analysis. However, the LPBF samples illustrate lower strain hardening exponents in comparison with the wrought ones.

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Microstructure, strain-rate sensitivity, work hardening, and fracture behavior of laser additive manufactured austenitic and martensitic stainless steel structures

Cited by 75 publications

References 41 publications

Micromechanical Response of Additively Manufactured 316L Stainless Steel Processed by High‐Pressure Torsion

Micromechanical Response of Additively Manufactured 316L Stainless Steel Processed by High‐Pressure Torsion

A New Explanation for the Effect of Dynamic Strain Aging on Negative Strain Rate Sensitivity in Fe–30Mn–9Al–1C Steel

Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser‐Based Powder Bed Fusion

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