Critical Assessment 16: Anisotropy in metals

Hutchinson, Bevis

doi:10.1179/1743284715y.0000000118

Cited by 63 publications

(50 citation statements)

References 45 publications

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“…∆R, calculated using Equation 1, represents an overall measure of the variation of R-value in the Y-Z build plane (planar anisotropy) where for an isotropic material: ∆R = 0. For AM materials, non-zero values of ∆R could be an indicator of preferred texture / alignment of the micro-structure due to the laser scanning pattern (especially in the distribution of second phases such as inclusions) / the presence of residual stresses [58]. The contour plot highlights that the range of ∆R variation is low across all treatments (<0.25 at 1.5% axial strain).…”

Section: R Valuementioning

confidence: 99%

Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments

Mooney

Kourousis

Raghavendra

2019

Additive Manufacturing

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This experimental study investigates the combined effect of the three primary Additive Manufacturing (AM) build orientations (0 • , 45 • , and 90 •) and an extensive array of heat treatment plans on the plastic anisotropy of maraging steel 300 (MS1) fabricated on the EOSINT M280 Direct Metal Laser Sintering (DMLS) system. The alloy's microstructure, hardness, tensile properties and plastic strain behaviour have been examined for various strengthening heattreatment plans to assess the influence of the time and temperature combinations on plastic anisotropy and mechanical properties (e.g. strength, ductility). A comprehensive visual representation of the material's overall mechanical properties, for all three AM build orientations, against the various heat treatment plans is offered through time-temperature contour maps. Considerable plastic anisotropy has been confirmed in the as-built condition, which can be reduced by aging heat-treatment, as verified in this study. However, it has identified that a degree of transverse strain anisotropy is likely to remain due to the AM alloy's fabrication history, a finding that has not been previously reported in the literature. Moreover, the heat treatment plan (6h at 490 • C) recommended by the DMLS system manufacturer has been found not to be the optimal in terms of achieving high strength, hardness, ductility and low anisotropy for the MS1 material. With the use of the comprehensive experimental data collected and analysed in this study, and presented in the constructed contour maps, the alloy's heat treatment parameters (time, temperature) can be tailored to meet the desired strength/ductility/anisotropy design requirements, either for research or part production purposes.

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Section: R Valuementioning

confidence: 99%

Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments

Mooney

Kourousis

Raghavendra

2019

Additive Manufacturing

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“…Arrow 4 points to precipitates assumed to form only when the material is kept above a critical temperature for an extended period of time [31]. The precipitates observed in the microstructure are likely contributing to the anisotropy, as reported by several authors [9,21,22], where the precipitates are dispersed along elongated grain boundaries and block the movement of dislocations within the crystal structure.…”

Section: Microstructure Investigationmentioning

confidence: 80%

“…There are two main sources of anisotropy: preferred crystallographic orientation and alignment in the microstructure of secondary phases and inclusions [21]. The latter is typically the main contributor to plastic anisotropy, while the former is often observed in elastically anisotropic materials.…”

Section: Introductionmentioning

confidence: 99%

“…The latter is typically the main contributor to plastic anisotropy, while the former is often observed in elastically anisotropic materials. The PBF-LB/M is known to bring on both sources of anisotropy in a range of materials [9,11,13,[21][22][23]. In metals with cubic crystal structure, the plastic anisotropy resulting from preferred crystallographic orientation is limited because of numerous slip planes that can be activated in different orientations.…”

Section: Introductionmentioning

confidence: 99%

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An investigation of the anisotropic properties of heat-treated maraging steel grade 300 processed by laser powder bed fusion

Hovig

Azar

Solberg

et al. 2021

Int J Adv Manuf Technol

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In order to explore the possibilities enabled by laser beam powder bed fusion of metals (PBF-LB/M), reliable material models are necessary to optimize designs with respect to weight and stiffness. Due to the unique processing conditions in PBF-LB/M, materials often develop a dominating microstructure that leads to anisotropic mechanical properties, and thus isotropic material models fail to account for the orientation-dependent mechanical properties. To investigate the anisotropy of 18Ni300 maraging steel, tensile specimens were built in seven different orientations. The specimens were heat treated at two different conditions and tested for their tensile properties using digital image correlation (DIC) technique. The microstructure and fracture surfaces are investigated with scanning electron microscope and electron backscatter diffraction. The tensile properties are typical for the material, with a yield strength in the range of 1850 MPa to 1950 MPa, and ultimate tensile strength in the range of 1900 MPa to 2000 MPa. The elastic modulus is 180 GPa, and the elongation at fracture is in the range of 2–6% for all specimens. The strain fields analysed with DIC reveals anisotropic straining in both the elastic and plastic parts of the flow curve for both direct ageing and solution treatment plus ageing specimens. In the former condition, the elastic anisotropy is dictated by the fraction of melt pool boundaries on the transverse surfaces of the specimens. When the material is solution treated prior to ageing, the melt pool boundary effect was supressed.

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“…The development of textures in worked metals was surveyed by Hutchinson in 2015 [ 29 ] who presents an interesting and wide-ranging review of the possible causes of anisotropy in metals. However, interestingly, and perhaps predictably, he concludes that a better understanding would be a suitable area for further investigation.…”

Section: Texturesmentioning

confidence: 99%

A Personal View of Microstructure and Properties of Al Alloys

Campbell

2021

Materials

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This paper presents a personal view by the author of the role of bifilms in Al alloys. The mantra ‘microstructure determines properties’ is widely accepted as a truism, but is here critically assessed and found wanting. The case is made that bifilms from the casting process, while often invisible in the microstructure, are usually at least as important, if not of far greater importance, because they are often present as a dense population of cracks throughout the metal. The bifilm population controls the morphology of many features of cast and wrought structures. For cast alloys, bifilm control of pore morphology and Si morphology in Al–Si alloys is discussed, as is dendrite arm spacing (DAS). The tensile property benefits of grain refinement are seen to be mainly bifilm controlled. The properties ductility and fatigue appear to be especially dominated by bifilm content, as are invasive corrosion processes such as pitting, intergranular corrosion, hydrogen blistering and cracking. Bifilm control is proposed as a new concept permitting the improvement and control of metallurgical properties.

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Critical Assessment 16: Anisotropy in metals

Abstract: Sources of anisotropy in metals are discusssed as well as ways of interpreting and modelling this behaviour. A number of case studies are presented relating to mechanical and magnetic properties.

Cited by 63 publications

References 45 publications

Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments

Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments

An investigation of the anisotropic properties of heat-treated maraging steel grade 300 processed by laser powder bed fusion

A Personal View of Microstructure and Properties of Al Alloys

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