The effect of stress, temperature and loading direction on the creep behaviour of Ni-base single crystal superalloy miniature tensile specimens

Wollgramm, P.; Bürger, David; Parsa, Alireza B.; Neuking, K.; Eggeler, Gunther

doi:10.1080/09603409.2016.1186414

Cited by 77 publications

(26 citation statements)

References 68 publications

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“…Miniature tensile creep specimens [20] with the longitudinal axis parallel to the buildup direction, i.e., h100i direction, have been machined out of the reference cast material ERBO/1C and as-built/HT SX SEBM CMSX-4 Ò . The creep specimens with dog bone geometry have a measurement length of 9 mm and a thickness of 2 mm.…”

Section: Creep Testingmentioning

confidence: 99%

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Körner

Ramsperger

Meid

et al. 2018

Metall Mater Trans A

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133

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Currently, additive manufacturing (AM) experiences significant attention in nearly all industrial sectors. AM is already well established in fields such as medicine or spare part production. Nevertheless, processing of high-performance nickel-based superalloys and especially single crystalline alloys such as CMSX-4 Ò is challenging due to the difficulty of intense crack formation. Selective electron beam melting (SEBM) takes place at high process temperatures (~1000°C) and under vacuum conditions. Current work has demonstrated processing of CMSX-4 Ò without crack formation. In addition, by using appropriate AM scan strategies, even single crystals (SX SEBM CMSX-4 Ò ) develop directly from the powder bed. In this contribution, we investigate the mechanical properties of SX SEBM CMSX-4 Ò prepared by SEBM in the as-built condition and after heat treatment. The focus is on hardness, strength, low cycle fatigue, and creep properties. These properties are compared with conventional cast and heat-treated material.

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Section: Creep Testingmentioning

confidence: 99%

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Körner

Ramsperger

Meid

et al. 2018

Metall Mater Trans A

Self Cite

133

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“…The SX material was first mounted onto a goniometer and oriented into a specific crystallographic direction using a Laue system from Multiwire Laboratories (Lansing, NY, USA), equipped with an electronic position control unit and a sensitive real-time back reflection camera of type MWL120. The goniometer with the oriented specimen was subsequently fitted into an electro discharge machine (EDM) of type Charmilles Robofil 240 (Schorndorf, Germany), where the specimen was spark erosion machined as described in [15]. Figure 1 shows a photograph of the specimen together with a drawing which illustrates dimensions (shear width L = 2 mm, height H = 8 mm, and depth D = 3 mm) and crystallographic directions.…”

Section: Materials and Shear Creep Testingmentioning

confidence: 99%

How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

et al. 2020

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The present work investigates γ-channel dislocation reactions, which govern low-temperature (T = 750 °C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered γ’-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems [ 01 1 ¯ ] ( 111 ) and [ 11 2 ¯ ] ( 111 ) . These two shear systems share the same glide plane but differ in loading direction. The [ 11 2 ¯ ] ( 111 ) shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the [ 01 1 ¯ ] ( 111 ) shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.

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“…The results presented in Figures 10 and 11 provide mechanical and microstructural proof for the importance of h112i cutting of the c¢-phase and contribute to a better understanding of low-temperature and high-stress creep of single crystal Ni-base superalloys. [58][59][60] Further TEM studies are required to confirm these observations by investigating larger TEM foil regions and by analyzing the dislocation substructures in detail.…”

Section: B Anisotropic Creep Stress Calculationsmentioning

confidence: 99%

“…Gao et al [57] have recently developed an anisotropic constitutive model for creep of single crystal Ni-base superalloys in the low-temperature and high-stress creep regime. They used uniaxial creep data for the Ni-base single crystal superalloy ERBO 1C, [3] published by Wollgramm et al [58] for h100i-, h110i-, and h111i-tensile directions, to tune the parameters of the coupled set of differential equations in their model. [57] For the present work, this model was implemented into a user-defined subroutine UMAT of the FEM software package ABAQUS 6.11.…”

Section: B Anisotropic Creep Stress Calculationsmentioning

confidence: 99%

On Shear Testing of Single Crystal Ni-Base Superalloys

Eggeler

Wieczorek

Fox

et al. 2018

Metall Mater Trans A

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Shear testing can contribute to a better understanding of the plastic deformation of Ni-base superalloy single crystals. In the present study, shear testing is discussed with special emphasis placed on its strengths and weaknesses. Key mechanical and microstructural results which were obtained for the high-temperature (T % 1000°C) and low-stress (s % 200 MPa) creep regime are briefly reviewed. New 3D stereo STEM images of dislocation substructures which form during shear creep deformation in this regime are presented. It is then shown which new aspects need to be considered when performing double shear creep testing at lower temperatures (T < 800°C) and higher stresses (s > 600 MPa). In this creep regime, the macroscopic crystallographic [11À2](111) shear system deforms significantly faster than the [01À1] (111) system. This represents direct mechanical evidence for a new planar fault nucleation scenario, which was recently suggested (Wu et al. in Acta Mater 144:642-655, 2018). The double shear creep specimen geometry inspired a micro-mechanical in-situ shear test specimen. Moreover, the in-situ SEM shear specimen can be FIB micro-machined from prior dendritic and interdendritic regions. Dendritic regions, which have a lower c¢ volume fraction, show a lower critical resolved shear stress.

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The effect of stress, temperature and loading direction on the creep behaviour of Ni-base single crystal superalloy miniature tensile specimens

Cited by 77 publications

References 68 publications

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

Microstructure and Mechanical Properties of CMSX-4 Single Crystals Prepared by Additive Manufacturing

How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

On Shear Testing of Single Crystal Ni-Base Superalloys

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