Stress Exponent of Minimum Creep Rate and Activation Energy of Creep for Oxide Dispersion-strengthened Nickel-based Superalloy MA754

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

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Process optimization and mechanical properties of oxide dispersion strengthened nickel-based superalloy by selective laser melting

Materials & Design ◽

10.1016/j.matdes.2019.108418 ◽

2020 ◽

Vol 188 ◽

pp. 108418 ◽

Cited By ~ 3

Author(s):

Guowei Wang ◽

Lan Huang ◽

Zecheng Liu ◽

Zijun Qin ◽

Wuqiang He ◽

...

Keyword(s):

Mechanical Properties ◽

Selective Laser Melting ◽

Process Optimization ◽

Oxide Dispersion Strengthened ◽

Oxide Dispersion ◽

Laser Melting ◽

Nickel Based Superalloy

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Creep and Fracture Mechanisms in an Oxide-Dispersion Strengthened Ni3Al-Based Alloy Between 649°C and 982°C

MRS Proceedings ◽

10.1557/proc-364-861 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 3

Author(s):

Ralph P. Mason ◽

Nicholas J. Grant

Keyword(s):

Stress Exponent ◽

High Stress ◽

Oxide Dispersion Strengthened ◽

Fracture Mechanisms ◽

Oxide Dispersion ◽

Creep Tests ◽

Creep Mechanisms ◽

Stress Region ◽

Power Law Creep ◽

Reported Data

AbstractAn oxide-dispersion strengthened (ODS) Ni3Al-based alloy has been fabricated and creep tested. Previously reported data for minimum creep rate as a function of stress indicated that two creep mechanisms operate at intermediate temperatures of 732 and 816°C [1]. This paper reports the results of recent interrupted creep tests and fractographic studies which serve to identify the two creep mechanisms. Creep at low stresses or low creep-rates occurs by constrained growth of cavities on transverse grain boundaries. In this low stress region an apparent stress exponent of 5.1 is observed. Creep at high stresses or high creep-rates results from the bulk deformation of grains by power law creep with a much smaller contribution due to grain boundary cavitation. The stress exponents of 13 and 22 observed in this high stress region are typical of ODS alloys. In both regions fracture is observed to be mixed mode with a large transgranular component due to the high grain aspect ratio developed in this material. Limited data at 982°C indicate the occurrence of only one mechanism which can be described by a stress exponent of 9.1. It was not possible, based on fractographic studies, to associate the creep mechanism at 982°C with either of those observed at the intermediate temperatures. No fractographic studies were performed at 649°C due to lack of valid specimens; however, the stress exponent of 13.5 observed at 649°C suggests that creep occurs by deformation of the grains.

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