In-Situ Fracture Observation and Fracture Toughness Analysis of Ni-Mn-Ga-Fe Ferromagnetic Shape Memory Alloys

The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile γ particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contai...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2011-12, Vol.42 (13), p.3961-3968
Main Authors: Euh, Kwangjun, Lee, Jung-Moo, Nam, Duk-Hyun, Lee, Sunghak
Format: Article
Language:English
Subjects:
Alloys
Applied sciences
Characterization and Evaluation of Materials
Chemistry and Materials Science
Crack propagation
Exact sciences and technology
Ferroelectrics
Ferromagnetism
Fracture mechanics
Fracture toughness
Fractures
Homogenizing
Magnetism
Materials Science
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metallic Materials
Metals. Metallurgy
Nanotechnology
Nickel
Nickel base alloys
Scanning electron microscopy
Structural Materials
Surfaces and Interfaces
Thin Films
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Summary:The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile γ particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of γ particles in β grains after the homogenization treatment at 1073 K to 1373 K (800 °C to 1100 °C). With increasing homogenization temperature, γ particles were coarsened and distributed homogeneously along β grain boundaries as well as inside β grains. According to the in-situ microfracture observation, γ particles effectively acted as blocking sites of crack propagation and provided the stable crack growth, which could be confirmed by the R -curve analysis. The increase in fracture resistance with increasing crack length improved overall fracture properties of the Ni-Mn-Ga-Fe alloys. This improvement could be explained by mechanisms of blocking of crack propagation and crack blunting and bridging.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-011-0804-y