| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1986: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1985: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
This research project is aimed to examine fatigue and cyclic deformation behavior of a Cu-Fe alloy with iron precipitates. Three kinds of specimens, i.e., ( <i> ) as-quenched specimens made of a solid solution of Cu and Fe (specimen S), ( <ii> ) aged specimens with <gamma> -Fe precipitates (specimen G) and ( <iii> ) aged, deformed and annealed specimens with <alpha> -Fe precipitates (specimen A), were prepared for the fatigue tests. Both stress-controlled and strain-controlled fatigue tests were performed at room temperature.
Under the stress-controlled fatigue tests at various stress amplitudes, all specimens showed cyclic hardening behavior. It was very interesting to find that at a fixed stress amplitude, specimens G showed the longest fatigue life, followed in order by specimens A and S. A similar result was also obtained for the strain-controlled fatigue tests; speicmens G showed the longest fatigue life.
In order to reveal the reason why specimens G had the best fatigue resistance, fatigued specimens were observed on a transmission electron microscope. In general, specimens exhibited various dislocation structures characteristic of fatigued f.c.c. metals, such as loop patches, dipolar walls, cells, etc. It was found that in specimens G, the <gamma> -> <alpha> martensitic transformation in Fe particles occurred during the very initial stage of the fatigue tests and a complex dislocation structure was created around the particles in association with the transformation. Moreover, there was a distinct tendency that the dislocation structure was more developed in specimens S and A than in specimens G.
It was concluded, from the above experimental observations, that the complex dislocation tangles around the Fe particles in specimens G effectively impeded the development of a dislocation structure, resulting in a more uniform deformation and a longer fatigue life compared with specimens A and S.
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