LLNLの物理学者が、チタンの寿命を縮める「ドウェル疲労」の原因を解明(LLNL physicist probes causes of life-shortening ‘dwell fatigue’ in titanium)


2022-11-11 ローレンスリバモア国立研究所(LLNL)

Nature Communications誌に掲載されたこの研究では、Ti3Alが秩序化を示すところでは、関連する応力の大きさで滑りなだれがより激しくなることが示されている。一方、格子間酸素の量を増やすと、より小さな雪崩がより頻繁に発生するようになり、深刻さが軽減されるようである。


チタンのすべり断続性に及ぼす合金化の影響とドウェル疲労への示唆 The influence of alloying on slip intermittency and the implications for dwell fatigue in titanium

Felicity F. Worsnop,Rachel E. Lim,Joel V. Bernier,Darren C. Pagan,Yilun Xu,Thomas P. McAuliffe,David Rugg &David Dye
Nature Communications  Published:10 October 2022


Dwell fatigue, the reduction in fatigue life experienced by titanium alloys due to holds at stresses as low as 60% of yield, has been implicated in several uncontained jet engine failures. Dislocation slip has long been observed to be an intermittent, scale-bridging phenomenon, similar to that seen in earthquakes but at the nanoscale, leading to the speculation that large stress bursts might promote the initial opening of a crack. Here we observe such stress bursts at the scale of individual grains in situ, using high energy X-ray diffraction microscopy in Ti–7Al–O alloys. This shows that the detrimental effect of precipitation of ordered Ti3Al is to increase the magnitude of rare pri〈a〉 and bas〈a〉 slip bursts associated with slip localisation. By contrast, the addition of trace O interstitials is beneficial, reducing the magnitude of slip bursts and promoting a higher frequency of smaller events. This is further evidence that the formation of long paths for easy basal plane slip localisation should be avoided when engineering titanium alloys against dwell fatigue.