In Situ Observation of Material Failure in Cast Aluminum Alloy During Monotonic Loading Observed by a High-Speed Camera

In situ observation of the failure characteristics of a cast aluminum alloy has been conducted using a testing system with a high-speed camera. The failure process of the cast Al alloy was captured clearly with an high image resolution (1,024 × 1,024 pixels) at a high frame rate (20,000/s), where the specimen surface for observation was dyed dark using a black oil-based ink. A dark curtain was set behind the test specimen as background. Strong lighting of about 10 klx was used, which was applied to the dark specimen surface for clarification of material failure. The aim of this approach was to detect the failure characteristics or failure objects with bright zone. Using this system, both debris particles flying from the fracture sample and dislocation-like movements were detected. These were observable as tiny bright dots. The flying debris particles of about 35 μm in diameter consisted mainly of Si- and Fe-based eutectic structures. The flying speed of the debris particles was about 1,800 mm/s and their flight distance from the specimen was about 100 mm. The velocity of the dislocation-like movements was found to be less than 1,000 mm/s, and this motion was seen repeatedly before and after sample failure occurred.