Can Castings Heal Themselves?
The capacity of bones to heal their own cracks inspired researchers to apply the concept to cast metals.
Jose Martinez-Lucci, Andrew Ruzek, Shobhit Misra, Pradeep Rohatgi and Ryo Amano Univ. Of Wisconsin-Milwaukee, Milwaukee, Wisconsin
strategies in the development of self-healing metallic systems have incorporated shape memory alloy (SMA) reinforcements in cast metals and induced the formation of precipitates in an oversaturated but under-aged alloy.
T
hree methods of creating metal castings that can heal cracks in themselves are being devel- oped at the University of Wisconsin-Milwaukee (UWM), Milwaukee. While the technology is in its infancy, the main
To put it simply, a material must have three things to heal
itself: a structure that maintains functionality, parts that move to close voids and a trigger to activate this healing action. The three strategies being pursued at UWM are: • incorporating SMA wires in castings; • using molten interdendritic eutectic to seal surface cracks; • embedding micro-balloons and micro-tubes contain- ing a low melting point alloy in the matrix of a high melting point casting.
Fig. 1. Shown is an optical microscopy of randomly orientated NiTi fibers in a Sn-20% Bi matrix synthesized at UWM.
24 Metal Casting Design anD PurChasing
Fig. 2. This scanning electron microscope image shows the crack surface of the NiTi short fiber reinforced Sn-20% Bi matrix.
July/august 2011
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