Kinetics of Healing in a ZA-8 Shape Memory Alloy Composite

Cameron Ahles and James Veltri, “Kinetics of Healing in a ZA-8 Shape Memory Alloy Composite”
Mentors: Pradeep Rohatgi and Masum Bellah, Mechanical Engineering
Poster #1

Self-healing metal matrix composites (SHMMCs) is an emerging area of materials engineering research, showing promise especially in aerospace and a multitude of interdisciplinary engineering industries. These composites, however, have inherent difficulties that limit their reliability and functionality. Among them is a lack of understanding about healing kinetics, models for which have not yet been developed or thoroughly investigated. Experimentation has been done on a variety of metal matrix materials, with the research work focusing on determining ideal microstructure for healing and most effective healing mechanisms. This work, however, hopes to understand the kinetics of healing for a ZA-8 alloy. The specimen has inside several Nickel-Titanium (Nitinol) wires that when heated to its transformation temperature, will close a crack in the sample. From there, the entire composite must be heated to a partially liquidus temperature so that the matrix material can fill the crack and ideally restore its mechanical properties.  The methodology of experimentation is as follows. For each trial, the sample will be tested against a 3-point bend test until failure—that is, a complete crack of the alloy. Next, the sample will be heated to the healing temperature of the Nitinol wires, during which a camera will track the motion of the sample as it returns to its original state. Then the sample will be reheated to 385°C such that the matrix material will effectively diffuse Ultimately, the work aims to assess the relationship between healing temperature time and the strength recovery of the element. What is more, this work will examine the impact of volume percentage of Nitinol wires. It is expected that the higher the wire volume percentage, the better the strength recovery.