MSE Seminar: Xiang Chen, "Plum Puddings" with Intelligence - A Study of Inclusion Effects in Shape-Memory Structures

Abstract

This presentation covers three projects on the inclusion effects in shape memory alloys/structures. The 1st project numerically simulates the stress field underlying TRansformation-Induced Defects (TRID) in single crystal NiTi micropillar compression, and compares the simulation results with scanning TEM observations. The close correlation between experimental and numerical results provides further mechanistic insight into this intriguing phenomenon. The 2nd project focuses on the link between aging-induced H-phase precipitates in Ni-Ti-Hf high temperature SMA and the thermo-mechanical properties of the alloy. By incorporating the latest advances both in characterization and in fundamental simulations in the a Microstructural Finite Element (MFE) model, we quantitatively reproduce the over-aged behavior, and provide a mechanistic explanation for the mystery in optimally-aged samples. The 3rd project studies the behavior of a NiTi(fiber)/Al(matrix) composite (aimed at achieving zero thermal expansion) fabricated through an emerging low-temperature welding technique -- Ultrasonic Additive Manufacturing (UAM). By exploring different hypothetical scenarios in our MFE model, we identify roles played by different parameters such as the fiber texture, bonding strength of matrix-fiber interface, and aspect ratio of the fibers.

Bio

Xiang (approx. pronounced "Sean") is an eternally curious person. Born and raised in South China, he developed his interest in the science and engineering in junior high school, when he took part in a municipal invention contest. He asks a lot of questions, but essentially there are just two: "Why?" and "How to do it?". He spent most of his past ten years searching for answers to "Why?", and he plans to move on to THE next question after his graduation from THE Ohio State University.