Transmission Electron Microscope In Situ Straining Technique to Directly Observe Defects and Interfaces During Deformation in Magnesium

• Published in: JOM (1989) Vol. 67; no. 8; pp. 1721 - 1728
• Main Authors: Morrow, B. M., Cerreta, E. K., McCabe, R. J., Tomé, C. N.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.08.2015; Springer Nature B.V; Springer
• Subjects: Chemistry/Food Science; Deformation; Earth Sciences; Engineering; Environment; Experiments; in-situ mechanical testing; Magnesium; MATERIALS SCIENCE; Microstructure; Physics; Scanning electron microscopy; Studies; Transmission electron microscopy; transmission electron microscopy (TEM); twinning; Conventional Transmission Electron Microscopy; Dislocation Content; Twin Boundary; Twin Growth; Transmission Electron Microscopy Foil
• ISSN: 1047-4838; 1543-1851
• DOI: 10.1007/s11837-015-1432-6

In situ straining was used to study deformation behavior of hexagonal close-packed (hcp) metals. Twinning and dislocation motion, both essential to plasticity in hcp materials, were observed. Typically, these processes are characterized postmortem by examining remnant microstructural features after straining has occurred. By imposing deformation during imaging, direct observation of active deformation mechanisms is possible. This work focuses on straining of structural metals in a transmission electron microscope (TEM), and a recently developed technique that utilizes familiar procedures and equipment to increase ease of experiments. In situ straining in a TEM presents several advantages over conventional postmortem characterization, most notably time resolution of deformation and streamlined identification of active deformation mechanisms. Drawbacks to the technique and applicability to other studies are also addressed. In situ straining is used to study twin boundary motion in hcp magnesium. A 10 1 ¯ 2 twin was observed during tensile and compressive loading. Twin-dislocation interactions are directly observed. Notably, dislocations are observed to remain mobile, even after multiple interactions with twin boundaries; this result suggests that Basinki’s dislocation transformation mechanism by twinning is not present in hcp metals. The coupling of in situ straining with traditional postmortem characterization yields more detailed information about material behavior during deformation than either technique alone.