Journal article
Stretching Oriented Microstructures to Accelerate Rayleigh Instability During Rapid Thermal Processing for Generating Thixotropic Material
Metallurgical and materials transactions. A, Physical metallurgy and materials science, v 56(7), pp 2557-2569
01 Jul 2025
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
While molten thermoplastics require high shear-rate processing to reduce viscosity for extrusion, molten metals are incompatible due to very low viscosity. Instead, we can use semi-solid alloys containing a thixotropic microstructure to achieve the desired flow behavior for extrusion. However, large globular grains can clog small nozzle openings, limiting resolution. Current methods to achieve thixotropic microstructure rely on slow globularization mechanisms, resulting in relatively large grains in the semi-solid state (> 50 mu m). Processing using instability mechanisms can reduce the time required for globularization and produce smaller globules (< 10 mu m). Through this study, we demonstrate that during the rapid thermal processing of drawn wires, the instability mechanisms accelerate when the wire radius decreases. We stretched drawn wires of a Zn-Al alloy until necking and performed heat treatments in a molten salt bath at two different temperatures (400 degrees C and 450 degrees C). We observed that globularization proceeded faster as the sample diameter reduced and the salt bath temperature increased. The earlier onset of Rayleigh instability also decreased the initial grain size. The result was that the tip of the tensile samples heated to 450 degrees C produced similar to 5 mu m size globular grains within 1 second. A small grain size can enable smooth material flow through smaller dies and nozzles.
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Details
- Title
- Stretching Oriented Microstructures to Accelerate Rayleigh Instability During Rapid Thermal Processing for Generating Thixotropic Material
- Creators
- Sathyanarayan Sairam Jaishankar - Georgia Institute of TechnologyDonggang Yao (Corresponding Author) - Georgia Institute of TechnologyJack G. Zhou - Drexel University
- Publication Details
- Metallurgical and materials transactions. A, Physical metallurgy and materials science, v 56(7), pp 2557-2569
- Publisher
- Springer Nature
- Number of pages
- 13
- Grant note
- 2027871; 2027823 / National Science Foundation; National Science Foundation (NSF)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- [Retired Faculty]; Mechanical Engineering and Mechanics
- Web of Science ID
- WOS:001489783500001
- Scopus ID
- 2-s2.0-105005111578
- Other Identifier
- 991022197319304721
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Materials Science, Multidisciplinary
- Metallurgy & Metallurgical Engineering