Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions
Name
49014623-MIT.pdf
Description
Full printable version
Size
1.93 MB
Format
Adobe PDF
Checksum (MD5)
b9264e2cf643fb600d232d3e11610768
Author(s)
Kuo, Long-Sheng, 1969-
Advisor(s)
Taiqing Qiu.
Date Issued
2001
Publisher
Massachusetts Institute of Technology
Abstract
Laser interactions with metals involve absorption of photon energy by electrons, energy coupling between electrons and the lattice, and energy transport by diffusion of electrons and lattice vibrations. During picosecond laser irradiation of metal films, electrons and the lattice are not in thermal equilibrium. On the other hand, rapid laser heating produces a large degree of superheating and undercooling during melting and solidification. First, this work investigates experimentally non-equilibrium heating processes during intense picosecond laser heating of metal films. Results show excellent agreement with predictions of the two-step radiation heating model. Second, this work develops a general model to characterize both non-equilibrium energy deposition and phase change processes. The predictions show that the non-equilibrium heating processes significantly increase the laser melting threshold, enlarge the thermal-affected region, reduce the lattice temperature rise, prolong the phase change duration, and reduce the solidification speed. These results are important for materials processing using ultrashort pulsed lasers.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (leaves 55-57).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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