Textural Evolution During Dynamic Recovery and Static Recrystallization of Molybdenum
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INTRODUCTION
SINCE the beginning of the twentieth century, technically pure molybdenum has been used as a hightemperature material due to its melting point of TM = 2893 K (2620 C).[1] Besides typical high-temperature applications, several additional uses at ambient temperatures have been established during the last decades because of molybdenum’s further outstanding physical and chemical properties. Two prominent new fields are electronics and coating technology. For the sputtering of molybdenum layers in thin-film-transistor liquid-crystal displays and photovoltaic cells, large molybdenum plates are required. These plates are produced by thermomechanical processing of sintered starting material.[1] Therefore, the microstructural evolution, such as recrystallization behavior and textural evolution during hot deformation of molybdenum sinter plates, has to be studied in greater detail in order to be able to produce large plates with homogeneous properties. The recrystallization behavior of molybdenum has previously been studied.[2–4] Unfortunately, such studies SOPHIE PRIMIG, Ph.D. Student, and HARALD LEITNER, Senior Scientist, are with the Christian Doppler Laboratory for Early Stages of Precipitation, University of Leoben, Franz-Josef-Strasse 18, Leoben 8700, Austria, and also with the Department of Physical Metallurgy and Materials Testing, University of Leoben. Contact e-mail: sophie. [email protected] WOLFRAM KNABL and ALEXANDER LORICH, Employees, are with the PLANSEE SE, Reutte 6600, Austria. HELMUT CLEMENS, Professor, is with the Department of Physical Metallurgy and Materials Testing, Montanuniversita¨t Leoben, Leoben 8700, Austria. ROLAND STICKLER, Emeritus Professor, is with the University of Vienna, Vienna 1090, Austria. Manuscript submitted December 13, 2011. Article published online July 10, 2012 4794—VOLUME 43A, DECEMBER 2012
were mainly carried out after cold deformation using molybdenum exhibiting higher impurity contents than the material available nowadays. Guttmann[2] studied cold-deformed and annealed molybdenum specimens using a transmission electron microscope (TEM). He reported subgrain growth, subgrain coalescence, and strain-induced boundary migration as nucleation mechanisms. Estulin and Demkin[3] traced subgrain boundaries in compressively deformed molybdenum bars by etch pitting and found some hints for the coalescence of subgrains. Pink[4] published a recrystallization diagram using cold-deformed and subsequently annealed tensile specimens. Limited studies on hot-deformed specimens of pure molybdenum[5] or its alloys[6] revealed a recoverycontrolled hot-deformation behavior due to the high stacking fault energy of molybdenum.[7] However, stateof-the-art experimental methods as large area electron backscatter diffraction (EBSD) scans have not yet been applied. EBSD is a powerful tool since it determines crystallographic orientations and produces further data that can be used to study deformation, recovery, and recrystallization.[8] This is important since texture and recrystallizatio
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