The HCP To BCC Phase Transformation in Ti Characterized by Nanosecond Electron Microscopy

The general class of martensitic phase transformations occurs by a rapid lattice-distortive mechanism, where kinetics and morphology of the transformation are dominated by the strain energy. Since transformation is diffusionless, phase fronts propagate through a crystal with great speed that can approach the speed of sound. We have observed a particular example of this class of phase transformation, the hexagonal close packed (HCP) to body centered cubic (BCC) transformation in titanium that is driven by a rapid increase in temperature. We have used a novel nanosecond electron microscope (the dynamic transmission electron microscope, DTEM) to acquire diffraction and imaging information on the transformation, which is driven in-situ by nanosecond laser irradiation. Using nanosecond exposure times that are possible in the DTEM, data can be collected about the transient events in these fast transformations. We have identified the phase transformation with diffraction patterns and correlated the time of the phase transformation with calculated conditions in the sample

Grundlagenuntersuchungen zur Strahlkontrolle bei Hochleistungsfestkoerperlasern Abschlussbericht

For separation of diagnosis beams from the main beam of high-performance solid state lasers a diffractive beam separator has been developed consisting of a quartz block. Into one face of the quartz block a grid of defined structure has been etched and the second face was coated with an antireflective layer. On the side front of the quartz block a focussing hologram is positioned regenerating the original sectional area of the main beam and enabling thus a real-time control of the spatial beam profil. The separation ratio (0.2%-1.1%) are independent on the power of the incident beam. The quality of the diagnosis beam is equal to that of the main beam. The grids are beam-resistant up to 2 kW. By application of such grid separators an improved performance control of the solid state laser system is achieved. (WEN)SIGLEAvailable from TIB Hannover: F97B845+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Festkoerper-Laser hoher mittlerer Leistung und Einkopplung in Fasern Abschlussbericht

Available from TIB Hannover: F95B549+a+b / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany); Commission of the European Communities (CEC), Brussels (Belgium)DEGerman

Hochleistungsdiodenlaser und diodengepumpte Festkoerperlaser - Analyse neuartiger Kristallstrukturen unter dem Einfluss hoher spektraler Leistungsdichten. Grundlegende Erforschung des Einsatzes diffraktiver Optiken im Resonatordesign am Beispiel des 1.44#mu#m Nd:YAG-Lasers Abschlussbericht

SIGLEAvailable from TIB Hannover: F02B1812 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman