Real-Time X-Ray transmission microscopy of solidifying Al-In Alloys

Abstract

Real-time observations of transparent analog materials have provided insight, yet the results of these observations are not necessarily representative of opaque metallic systems. In order to study the detailed dynamics of the solidification process, we develop the technologies needed for real-time Xray microscopy of solidifying metallic systems, which has not previously been feasible with the necessary resolution, speed, and contrast. In initial studies of Al-In monotectic alloys unidirectionally solidified in an X-ray transparent furnace, in situ records of the evolution of interface morphologies, interfacial solute accumulation, and formation of the monotectic droplets were obtained for the first time: A radiomicrograph of AI-30In grown during aircraft parabolic maneuvers is presented, showing the volumetric phase distribution in this specimen. The benefits of using X-ray microscopy for postsolidification metallography include ease of specimen preparation, increased sensitivity, and three-dimensional analysis of phase distribution. Imaging of the solute boundary layer revealed that the isoconcentration lines are not parallel (as is often assumed) to the growth interface. Striations in the solidified crystal did not accurately decorate the interface position and shape. The monotectic composition alloy under some conditions grew in an uncoupled manner.

Real Time Synchrotron Microradiography of Dendrite Coarsening in Sn-13 Wt Pct Bi Alloy

“…During the past few years, synchrotron microradiography has been applied to the real time study of solidification of real alloys by a number of other researchers. [14][15][16][17][18][19] This technique uses the high penetrating power of X-rays to look through a solidifying alloy sample. The microradiography technique we developed to observe alloy solidification in real time was described in detail elsewhere, [12,13] and here we only give a brief introduction of the experimental method.…”

Dynamics of solid/liquid interface shape evolution near an insoluble particle—An X-ray transmission microscopy investigation

“…Further details on the X-ray transmission microscope and experimental operations are discussed elsewhere. [10] The two different systems investigated for this study are 99.999 pct Al with 500-m-diameter ZrO 2 particles and 99.999 pct Al with 1000-and 500-m-diameter voids. The voids in the Al sample were simulated by drilling holes of desired diameters.…”

Multiphase solidification in multicomponent alloys

“…On the experimental side the detailed analysis of nucleation events during transient growth stages is not easy, especially for metallic alloys where direct observation of the solid/liquid interface is not straight forward: From several real time and in situ techniques that have been developed for detecting the solid/liquid interface in metallic alloys [248][249][250][251] one alone is able to measure not only the position but also the temperature of the advancing interface and thus nucleation undercooling in bulk samples: This method was developed by Salvi [252] and Garandet [253] and is based on the measurement of the Seebeck voltage and electrical resistance of the solidifying sample with reference to a sample that contains a non-moving solid/liquid interface. All these techniques are rather new.…”