Trapping of Sb by TiC precipitates in Fe
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studied, and the microscopic scale of the alloys facilitated measurements at temperatures approaching the regime of temper embrittlement. 1. EXPERIMENTAL DETAIL Samples were prepared from polycrystalline Fe or Fe-0.1 wt pct Ti of specified purity 99.97 wt pct. The quoted concentrations of C and N were 0.003 and 0.0008 wt pct for the Fe-Ti alloy and a portion of the Fe, and 0.0012 and 0.0010 wt pet for the remainder of the Fe. The ion beam analysis experiments employed discs of diam 10 mm and thickness "~2 mm. The faces of these discs were mechanically polished, and the specimens were then annealed at 1150 K for ~ 16 h to remove damage and enlarge the grains. Surface faceting after this anneal indicated a grain size of "~0.1 to 1 mm. The transmission electron microscopy studies utilized 0.05 mm Fe foil which had been annealed for ~ 16 h at 1130 K and then electropolished. The Fe specimens were alloyed to depths of ~ 100 nm by ion implanting Sb, Ti, and C at room temperature. The ion fluences varied between 0.3 and 1.0 • 1017at./cm% and the implantation energies were in the range 50 to 180 keV. The implantation chamber was turbo-pumped to ~ 4 • 10-4 Pa, with ) 9 0 pet of the residual gas being Ar from the ion source. All annealing was carried out under an ion-pumped vacuum of < 10 -4 Pa.
Depth profiling of Sb and Ti was accomplished by Rutherford backscatterings with 2.6 MeV 4He at room temperature. Each sequence of repeated annealing and analysis was carried out on a single sample, with the 1 mm x 1 mm beam spot being fixed. As a check on analysis beam effects, the backscattering measurement was periodically repeated for a fresh spot on the sample; no significant difference in the depth profiles was ever observed. In certain cases, the total quantity of C within the implanted region was also measured by means of the deuterium-excited nuclear reaction 12C(d,p)~3C (Ref. 6). Transmission electron microscopy was used to char-
ISSN 0360-2133 / 80/0811-1465500.75 / 0 METALLURGICAL TRANSACTIONS A 9 1980 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME 11A, AUGUST 1980--1465
acterize the microstructure within the implanted layer. Foils were thinned from the unimplanted side following implantation and annealing, and were characterized using standard selected-area diffraction and dark-field imaging techniques at 100 kev. 2. R E S U L T S A N D I N T E R P R E T A T I O N In this section the observed depth profiles and microstructures of implanted Fe-Ti-C-Sb alloys are considered as a function of annealing. The objective is to characterize interactions between Sb and TiC precipitates within the Fe matrix. The first subsection presents data demonstrating that Sb is bound within the Ti-rich region of the implanted Fe. The second subsection presents evidence that this effect is due to the presence of TiC precipitates. In the third subsection a theoretical model of solute migration in the presence of precipitate traps is developed, and in the fourth subsection this theory is used to analyze the experim
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