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Doan, A. S., Jr.

Publications and source records attributed to Doan, A. S., Jr..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Remanent magnetization and structural effects due to shock in natural and man-made iron-nickel alloys

Explosive shock or meteorite impact are significant remagnetization processes. The mechanisms of remagnetization associated with the dynamic processes depend on the peak shock pressure, the nature of the shocked materials, and the behavior of the shock in the material. Magnetic measurements can be used to classify products formed during a shock process, and magnetic measurements can be used to investigate the process itself because of the special characteristics of the remanent magnetization vectors. The magnetic coercive force increases more rapidly in quenched and annealed iron-nickel alloys as nickel is added than it does in the alloys which have been shocked.

Wasilewski, P. J.↗
NASA NTRS1972

Quantitative simultaneous multi-element microprobe analysis using combined wavelength and energy dispersive systems

A combined WDS-EDS system obviates the severe X-ray peak overlap problems encountered with Na, Mg, Al and Si common to pure EDS systems. By application of easily measured empirical correction factors for pulse pile-up and peak overlaps which are normally observed in the analysis of silicate minerals, the accuracy of analysis is comparable with that expected for WDS electron microprobe analyses. The continuum backgrounds are subtracted for the spectra by a spline fitting technique based on integrated intensities between the peaks. The preprocessed data are then reduced to chemical analyses by existing data reduction programs.

Walter, L. S.↗
NASA NTRS1972

The effect of phosphorus on the formation of the Widmanstaetten pattern in iron meteorites.

Use of a combination of a revised Fe-Ni-P phase diagram and laboratory cooling experiments on Fe-Ni-P alloys to determine the effect of P on the formation of the Widmanstaetten pattern. From the phase diagram results, two reaction paths were found for the formation of kamacite (1) gamma (taenite) yields alpha (kamacite) + gamma (taenite) and (2) gamma yields gamma + Ph /phosphide, (FeNi)3P/ yields alpha + gamma + Ph. The reaction path gamma yields alpha + gamma is preferred at low P contents, while at higher P contents and at Ni contents greater than 7.0 wt.%, the reaction path gamma yields gamma + Ph yields alpha + gamma + Ph controls the formation of kamacite. Above 7 wt.% Ni, the effect of P on the equilibrium nucleation temperature of kamacite is quite small, less than about plus or minus 30 C with respect to the Fe-Ni binary diagram. The addition of P (greater than 0.1 wt.%) to meteorites promotes nucleation of kamacite at higher temperatures and effectively lowers the amount of undercooling necessary to nucleate kamacite homogeneously. Ni has just the opposite effect, decreasing the temperature of nucleation and increasing the amount of undercooling. It is concluded that significant amounts of undercooling, 50 to 100 C, are necessary for the nucleation of the Widmanstaetten structure in meteorites, and that chemical equilibrium is maintained in the various phases of slowly cooled iron meteorites to 650 C and probably to 600 C.

Goldstein, J. I.↗