NBS Misc. Publ. 260-10, Standard Reference Materials: Homogeneity Characterization of NBS Spectrometric Standards II: Cartridge Brass and Low-Alloy Steel, December, 1965. 30 cents.* NBS Misc. Publ. 260-11, Standard Reference Materials: In press. Send orders with remittance to: Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. 20402. Remittance from foreign countries should include an additional one-fourth of the purchase price for postage. PART I: WHITE CAST IRON REFERENCES CONTENTS TABLE 1. Certified composition values for SRM 1175, white cast iron (Fe by difference is 87.22%) 1. 2. FIGURES NBS-SRM 1175, white cast iron. (X500) PAGE 2 3 4 5 6 777 8 8 8 9 9 10 1. ત Twenty second count totals of points in FIGURES 1. Final submitted stainless steel powder compact. Unetched X750 11 12 2. X-ray scanning displays for Fe, Cr and Ni 13 STANDARD REFERENCE MATERIALS: HOMOGENEITY CHARACTERIZATION OF NBS SPECTROMETRIC H. Yakowitz, D. L. Vieth, R. E. Michaelis Institute for Materials Research ABSTRACT This paper describes a continuation of the NBS effort to characterize metal materials as to their suitability for use in calibrating microanalytical techniques such as the solids mass spectrometer and, especially, the electron probe microanalyzer. An NBS white cast iron sample (SRM 1175) and a specially prepared stainless steel powder metallurgy compact have been investigated by means of electron probe microanalysis and optical metallography. Results for six elements in the cast iron and three in the stainless steel are given. It is concluded that neither of these materials is suitable for use for calibration in microanalytical techniques. It is emphasized, however, that this in no way affects the usefulness of the white cast iron material for macroanalytical techniques such as optical emission and x-ray spectrochemical analysis. Key words: microanalytical techniques, solids mass spectrometer, electron probe microanalyzer, NBS white cast iron sample (SRM 1175), stainless steel powder metallurgy compact, optical metallography, macroanalytical techniques, optical emission, x-ray spectrochemical analysis PART I: WHITE CAST IRON In the continuing program to characterize existing NBS Standard Reference Materials as to their suitability for microanalytical techniques such as for the electron probe microanalyzer and the solids mass spectrometer, the white cast iron designated SRM 1175 [1] was investigated. The certified composition values for this material are given in table I [2]. It was decided to investigate the homogeneity of several elements by taking mechanical line scans with the electron probe microanalyzer in precisely the same manner as was done on NBS-SRM standards for brass and for low-alloy steel [3]. A portion of the chill-cast face was prepared metallographically by grinding on Sic papers through 600 grit and polishing to a final finish on 6- and 0.25-micron diamond respectively. No pits or inclusions were observed; as expected, etching revealed no smeared metal. The resultant structure is shown in figure 1. After removing the etch on 0.25 micron diamond, the sample was introduced into the electron probe microanalyzer. Mechanical line scans were taken for six of the eighteen certified elements: namely, Mn, Si, Ni, Cr, Mo and Fe. Portions of each of these traces are shown in figure 2; the total sample length examined for each element ranged from 1.2 to 2.0 mm. The traces show that the elements investigated are not homogeneously distributed at micron levels of spatial resolution. Therefore, SRM white cast iron 1175 is not considered suitable for microanalytical techniques in that reproducible results do not appear possible. It is emphasized, however, that this in no way affects the usefulness of Standard Reference Material 1175 for macroanalytical techniques such as optical emission and x-ray spectrochemical analysis in which a large portion of the chill-cast face is sampled. Further detailed information on the macrohomogeneity of this material may be obtained from reference [1]. REFERENCES [1] R. E. Michaelis and L. L. Wyman, Standard Reference Materials: Preparation of NBS White Cast Iron [2] [3] Spectrochemical Standards, NBS Misc. Publ. 260-1, 31 J. I. Shultz, Standard Reference Materials: Methods |