Characterization of INCONEL alloy MA 6000 powder
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I.
INTRODUCTION
M E C H A N I C A L alloying (MA) is a dry, high-energy ball milling process that produces composite metal alloy powders with a uniform dispersion of refractory particles in a complex alloy matrix. 1These powders must be consolidated and worked under conditions which leave them with a high level of stored energy. Further thermo-mechanical and heat treatments are given to the alloys to optimize their grain structure and properties for their intended use. 2-5 The mechanical alloying process is being used to produce several oxide-dispersion-strengthened (ODS) superalloys as well as MA aluminum alloys. 4'6-9 The mechanical alloying process is usually carried out in high-energy attrition mills or special ball mills. The process occurs by repeated welding, fracturing, and rewelding of a mixture of elemental and master alloy powder particles in a highly energetic ball charge. When the conditions within the high-energy mill are properly maintained, a balance is eventually achieved between the welding and the fracturing of powder particles so that the overall particle size of the composite powder remains constant. The continued plastic deformation and fracturing leads to progressive refinement of the internal structure of the powder. Optical metallography can reveal a progressive refinement of the intemal structure within individual powder particles; lamellar structures are observed consisting of welded layers of the starting metal powder ingredients with high concentrations of the refractory particles trapped at the weld interfaces. The mechanical alloying process is regarded as complete in general, when the composite particles can no longer be resolved optically for their fine lamellar structure. Hence, the MA powder at this stage of processing is expected to be chemically and microstructurally homogeneous and heavily cold-worked as a result of attrition or ball milling. 3'4'~ In the present paper, an in-depth characterization of INCONEL alloy MA 6000 powder is discussed in terms of microstructure, phase identification, chemical homogeneity, degree of mechanical working, and surface chemistry. This information is necessary to have a better understanding of a basic mechanism of mechanical alloying as well as to
*INCONEL is a trademark of the INCO family of companies. S.K. KANG is Research Staff Member with IBM Research Center, P.O. Box 218, Yorktown Heights, NY 10598. R. C. BENN is Senior Metallurgist with lnco Alloys International, Inc., Huntington Alloy, P.O. Box 1958, Huntington, WV 25720. Manuscript submitted February 13, 1986. METALLURGICAL TRANSACTIONS A
provide guidelines for powder quality control. INCONEL alloy MA 6000 is an advanced ODS Ni-base superalloy having a nominal composition of Ni-15Cr-4.5A1-2.5Ti2Mo-4W-2Ta-0.15Zr-0.01B-0.05C- 1.1Y203, in wt pct. 10,11 II.
EXPERIMENTAL PROCEDURES
A. Materials Elemental Ni, Cr, W, Mo, and Ta powders were blended with preground Ni-A1, Ni-A1-Ti, Ni-B, and Ni-Zr master alloys and Y203. Powder batches were then mechanically alloyed in attritor mills unde
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