Accession Number : ADA305799

Title :   A Mechanistic Study of Microalloying Effects in NiAl.

Descriptive Note : Final rept. 1 Jul 91-31 Mar 95,

Corporate Author : GE AIRCRAFT ENGINES CINCINNATI OH ENGINEERING MATERIALS TECHNOLOGY LABS

Personal Author(s) : Darolia, R. ; Field, R. D. ; Noebe, R. D. ; Garg, A. ; Walston, W. S.

PDF Url : ADA305799

Report Date : 31 MAY 1995

Pagination or Media Count : 212

Abstract : The objective of this study was to determine the mechanisms for ductility improvements in NiAl resulting from low level alloying additions (less than or equal 0.1 at% of Mo, Ga, Fe, etc.) and low temperature heat treatments, and the relationship between these phenomena and embrittling effects of interstitial impurities. The approach taken was to investigate the effect of micro alloying additions on deformation behavior in single crystals. This included slip systems, critical resolved shear stresses (CRSS), and tensile ductility as a function of crystallographic orientation and temperature. TEM studies were also performed to determine dislocation structures. Investigations of point defects and their interactions with dislocations were pursued. These included resistivity measurements as well as internal friction studies. In the course of this study, serrated yielding was observed suggesting dislocation/point defect interactions. Further study of the strain aging phenomenon was carried out as a function of composition, specimen heat treatments, test temperature and strain rates. In addition, the effect of multiple microalloying additions on ductility was studied on an alloy containing 0.1 at% Fe and 0.05 at% Ga. The effect of impurities on the deformation behavior of NiAl was studied by utilizing ultra-high purity single crystals. Studies were also carried out to better understand the deformation behavior in a strong NiAl alloy. A considerable amount of scatter in the room temperature tensile ductility was observed throughout the course of this study. A systematic study of the cause of scatter was undertaken which included the effect of composition, especially carbon content, batch to batch variation, specimen machining, specimen surface preparation after machining and specimen alignment in the tensile test set up. jg p3

Descriptors :   *ALLOYS, *NICKEL, *DUCTILITY, *ALUMINIDES, TEST AND EVALUATION, MEASUREMENT, LOW TEMPERATURE, MACHINING, INTERACTIONS, RESISTANCE, DEFORMATION, TENSILE PROPERTIES, STRUCTURES, SINGLE CRYSTALS, MOLYBDENUM, EMBRITTLEMENT, CARBON, POINT DEFECTS, IMPURITIES, INTERSTITIAL, ROOM TEMPERATURE, HEAT TREATMENT, STRAIN RATE, IRON, SURFACES, DISLOCATIONS, SHEAR STRESSES, LOW LEVEL, GALLIUM, BATCH PROCESSING, TENSILE TESTERS, CRYSTALLOGRAPHY, INTERNAL FRICTION, TEST SETS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE