CONSTITUTION, METALLURGY, AND OXIDATION RESISTANCE OF IRON-CHROMIUM- ALUMINUM ALLOYS
The constitution of iron-chromium -aluminum alloys was investigated employing high-purity materials. Ternary sections illustrating the results are presented. The limits of the alpha-plus-sigma region are found to extend from 33 to 63 wt.% chromium at 600 C. At 750 C these limits decreasc to 38 and 57 wt.% chromium. Sigma is found in alloys coataining a maximum of about 9 wt.% aluminum at 600 C and 4 wt.% aluminum at 750 C. The limits of the alpha solid-solution region were investigated between 500 and 900 C. No observable change in limits occurred between 500 and 750 C. However, between 750 and 900 C the AlCr/sub 2/ phase decomposes resulting in a slightly expanded alpha region in the high-chromium alloys. Sigma is found to be unstable below 600 C in alloys of sigma-phase composition. Sigma formation and decomposition occur reversibly above and below this temperature. The nature of the products of the reaction below 600 C has not been determined. A detailed investigation of the physical metallurgy of iron alloys containing 25 to 35 wt.% chromium and 3 to 8 wt.% aluminum, has been made in an attempt to define the limits of usefulness of these materials as structural materials. It is possible to melt and fabricate all alloys within this composition range, but extraordinary care must be used to avoid embritilement from undesirable impurities such as carbon, from oxide drosses, from un favorable grain size and structure, and from internal cracking caused by rapid cooling. Suitable methods for casting and fabricating these alloys are described. The deformation processes of iron-chromium -aluminum alloys are reported and a ductility transition which varies with alloy content is attributed to the interaction of a twinning mode of plastic deformation and a cleavage mode of fracture. The oxidation resistances of iron23.7 wt.% chromium- 6.0 wt.% aluminum alloy and of nickel-20.0 wt.% chromium-1.1 wt.% niobium alloy have been compared at 1040 and 1150 C in air atmospheres containing additions of (1) water vapor, (2) carbon dioxide, and (3) combinations of water vapor and carbon dioxide. The iron-chromium-aluminum alloy was more oxidation resistant than the nickel-chromium -niobium alloy in all atmospheres at 1150 C. Minimum oxidation of both alloys occurred in an atmosphere of air plus 2.5 vol.% water vapor. (auth)
- Research Organization:
- Battelle Memorial Inst., Columbus, OH (United States)
- DOE Contract Number:
- W-7405-ENG-92
- NSA Number:
- NSA-13-002969
- OSTI ID:
- 4290548
- Report Number(s):
- BMI-1298
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- United States
- Language:
- English
Similar Records
PROGRESS RELATING TO CIVILIAN APPLICATIONS DURING FEBRUARY 1960
THE SOLID SOLUBILITY AND CONSTITUTION OF YTTRIUM IN IRON-20 TO 40 w/o CHROMIUM ALLOYS
Related Subjects
AIR
ALUMINUM ALLOYS
BRITTLENESS
CARBON
CARBON DIOXIDE
CASTING
CHROMIUM ALLOYS
COOLING
CRACKS
DECOMPOSITION
DEFORMATION
DUCTILITY
FABRICATION
FAILURES
GRAIN SIZE
HIGH TEMPERATURE
IMPURITIES
INTERMETALLIC COMPOUNDS
IRON ALLOYS
MELTING
METALLURGY
NICKEL ALLOYS
NIOBIUM ALLOYS
OXIDES
PHASE DIAGRAMS
SOLID SOLUTIONS
STABILITY
STANDARDS
TEMPERATURE
THERMODYNAMICS
VAPORS
WATER