Thermal Aging Effects on the Mechanical Properties of As-Cast Ni₃Al-based Alloy

Journal Article · Sun Jan 01 00:00:00 EST 2006 · Materials Science and Engineering A

DOI:https://doi.org/10.1016/j.msea.2006.05.007· OSTI ID:1003549

Lee, Dongyun ^[1]; Santella, Michael L ^[1]

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1. ORNL

A series of tensile tests were conducted at room and elevated temperatures on specimens of the alloy known as IC221M (Ni-8.2Al-7.6Cr-1.5Mo-2.1Zr, wt%). Specimens were tested in the as-cast condition or after aging in either air or Ar for up to 1000 h at 900-1100 XC. Room temperature yield strength decreased continuously with aging time at 900 XC from the as-cast value of 530 MPa to 320 MPa after 1000 h. A similar trend was found for hardness. The strength reductions with aging time at 900 XC were similar for aging in either air or Ar. For aging at 1050 XC and 1100 XC, aging in air caused significant strength loss that was attributed to aggressive oxidation. The room temperature yield strength of specimens aged in Ar increased for aging at 1050 XC and 1100 XC. Microhardness testing also showed that specimens aged at 1100 XC had higher hardness than those aged at 900 XC. Analysis using equilibrium thermodynamics suggested that the increases of yield strength and hardness resulted from increasing the amount of fine S precipitation in the alloy matrix. For testing at elevated temperatures, the as-cast alloy had room temperature yield strength of 530 MPa that increased continuously up to a value of 650 MPa at 700 XC. Aging in Ar for 1000 h at 900 XC resulted in a room temperature yield strength of 320 MPa that increased to 560 MPa at 700 XC and decrease slightly to 550 MPa at 900 XC. Aging in Ar for 1000 h at 1100 XC produced room temperature yield strength of 435 MPa that increased to 550 MPa at 500 XC and decreased continuously at high test temperatures. The behavior of these specimens was also rationalized using equilibrium thermodynamics to estimate the fractions of coarse and fine S particles in the microstructures.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1003549
• Journal Information: Materials Science and Engineering A, Vol. 428, Issue 1-2; ISSN 0921-5093
• Country of Publication: United States
• Language: English