Accession Number : AD0873832

Title :   Investigation to Develop a High Strength Eutectic Alloy with Controlled Microstructure.

Descriptive Note : Final rept. 1 Aug 69-31 Jul 70,

Corporate Author : UNITED AIRCRAFT RESEARCH LABS EAST HARTFORD CT

Personal Author(s) : Thompson, Earl R. ; George, Frederick D. ; Kraft, Edwin H.

Report Date : 31 JUL 1970

Pagination or Media Count : 89

Abstract : The Ni3Al (gamma') - Ni3Cb (delta) eutectic alloy was directionally solidified in a plane front manner at rates varying from 0.3 to 10.6 cph. The lamellar spacing which decreased with increasing rate affected the strength of the eutectic according to a Hall-Petch correlation. By decreasing the spacing by a factor of 4.7, the tensile strength was increased by 35 percent at room temperature and by 100 percent at 2000F. The eutectic grown at 10.6 cph possessed the phenomenal strength of 140,000 psi at 2000F. The resistance of the eutectic to a tension-tension fatigue cycle proved excellent. This resistance was provided by the strength of the phases, as well as the presence of debondable interfaces which affect crack propagation. Thermal fatigue tests conducted on the directionally solidified eutectic showed no adverse effect due to the differences in thermal expansion of the phases. Quenching the eutectic produced a res dual tensile stress in the gamma' which lowered the proportional limit of the composite. Studies of the strength anisotropy showed that the strength is decreased in directions nonparallel to the growth axis with brittle behavior at room temperature and ductile behavior at 2000F. (Author)

Descriptors :   (*NICKEL ALLOYS, EUTECTICS), (*EUTECTICS, COMPOSITE MATERIALS), ALUMINUM ALLOYS, NIOBIUM ALLOYS, INTERMETALLIC COMPOUNDS, MICROSTRUCTURE, FREEZING, FATIGUE(MECHANICS), PHASE STUDIES, HEAT RESISTANT ALLOYS, HEAT RESISTANT METALS.

Subject Categories : Laminates and Composite Materials
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE