Accession Number : ADA184286

Title :   Metallurgical Investigation of Hot Ductility Loss in Ti-6211 Alloy.

Descriptive Note : Final technical rept. Jun 79-Jan 86,

Corporate Author : LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA

Personal Author(s) : Lewis,R E

PDF Url : ADA184286

Report Date : 15 Jan 1986

Pagination or Media Count : 196

Abstract : A preliminary metallurgical investigation of the hot ductility dip phenomenon in the Ti-6211 alloy was conducted. The main characteristic of this phenomenon is a low (0 to 20%) reduction in area of hot ductility specimens which are thermally cycled to about 1649 C and broken in tension on cooling to between 760 and 843 C. Low hot ductility is also exhibited by specimens from weld metal on heating directly to 760 to 843 C. The metallurgical investigation included fractographic and microstructural examination of a number of tested hot ductility specimens supplied by DTNSRDC-Annapolis, representing weld thermal cycles in 5.08-cm. thick, beta-processed plate, weld fusion zone, and 15.2- x 15.2- cm castings of Ti-6211. Also included were thermally cycled specimens of Ti-6Al amd Ti-50, a commercial purity alloy. This examination showed that intergranular fracture along prior beta-grain boundaries was predominant in specimens exhibiting the low hot ductility. Intergranular fracture appears to occur as the result of microvoid nucleation and coalescence at the edge of or near the edge of the gain boundary alpha layer present in the prior beta-grain boundary. Transmission electron microscopy revealed in one case a chain of small precipitates in this location; these disks are about 24 nm thick and spaced about 50 nm apart. Microprobe examination of sections through the boundaries did not reveal any significant local concentration of elemental species.

Descriptors :   *TITANIUM ALLOYS, *THERMAL STRESSES, *DUCTILITY, COALESCENCE, HIGH TEMPERATURE, LOSSES, CHAINS, PRECIPITATES, PURITY, FRACTOGRAPHY, MICROSTRUCTURE, FRACTURE(MECHANICS), CYCLIC TESTS, GRAIN BOUNDARIES, CRACKS, SULFUR, YTTRIUM, COOLING, BASE METAL, FUSION WELDING, WELDS, ZONE MELTING, CYCLES, THERMAL PROPERTIES, METALLURGY, TRANSMITTANCE

Subject Categories : Metallurgy and Metallography
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE