Accession Number : AD0835831

Title :   INTERSTITIAL SINK EFFECTS IN COLUMBIUM ALLOYS.

Descriptive Note : Technical rept. 1 Jun 66-31 Dec 67,

Corporate Author : SOLAR SAN DIEGO CALIF

Personal Author(s) : Brentnall,W. D. ; Metcalfe,A. G.

Report Date : APR 1968

Pagination or Media Count : 104

Abstract : The interstitial sink effect arises when precipitation strengthened columbium-base alloys are heated in contact with coatings, braze alloys and diffusion bonding intermediates containing significant amounts of Group IV elements; migration of interstitial elements from the refractory alloy to the sink takes place and considerable reductions in strength occur. In these studies, the coated condition was simulated by diffusion bonding 0.002- and 0.005-inch foils of pure titanium, Ti-30V and other titanium alloys, to 0.020-inch sheet specimens of Cb752, D43 and SU16 columbium-base alloys. The thermodynamic relationships were considered and changes in chemistry, structure and mechanical properties, as a result of annealing in contact with an interstitial sink, were investigated. The influence of thermomechanical processing on stability of Cb alloys, in the presence of an interstitial sink, was investigated. Carbon, oxygen and nitrogen were rapidly withdrawn from Cb-base alloys by Ti alloys. For example, the carbon level in D43 was reduced from 1000 ppm to less than 50 ppm after 20 hrs at 2200F (1200C) in contact with Ti-30V alloy. Complete removal of the structure-stabilizing precipitates occurred and recovery and recrystallization processes took place at temperatures well below the normal recrystallization temperatures for this alloy. An activation energy value for the process of removal of carbon from D43 was established which indicated that diffusion of zirconium from ZrC precipitates into the Cb alloy matrix was rate controlling. Mechanical property tests showed that considerable loss of room and elevated temperature strength resulted from sink-annealing treatments. (Author)

Descriptors :   (*NIOBIUM ALLOYS, DISPERSION HARDENING), HEAT SINKS, REFRACTORY METALS, MECHANICAL PROPERTIES, BRAZING ALLOYS, TITANIUM ALLOYS, FLUID DYNAMICS, ANNEALING, CHEMICAL PROPERTIES, STRUCTURAL PROPERTIES, CRYSTALLIZATION, ZIRCONIUM ALLOYS, COATINGS, SOLID SOLUTIONS, FLEXURAL STRENGTH, TENSILE PROPERTIES, CREEP, ELECTRON MICROSCOPY

Subject Categories : Properties of Metals and Alloys
      Fabrication Metallurgy
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE