Studies on the effects of heat-treating and testing environments for the refractory metals have been limited primarily to the unalloyed metals and a few alloys of columbium and molybdenum. Most of this work has relied on compositional changes as a means of assesing the effects of various environments on these materials. It has been shown that all of these materials are subject to contamination or purification in various test environments. The residual gases H2, CO(or N2), and H20, constitute the major sources of contamination when testing columbium and tantalum materials in vacua. Under the same conditions, molybdenum and molybdenum alloys containing carbon and reactive-metal additions are subject to serious decarburization. Nonreactive gaseous atmospheres also cause serious changes in material chemistry, since small quantities of noxious gases are contained in the atmosphere. Several promising methods of circumventing material chemistry changes during various longtime, high-temperature exposures are being used and/or evaluated. (Author).

THE ACHIEVEMENT AND MAINTENANCE OF DESIRED DIMENSIONS IN COMPLEX, PRECISION-BUILT STRUCTURES, SUCH AS ROCKET-MOTOR CASES, ARE CRITICAL AND TECHNICALLY INVOLVED PROBLEMS. Their proper functioning demands close dimensional tolerances. Dimensional stability is extremely difficult toACHIEVE IN STEELS AT ULTRAHIGH STRENGTH LEVELS. The problem stems from interacting metallurgical factors which manifest themselves in volumetric and shape changes. The principal sources of size change are the changes in specific volume accompanying the phase transformations which occur in hardening and tempering. Distortion occurs when a part deforms in response to stress. The problem of dimensional instability is analyzed, the factors involved are discussed, and recommendations are made regarding the control of these factors. (Author).

Premium-quality castings are those which are guaranteed to show a specified high level of mechanical properties. The properties currently being achieved represent significant improvements over those which can be achieved in conventional aluminum-alloy castings and approach the properties currently obtainable in wrought aluminum alloys. These property advances are largely the result of improved casting technique and design. These castings are gradually finding acceptance and usage in aerospace applications, thanks to integrated efforts between the casting producers and their customers. (Author).

This report presents information dealing with the oxidation of nickel- and cobalt-base superalloys. All of the superalloys will oxidize at high temperatures when oxygen is present in the enveloping atmosphere. The rate of oxidation depends upon alloy composition, temperature, oxygen concentration, oxides formed, diffusion rates of the metals in both base metal and oxide, diffusion rate of oxygen in the oxide, solubility of oxygen in the matrix, and a host of other variables. The effects of oxidation can be beneficial or they can be harmful. The first section of this report deals with the fundamentals of the oxidation of Ni-Cr and Co-Cr alloys. Subsequent sections discuss general surface oxidation, intergranular oxidation, other subsurface oxidation, and the effect of stress on the rate of oxidation. Numerous specific alloys are mentioned in the report; as an aid to the reader, the appendix contains an alloy index of the alloys mentioned in the report along with the compositions of the alloys, and the pages on which mention of the alloys is made.

This report is the third of a series which will periodically summarize the status of the various contracts involved in the Department of Defense Refractory Metals Sheet Rolling Program. Under this program, selected candidate materials are being carried through one or more of the following consecutive phases: Phase I, development of a sheet-production practice; Phase II, establishment of minimum design data; and Phase III, evaluation of sheetfabrication characteristics. To the present time, 13 contracts have been funded or planned in support of the Phase I, II, and III activities. This report summarizes the status of each of these individual contracts as of November 1, 1964. The first section describes the overall program of the Department of Defense Refractory Metals Sheet Rolling Program. Following, in the order of their discussions, are sections dealing with fabricable molybdenum alloys, unalloyed tungsten, columbium alloys, and tantalum alloys. (Author).