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The deformation substructure of TiAl (Llo type ordered lattice) tested in compression, and the factors determining it were investigated. Two types of dislocations take part in the plas-tic deformation, namely a/2 [110] and a/2 [Oil]. The latter type will disorder the Llo super-lattice and therefore would be expected to move in pairs as superdislocations. Some obser-vations are essentially in agreement with the predictions, however the large proportion and morphology of a/2 [O1l] dislocations observed was unexpected. Twins of the [112] (111) type play an important role in the deformation of the alloy, and the early stages of their formation have been recorded. Finally, equi-Schmid factor lines have been constructed in an attempt to evaluate the importance of the sense of the applied stress on the deformation capability of the alloy.

To compare the relative heat sensitivities of human normal and neoplastic cells of the same tissue type, a study was carried out of the relative sensitivities to heat of granulocyte/macrophage progenitor cells (CFU-GM) derived from the peripheral blood and bone marrow of normal subjects and patients with chronic granulocytic leukaemia (CGL). Nucleated haemopoietic cells were incubated at temperatures in the range 41.5 degrees C to 44.0 degrees C for various periods before culture in agar. The results of these experiments showed that CFU-GM from normal blood were consistently less sensitive to damage by heat than normal marrow CFU-GM. There was no comparable difference in the relative heat sensitivities of CFU-GM from blood and marrow of patients with CGL and no significant difference between the heat sensitivities of CFU-GM derived from marrow from normal individuals and patients with CGL. The observed difference in heat sensitivity of CFU-GM from normal blood and marrow accords with other data suggesting that the two progenitor cell compartments are distinct: the blood CFU-GM may represent a more primitive population of committed progenitor cells. In CGL, CFU-GM in the blood may much more closely resemble those in the marrow. The data provide no support for the hypothesis that malignant cells differ intrinsically from their normal counterparts in respect of sensitivity to damage by hyperthermia.

To gain insight into the factors which control the creep-rupture properties of powder metallurgical nickel-base superalloys at intermediate temperatures (650 to 775°C), a comparative study was conducted on the alloys AF115, modified MAR-M432 (B6) and modified IN100 (MERL76). Creep-rupture properties in these alloys were characterized in terms of the stress and temperature dependence of the secondary creep rate, eS, andrupture time,t R . Within the limited stress ranges used, the stress dependence of both eS andt R at 704°C can be represented by power laws eS andC n andt R =Mσ -p ; whereC,M, n, andp are constants. The stress exponentsn andp are approximately equal for both AF115 and B6 with values of 16 and 7, respectively. In the case of MERL76,n andp are different, with values of 15 and 5, respectively. The apparent activation energies,Q, are 700, 370 and 520 KJ mol-1 for AF115, B6 and MERL76, respectively. For these alloys, long creep-rupture lives are associated with large values ofn andQ. The sig-nificant differences inn andQ values between AF115 and B6 were related to creep re-covery processes for which the lattice misfit between the gamma and the gamma prime was identified to be an important parameter. However, the unequaln andp values in MERL76 compared with those in AF115 and B6, were traced to differences in fracture mode. Failures in AF115 and B6 were initiated at carbide particles at grain boundaries. In contrast, fracture in MERL76 was initiated at grain boundary triple junctions. The rupture lives of AF115 and B6 can be modeled reasonably well by the growth of cavities during secondary creep and propagation of a surface-nucleated crack during the tertiary creep.

Turbine disks for gas turbine engines are made from nickel-base superalloys but can be fabricated by several processing methods. The choice of a specific processing route depends on a variety of interrelated factors which include design property requirements, materials selected, and processing costs. It is shown that disk fabrication by direct hot isostatic consolidation of nickel-base superalloy powders, is the most cost-effective method of production; however, such a manufacturing route must yield a product compatible with the property requirements of the component. Some of the metallurgicalfactors that influence such properties in as-hot isostatically pressed (HIP) material are examined. It is shown that by control of the HIP condition, manipulation of composition and heat treatment can be used to control properties. Discussion centres on the balance between strength and stress rupture properties, and resultsfor low-carbon Astroloy and a modified IN 100 alloy, identified in a recent alloy devel...

The U.S. Bureau of Mines development of the Kroll process1 for the production of titanium metal resulted in the general availability of this material by the early 1950’s. Titanium was immediately hailed as the panacea for all structural applications demanding high strength and low density. Today, perhaps, this view could be regarded as somewhat overoptimistic. However, titanium alloys have been used successfully for a number of years in a wide range of industrial applications.

When mouse bone marrow or spleen cells were incubated for 24 hours in medium conditioned by marrow adherent cells, the survival of pluripotent hemopoietic stem cells (CFUs) was considerably greater than that of stem cells incubated in fresh or spleen-conditioned medium. Medium conditioned by endosteal cells also increased marrow CFUs survival. Survival of CFUs more than 24 hours was greater when fresh marrow was incubated directly with marrow adherent cells than with medium conditioned by these cells. Although marrow-conditioned medium greatly increased CFUs susceptibility to 3H-thymidine suicide, DNA synthesis inhibitors did not prevent the increased survival of CUFs in marrow-conditioned medium. These results indicate that marrow stromal cells produce a factor that increases CFUs survival in vitro independently of proliferation.

This program addresses the development of iron aluminide base alloys by rapid solidification and the determination of their potential for use in aircraft turbine engines as alternatives to high chromium steels and nickel-base alloys. The program was divided into three tasks. A process and model development task to define thermomechanical processing requirements for Fe3A1 base alloys, a task to produce and deliver to the Air Force Materials Laboratory a number of alloys produced by the P&W rapidly solidified powder process and a task for the development of austenitic Fe-Mn-A1 alloys with improved elevated temperature properties.

A 2-year program was conducted to explore the potential of NiAl as a high temperature structural material with emphasis on overcoming the low temperature brittleness problem. The inherent ductility characteristics of binary alloys containing 29 a/o Al to 54 a/o Al were studied and it was observed that room temperature ductility was achieved only in alloys with lower amounts of Al. The highest Al level in which room temperature ductility was observed is process dependent, being 35 a/o in the case of the melt spun alloys and 29 a/o for the cast alloys. The brittle to ductile transition temperatures for the higher aluminum alloys (43 a/o - 52 a/o) were found to be in the range 375 c to 625 c, showing no clear trends in terms of the Al content and starting form (castings versus powder). Minor additions of boron significantly raised strength and the brittle to ductile transition temperature. An attempt to improve the ductility of NiAl through modification of the basic deformation behavior was made. Keywords: Nickel aluminide, Ordered alloys, Intermetallic, Ductility, Disk alloys.

Media conditioned by marrow adherent cells from anaemic Sl/Sld and W/Wv mice increased the 24-h survival of CBA CFUs in vitro compared to fresh medium to about the same extent as marrow-conditioned medium from normal Sl+/Sl+, W+/W+, and CBA mice. Sl/Sld marrow-conditioned medium also increased the percentage of CFUs in DNA synthesis to the same extent as CBA marrow-conditioned medium. These results demonstrate that Sl/Sld mice produce a marrow stromal factor that increases both survival of CFUs and the percentage of CFUs in DNA synthesis in vitro. Therefore, the defective haemopoietic microenvironment of Sl/Sld mice is not due to a deficiency in the production of this factor.

Evidence is presented that in human granulocytes the immediate precursor pool of phenylalanine for protein synthesis in vitro is intracellular significant compartmentation.

The martensitic transformation and the effect of cobalt additions on important martensitic toughening parameters are being studied as a means of toughening NiAl alloys. Cobalt additions to NiAl martensite are seen to lower the Ms temperature, reduce the transformation strain anisotropy, and reduce the transformation temperature hysteresis (an indicator of interfacial mobility). Optimization of these parameters should allow martensitic transformation toughening processes to aid in overcoming the ambient temperature brittleness of NiAl alloys.

The U.S. Bureau of Mines development of the Kroll process1 for the production of titanium metal resulted in the general availability of this material by the early 1950’s. Titanium was immediately hailed as the panacea for all structural applications demanding high strength and low density. Today, perhaps, this view could be regarded as somewhat overoptimistic. However, titanium alloys have been used successfully for a number of years in a wide range of industrial applications.

1. The metabolism of the anticonvulsant oxadiazole, Ro 03-4066, was investigated in three human volunteers. Following oral administration 34% of the dose was excreted in urine in six hours.2. The two major urinary metabolites were isolated and identified as derivatives. Their structures indicated that the initial step in the metabolism was hydroxylation of the N-methyl group.3. Some of the N-hydroxymethyl metabolite was conjugated and eliminated in urine and some lost formaldehyde to form the corresponding secondary amide which was further hydroxylated and conjugated before excretion.

To understand the role of cobalt in nickel-base superalloys, multicomponent nickel solid solutions with various amounts of cobalt were studied. Alloys A, B, C and D which contain cobalt at 30, 17, 8 and 0, respectively, and constant concentrations of Cr(25), Mo(5), Al(0.5), Ti(0.5), Nb(0.4), Hf(0.1), all in weight percent, were produced by casting. Compressive creep tests of these alloys were conducted at temperatures between 650°C and 810°C. Table 1 shows the minimum creep rates at 704°C at a stress of 120% of their respective yield strengths. It can be seen that the alloy without cobalt (Alloy D) creeps at a rate 20 times faster than Alloy A with 30 wt.% cobalt and the values for Alloys B and C with intermediate cobalt contents fall between Alloys A and D. Thin foil studies have revealed that the differences can be attributed, in part, to (i) change of stacking fault energy with cobalt, (ii) precipitation of fine gamma prime particles during creep.