30 Containment systems Ductility

Tantalum-Titanium Bishop examined the corrosion resistance of this alloy system in hydrochloric, sulphuric, phosphoric and oxalic acids and found that alloys containing up to about 50% titanium retained much of the superlative corrosion resistance of tantalum. Under more severe conditions, a titanium content of below 30% appears advisable from the standpoint of both corrosion resistance and hydrogen embrittlement, although contacting or alloying the material with noble metals greatly decreases the latter type of attack. Tantalum-titanium alloys cost less than tantalum because titanium is much cheaper than tantalum, and because the alloys are appreciably lower in density. These alloys are amenable to hot and cold work and appear to have sufficient ductility to allow fabrication. 

The results indicate that the system containing ETPI has higher compressive yield stress and greater stiffness resulting in greater toughness as shown by the ductility factor. It was concluded that... 

The descriptions presented in the foregoing sections are concerned mainly with composites containing brittle fibers and brittle matrices. If the composite contains ductile fibers or matrix material, the work of plastic deformation of the composite constituents must also be taken into account in the total fracture toughness equation. If a composite contains a brittle matrix reinforced with ductile libers, such as steel wire-cement matrix systems, the fracture toughness of the composite is derived significantly from the work done in plastically shearing the fiber as it is extracted from the cracked matrix. The work done due to the plastic flow of fiber over a distance on either side of the matrix fracture plane, which is of the order of the fiber diameter d, is given by (Tetelman, 1969)... 

Physical Properties. Hafnium is a hard, heavy, somewhat ductile metal having an appearance slightly darker than that of stainless steel. The color of hafnium sponge metal is a dull powder gray. Physical properties of hafnium are summarized in Table 1. These data are for commercially pure hafnium which may contain from 0.2 to 3% zirconium. Although a number of radioactive isotopes have been artificially produced, naturally occurring hafnium consists of six stable isotopes (Table 2). Hafnium crystallizes in a body-centered cubic system which transforms to a hexagonal close-packed system below 2033 K. 

Of the 12 slip systems possessed by the CCP stmcture, five are independent, which satisfies the von Mises criterion. For this reason, and because of the multitude of active slip systems in polycrystalline CCP metals, they are the most ductile. Hexagonal close-packed metals contain just one close-packed layer, the (0 0 0 1) basal plane, and three distinct close-packed directions in this plane [I I 2 0], [2 I I 0], [I 2 I 0] as shown in Figure lO.Vh. Thus, there are only three easy glide primary slip systems in HCP metals, and only two of these are independent. Hence, HCP metals tend to have low... 

In 1986, the presence of superconductivity was observed in a metal oxide system (see Electronic Structure of Solids). This ceramic was brittle, not ductile as for metallic samples. Chemical Vapor Deposition is one method for preparing metal oxide compositions. All presently known superconducting metal oxide compositions contain a group 2 element (Figure 7). Owing to the importance of this area to the future development of the inorganic chemistry of the group 2 elements, it is covered in the present context. 

The mechanical behavior of Zr02-Ni system strongly depends on constitutional variation. The Ni-rich materials exhibit typical behavior of elasto-plastic deformation and ductile fracture similar to metallic material. The materials containing PSZ from 40-80 vol% mainly presents typically linear elastic behavior and macroscopic brittle fracture. However, the material with 60 vol% PSZ behaves as non-linear elastic behavior after the linear stage. 

The development of direction given above is the elaboration of cast eutectic alloys in the system A1 - Ti - Cr, containing Ll2 phase. These alloys have higher melting point (1275 °C), essential ductility in compression tests and high hardness and strength up to 800 °C [28, 29],... 

Only limited studies have been carried out to systematically investigate the mechanical behavior of these materials. Comprehensive data on compositionprocessing-microstructure property relations are lacking due to difficulty in processing these brittle/ductile multiphase systems. In general, well processed alloys containing controlled microstructures are not available. 

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