Ductility hardening

Lead—tin (1.8—2.5 wt %) is used both as a cable sheathing ahoy (BS 801 ahoy A and DIN 17640) and as a battery connector ahoy ia sealed lead—calcium—tin batteries (15). Tia is generahy added to lead—arsenic cable ahoys ia smah amounts. The arsenic ahoys have excehent creep resistance and mechanical properties, but are unstable and lose arsenic readily by oxidation. The addition of smah amounts of tin (0.10—0.20 wt %) eliminates arsenic loss. Lead ahoys having 0.4 wt % tin and 0.15 % cadmium, which are used for cable sheathing, do not age harden, show excehent corrosion and creep resistance, and are very ductile. 

Pure metals are very soft indeed, and have a high ductility. This is what, for centuries, has made them so attractive at first for jewellery and weapons, and then for other implements and structures they can be worked to the shape that you want them in furthermore, their ability to work-harden means that, after you have finished, the... 

Austenitic steels have a number of advantages over their ferritic cousins. They are tougher and more ductile. They can be formed more easily by stretching or deep drawing. Because diffusion is slower in f.c.c. iron than in b.c.c. iron, they have better creep properties. And they are non-magnetic, which makes them ideal for instruments like electron microscopes and mass spectrometers. But one drawback is that austenitic steels work harden very rapidly, which makes them rather difficult to machine. 

Figure 3.5. Eflett of temperature on the tensile strength of copper (A) effect of annealing on strength and ductility (B) hardened high-conductivity copper 129. ...

A ductile material can be stretched uniformly only when stable flow occurs. The stable flow of materials has been investigated by Hart who described the transition from the stable to unstable flow. The beginning of geometrical instability and localisation of strain is the limit of the stable flow. At temperatures above 0.5 T (at equilibrium between recovery and hardening) the strain rate sensitivity parameter "m" may be derived from the expression ... 

With the precipitation hardening types, high strengths can be obtained with good toughness. A feature of these steels is that the ductile-brittle transition is less sharp, although low impact values are obtained at very low temperatures. Properties for a typical example are shown in Tables 3.17 and Fig. 3.13. 

All the stainless steels can be machined in the softened states, but they may present some problems unless the correct techniques are adopted. This is especially so with the austenitic grades where the extreme ductility minimises chip breaking and the work hardening may cause difficulties unless modest cuts are made. The free-cutting grades (those with high sulphur contents or selenium additions) are much easier to machine, but it must be remembered that they have somewhat reduced corrosion resistance, ductility and weldability compared to their normal counterparts. Detailed machining instructions are readily available from steel suppliers. 

Niobium is always found in nature associated with tantalum and it closely resembles tantalum in its chemical and mechanical properties. It is a soft ductile metal which, like tantalum, work hardens more slowly than most metals. It will in fact absorb over 90% cold work before annealing becomes necessary, and it is easily formed at room temperature. In addition, welds of high quality can be produced in the metal. In appearance the metal is somewhat similar to stainless steel it has a density slightly higher than stainless steel and a thermal conductivity similar to 1% carbon steel. 

Most structural steels of interest begin to yield at strains of about 0.002 or less. The more ductile steels can undergo fairly large strains beyond this point before the onset of strain hardening. Ultimate strain at rupture of mild steel is typically on the order of 0.20 to 0.25, more than 100 times... 

Reinforced concrete is the most commonly used construction material for structures designed to resist explosive blast loads. It is used extensively in blast hardened structures because of its strength, ductility (when properly designed), mass, penetration resistance, relative economy, and universal availability. Its strength, mass, and ductility provide high resistance to the extreme blast pressure (psi) and impulse (psi-ms) loads. It is important to remember that (unlike in static load design) in the... 

The metals are comparatively soft and ductile impurities generally have hardening and embrittling effects. Notice, as a result of the lanthanide contraction, the nearly equal atomic volumes of Nb and Ta, and the consequent very different values of the densities. 

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