Precipitation hardening mechanism

About 70-80% of the embrittlement effect is attributed to the metallic clusters or, more precisely, to the coherent Cu clusters or precipitates. The influence of the Cu clusters and P clusters is attributed to an age or precipitation hardening mechanism. The importance of Ni content in the embrittlement process has become apparent, but the physical role of Ni (dependent on or independent of Cu content) is not well understood. 

Table 3.17 Mechanical properties of typical precipitation hardening and semi-austenitic...

Precipitates have important effects on the mechanical, electronic, and optical properties of solids. Precipitation hardening is an important process used to strengthen metal alloys. In this technique, precipitates are induced to form in the alloy matrix by carefully controlled heat treatment. These precipitates interfere with dislocation movement and have the effect of hardening the alloy significantly. 

The addition of tellurium has a deoxidizing action and confers on lead useful work and precipitation-hardening properties. It also improves resistance to wear, vibration, and mechanical breakdown. These properties, along with improved corrosion resistance, are utilized in the sheathing of power communication and marine cables, in chemical equipment (especially those exposed to sulfuric acid), or where resistance to fatigue is important. Tellurium has successfully replaced tin (1—3% Sn) in the sheathing. Thinner sheaths can be extruded, and the extrusion pressure for 0.05% Te-beafing lead is about the same as for a 3% Sn alloy. 

Our current ambition is to elucidate one of the microscopic mechanisms that has been charged with giving rise to solution and precipitate hardening. The argument is that by virtue of the elastic fields induced by an obstacle there will be a force on a dislocation which the dislocation must overcome in its motion through the crystal. As a first step towards modeling this phenomenon, we imagine the obstacle to be a spherical disturbance within the material. As was already demonstrated in chap. 7, such an obstacle produces spherically symmetric displacement fields of the form Ur = Ar + bjr. ... 

AA. Aluminum Association produced a four-digit system for wrought aluminum alloys and a three-digit system for cast alloys. Examples are alloys 6010 (wrought) and 356 (cast). A temper designation is also required. It follows the alloy designation and indicates the heat-treated or mechanically worked condition of the alloy such as 6010-T6. The T6 suffix indicates the alloy is in the precipitation hardened condition for optimum strength. 

Strengthening Mechanism PH precipitation hardening SH solution hardening CW cold working... 

A. Denquin, D. Allehaux, M. Campagnac, and G. Lapasset, Microstructure and Mechanical Evolutions within Friction Stir Welds of Precipitation Hardened Aluminum Alloys, Mater. Sci. Forum, Vol 426-432, 2003, p 2921-2926... 

Bat] Mechanical testing in an Instron tensile machine at a constant cross-head speed corresponding to a strain rate of 2.8-10 " -s 0.2% PS, YS, precipitation hardening... 

Small amounts of ternary metal phosphides are important for special purposes. Thus, Florenskyite, FeTiP [22], is utilised for precipitation hardening in interstitial-free ferrite steels [23]. Other ternary phosphides with similar (FcjP type) crystal structures (Chapter 8.1), for example, NiCrP, MoNiP and FeNiP can strongly inflnence the microstructure and mechanical properties of glassy metal alloys. 

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