Solution-strengthened alloys

However, it has to be noted here that some solid solution strengthened alloys are supersaturated at room temperature. This is the case, for example, for the alloy AlMg 4.5 Mn. If the material is cooled too slowly... 

Chemistry Ti-6246 is a solid-solution-strengthened alloy end Density that responds to heat treatment as a resiilt of the beta-stabilizing effect of its 6% molybdenum content. Silicon additions (0.08 wt%) improve creep... 

In summary, we have discussed the three mechanisms that may be used to strengthen and harden single-phase metal alloys strengthening by grain size reduction, solid-solution strengthening, and strain hardening. Of course, they may be used in conjunction with one another for example, a solid-solution strengthened alloy may also be strain hardened. 

For nickel, cobalt, and hon-base alloys the amount of solute, particularly tungsten or molybdenum, intentionally added for strengthening by lattice or modulus misfit is generally limited by the instability of the alloy to unwanted CJ-phase formation. However, the Group 5(VB) bcc metals rely on additions of the Group 6(VIB) metals Mo and W for sohd-solution strengthening. 

AH of the alloys Hsted in Tables 4 and 5 are austenitic, ie, fee. Apart from and soHd-solution strengthening, many alloys benefit from the presence of carbides, carbonitrides, and borides. Generally the cubic MC-type monocarbides, which tend to form in the melt, are large and widely spaced, and do not contribute to strengthening. However, the formation, distribution, and soHd-state reactions of carbides are very important because of their role... 

Because pure aluminum is n picaUy too soft to be drawn into a fine wine, it is often alloyed with 1° o sihcon or 1° o magnesium to provide a sofid solution-strengthening mechanism. The resistance of Al-1° o Mg wine to fatigue failure and to degradation of ultimate strength after exposure to elevated temperatures is superior to that of Al—1° o Si wine. 

In addition to these principal alloying elements, which provide soHd solution strengthening and/or precipitation strengthening, wrought alloys may contain small amounts of titanium and boron [7440-42-8J, B, for control of ingot grain size, and ancillary additions of chromium, manganese, and zirconium to provide dispersoids. AH commercial alloys also contain iron and siUcon. 

Table 4. Annealed Tensile Properties of Solution Strengthened Copper Alloys...

Solution hardening is not confined to 5000 series aluminium alloys. The other alloy series all have elements dissolved in solid solution and they are all solution strengthened to some degree. But most aluminium alloys owe their strength to fine precipitates of intermetallic compounds, and solution strengthening is not dominant... 

As we learn from Sims s reviews, many other improvements have been made to superalloys and to their exploitation in recent decades. Solid-solution strengthening, grain-boundary strengthening with carbides and other precipitates, and especially the institution, some twenty years ago, of clean processing which allows the many unwanted impurities to be avoided (Benz 1999) have all improved the alloys to the point where (McLean 1996) the best superalloys now operate successfully at a Kelvin temperature which is as much as 85% of the melting temperature this shows that the prospect of significant further improvement is slight. 

Hafnium is an effective solid solution strengthener at higher temperatures for other alloys such as nickel aluminides (39,40). 

Mickel-llase Superalloys. The nickel-basc superalloys are Ihe most complex in composition and microslrueuirex and. in must respects, the most successful high temperature alloys. The earliest superalloys were wrought, ie fabricated to final size by a mechanical working operation. Later alloys have incorporated higher aluminum plus tilanium contents, as well as molybdenum lor solid-solution strengthening (Nimonics 115 and 1201. 

Apait from y and solid-solution strengthening, many alloys benefit from the presence of carbides, enrhonitrides, ami borides. 

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