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发表于 2023-6-9 12:47:23
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HEAT TREATING AND MECHANICAL PROPERTIES
For most applications, INCONEL alloy 718 is specified as: solution annealed and precipitation hardened (precipitation
hardening, age hardening, and precipitation heat treatment are synonymous terms). Alloy 718 is hardened by the precipitation
of secondary phases (e.g. gamma prime and gamma double-prime) into the metal matrix. The precipitation of these nickel-
(aluminum, titanium, niobium) phases is induced by heat treating in the temperature range of 1100 to 1500°F. For this
metallurgical reaction to properly take place, the aging constituents (aluminum, titanium, niobium) must be in solution
(dissolved in the matrix); if they are precipitated as some other phase or are combined in some other form, they will not
precipitate correctly and the full strength of the alloy with not be realized. To perform this function, the material must first be
solution heat treated (solution annealed is a synonymous term).
Two heat treatments are generally utilized for INCONEL alloy 718:
•Solution anneal at 1700-1850°F followed by rapid cooling, usually in water, plus precipitation hardening at 1325°F for 8
hours, furnace cool to 1150°F, hold at 1150°F for a total aging time of 18 hours, followed by air cooling.
•Solution anneal at 1900-1950°F followed by rapid cooling, usually in water, plus precipitation hardening at 1400°F for 10
hours, furnace cool to 1200°F, hold at 1200°F for a total aging time of 20 hours, followed by air cooling.
If the material is to be machined, formed, or welded, it typically is purchased in the mill annealed or stress relieved
condition. The material is then fabricated in its most malleable condition. After fabrication, it can be heat treated as required
per the applicable specification. |
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