Precipitation hardening

Japanese: 析出硬化 - せきしゅつこうか（英語表記）precipitation hardening

When a supersaturated solid solution is aged, it undergoes phase decomposition. At this time, the precipitated phase disperses uniformly and finely in the solid, increasing the hardness of the alloy. This is called precipitation hardening. It can be considered a type of age hardening, but differs in that the effect appears in a short time. It is seen in cobalt-based and nickel-based heat-resistant alloys, heat-resistant steels, some stainless steels, tool steels, high-speed steels, and magnet steels. In these cases, precipitation hardening works effectively, but the temper embrittlement that often occurs in chromium steels and the self-annealing effect of aluminum bronze are examples of cases where precipitation hardening works poorly. The precipitates that contribute to hardening are various, such as metal carbides, nitrides, borides, intermetallic compounds, and GP bands seen in aluminum alloys. Strain aging that appears in low-alloy steels and carbon steels is thought to be a phenomenon that occurs when atoms such as carbon, nitrogen, and oxygen gather at dislocations that increase due to processing, and can also be seen as a type of precipitation hardening.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

過飽和状態の固溶体を時効すると，固溶体は相分解する。このとき，析出相が固体内に均一微細に分散することによって，合金の硬度が上昇する。これを析出硬化という。一種の時効硬化といえるが，効果が短時間で現れる点が異なる。コバルト基，ニッケル基の耐熱合金，耐熱鋼，一部のステンレス鋼，工具鋼，高速度鋼，磁石鋼などにみられる。これらの場合析出硬化は有効に働くが，クロム鋼にしばしば起る焼戻し脆性，アルミ青銅の自己焼鈍効果などは析出硬化が悪く働く例である。硬化に寄与する析出物は金属炭化物，窒化物，ホウ化物，あるいは金属間化合物，アルミニウム合金にみられるG-P帯など，さまざまである。低合金鋼や炭素鋼に現れるひずみ時効は，加工により転位が増殖してその部分に炭素，窒素，酸素などの原子が集るために起る現象と考えられ，やはり一種の析出硬化とみることができる。

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