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控制铸件的固化和冷却速度会大大影响合金的宏观结构与微观结构及其最终机械特性。根据期望要得到的结果,金属可以极其缓慢地也可几乎瞬时地予以冷却。要制造单晶体,金属得在模具中以每秒10~(-3)～10~(-1)度的冷却速度予以固化。制造出来的铸件与涡轮叶片的实际形状几乎相同。反之,以每秒10~6度的速度快速固化,则得到粉状或带状物。这些材料晶粒极细,并且合金元素和强化相位分布均匀。单晶体超合金作为航天飞机主发动机高压涡轮泵的涡轮叶片正在鉴定之中。虽然这些叶片将在比飞机涡轮低的稳态温度环境中工作,但是它们经受的疲劳状况势必要严重得多。国家航空航天局的刘易斯研究中心和马歇尔研究中心都在研究如何改善超合金的抗疲劳性以及如何更好地了解氢对超合金的有害影响。
Control of casting solidification and cooling rate will greatly affect the alloy’s macrostructure and microstructure and its final mechanical properties. Depending on the desired result, the metal can be cooled very slowly and almost instantaneously. To make a single crystal, the metal is cured in a mold at a cooling rate of 10 -3 to 10 -1 degrees per second. The actual shape of the castings and turbine blades is almost the same. On the contrary, at 10 to 6 degrees per second fast curing, you get a powder or ribbon. These materials are very fine grains, and alloying elements and strengthening the phase distribution. Single-crystal superalloys are being identified as the turbine blades of the high-pressure turbo-pumps of the shuttle’s main engine. Although these blades will operate at a lower steady-state temperature than aircraft turbines, they experience a much weaker fatigue condition. Both the Lewis Research Center and the Marshall Research Center at NASA are investigating how to improve the fatigue resistance of superalloys and how to better understand the harmful effects of hydrogen on superalloys.