During approximately the last ten years, there have been several papers comparing the secondary dendrite arm spacings (lambda2) of alloys processed in microgravity and unit-g environments. To utilize NASA's KC-135 aircraft, which flies a cyclic parabolic route designed to provide periods of high gravity (etwa gleich 10(-3) g for etwa gleich 20 s) alternating with periods of high gravity (etwa gleich 1.8 g for etwa gleich 90 s). Recently, both a superalloy and a Fe-C-Si alloy have been directionally solidified aboard the KC-135, and larger secondary spacings were reported to develop in myg. The high-g/low-g profile is not as sharp and regular as schematically depicted. The analysis further neglects the time necessary to initiate or damp out convection currents when changing gravity levels and does not consider any mechanical effects to which the solid-liquid interface may be subjected during flight and cycling. The factors present further complicating effects, which must be recognized when evaluating the secondary dendrite arm spacings (or other microstructural constituents) from directionally solidified samples processed on the KC-135.
Mixed gravity mode growth during directional dendritic solidification aboard the KC-135
Gemischtes Schwerkraftwachstum waehrend der gerichteten Dendritenerstarrung im KC-135
Metallurgical Transactions A, Physical Metallurgy and Materials Science ; 20A , 7 ; 1284-1286
1989
3 Seiten, 1 Bild, 20 Quellen
Article (Journal)
English
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