快速凝固Al—Cr合金的组织和性能

THE MICROSTRUCTURE AND PROPERTY OF RAPIDLY SOLIDIFIED BINARY Al-Cr ALLOYS

在真空单辊急冷装置上制取含Ｃｒ２－１０ｗｔ－％的五种Ａｌ－Ｃｒ合金薄带利用ＸＲＤ，ＴＥＭ，电子探针及能谱分析研究了它们的相组成及显微组织，还测定了显微硬度和抗拉强度．实验表明Ａｌ－８．０Ｃｒ具有较高的显微硬度和最高的强度极限．

Some strips of five Al- (2-10) Wt-% Cr alloys were made on the rapid cooling apparatus with a monoroller.The calculated average cooling rate was about 3-4 x 105℃ / s.The microstructure and the phase consistance of the alloy were studied by XRD, TEM, electron probe and energy spectrum.It was found that in the rapidly solidified alloys, besides the super saturated solid solution α- Al, Al7Cr and Al4Cr phase were formed.In the low Cr content (Cr<4%) alloys, the microstructure all through the thickness of the strips was mainly cell-like supersatured α-Al phase.As the thickness increased , a small amount of secondary phases appeared .In the high Cr content alloys (Cr> 6% ), various microstructures were formed at different locations. In the bottom areas (close to the roller), the microstructure was still cell-like.When the Cr content increased, some secondary phases distributed discontinuously at grain boundary, the amount of these phases inside the grains were also increased. In the center of the strips, foe cell-like structure disappeared, some spherulites which were composed of secondary phases, embeded in aluminium matrix.The spherulites were multi- phase structure, they were generally composed of a core surrounded by small petal-like crystals, the composition of the core and petal-like crystal was close to each other (that's 22 ±3wt-%Cr) .At the top of the strip, the spheruliter showed a kind of spoke-like shape.lt was found that the microstructure of the rapidly solidified alloys were determined by the cooling rate and the amount of alloying elements added. The strength and the microhardness were found to be increased as the Cr content increased.The maximum strength was gained when the Cr content was 8wt-%.This behaviour was associated with the size and volume fraction of the spherulites .It can be said that the Al-8wt-%Cr alloy is a perspective high temperature alloy owing to their high tensile strength (σb= 350MPa) and microhardness (Hv= 1250MPa). Correspondent: Mi Guofa, P.O. Box 434, Harbin Institute of Technology, Harbin 150006