Grain refinement in magnesium alloys by aging-rolling-aging method and by rolling in two phase region.

发展了一种制备细晶镁合金的新工艺。剧烈的变形和时效方法可以产生这种材料，但是，例如，ECAP方法，高挤压比挤压或多轴锻造不能应用于大尺寸材料。箔冶金可应用于板材，但不适合连续生产。简单的轧制和时效方法有利于大规模应用和连续生产。该方法的晶粒细化机理是基于动态再结晶，因此首次对高纯镁的再结晶进行了研究。在室温下对厚度约为0.8 mm、大小约为10 x 10 mm^2的纯镁试样进行冷轧，冷轧压下率最高可达80%。透射电子显微镜观察表明，在30%左右冷轧时发生再结晶，而在20%左右冷轧时发生再结晶。 ...更多信息 ut 80%时，试样大面积发生再结晶。伯格斯矢量位错分析表明，非基底滑移系统，即使在室温下运行。镁具有易于再结晶的固有性质。而纯镁的再结晶晶粒会发生晶粒长大，镁化物对晶粒长大有抑制作用。对Mg-Li-Zn合金进行固溶热处理、时效处理，然后在两相区（α+β）进行热轧，使α和β晶粒同时细化。然而，Mg-Li-Zn合金通常不用于工程材料。因此，对AZ 31 B和AZ 91 E镁合金采用相同的轧制和时效工艺。AZ 31 B合金的晶粒尺寸由固溶处理时的50 ~ 100 μm左右减小到3 ~ 5 μm左右。铸态AZ 91 E镁合金的晶粒尺寸由200 μm左右减小到20 μm左右，实现了对工程镁合金的晶粒细化，但织构表现为基面垂直于试样表面，这是镁合金板材的普遍织构。为了实现细晶组织和非基面织构，我们新开发了另一种方法，即将片状试样热压成波浪形，在45度旋转试样的情况下重复压制15至18次。该方法成功地实现了这一目的。少

A new technique for preparing magnesium alloys having fine grained microstructures has been developed. Severe deformation and aging method can lead to such materials, but, for example, ECAP method, extrusion with high extrusion ratios or multi axes forging could not be applied to materials with large scales. Foil metallurgy may be applied to sheet materials, but it is not appropriate for continuous production. Simple rolling and aging method seems to have advantages in large scale application and continuous production. Mechanism of the grain refining in this method is based on dynamic recrystallization.Therefore, recrystallization in high purity magnesium was firstly investigated. Specimens of pure magnesium of about 10 x 10 mm^2 and 0.8 mm in thickness were cold rolled at room temperature with various reduction rates up to 80 %. Transmission electron microscopic(TEM) observations showed that recrystallization occurred in cold-rolled at about 30%, and in the specimen cold-rolled at abo … More ut 80%, recrystallization occurred in a large area of the specimen. Burgers vector analyses of dislocations in the specimen showed that non-basal slip system was operated even at room temperature. Magnesium has an intrinsic property for easily recrystallizing. However, in the case of pure magnesium, grain growth of recrystallized grains occurs.Precipitates were seemed to be effective to suppress the grain growth. Magnesium-lithium-zinc alloys were solution heat treated, aged and then hot-rolled at the temperature range corresponding to two phase (α+β) region, which lead to grain refining in both the α and β grains. However, Mg-Li-Zn alloys are not generally used for engineering materials. Therefore, the same process composed of rolling and aging was applied to AZ31B and AZ91E magnesium alloys. On the AZ31B alloy, grain size was decreased from about 50 to 100 μm in solution heat treated condition to about 3 to 5 μm after the treatment. While on the AZ91E alloy, which was as cast alloy, grain size was decreased from about 200 μm into 20 μm in diameter.Grain refining on engineering Mg alloys was successfully carried out as mentioned above, however, textures of the alloys showed that the basal plane was perpendicular to the specimen surface, the general texture of magnesium alloy sheets. In order to accomplish both the fine-grained microstructures and non-basal textures, we have newly developed another method, that is, the sheet specimen was hot-pressed to be formed a wavy shape, the pressing was repeated with rotating the specimen at 45 degrees for 15 to 18 times. The aim has been successfully achieved by the method. Less