摘要
采用单辊实验技术研究了AZ91D镁合金的急冷快速凝固特征。合金条带的凝固组织沿厚度方向分为3个晶区:近辊面细晶区、内部柱状晶区和自由面等轴晶区。XRD分析表明,在快速凝固条件下,L→α Mg+β Mg17Al12的共晶反应受到抑制,条带凝固组织由过饱和的单相α Mg固溶体组成。TEM分析发现,α Mg晶内和晶界上离散分布着的少量Mg17Al12质点,系α Mg固溶体在连续冷却过程中脱溶析出的产物;α Mg中存在着大量的位错线和位错胞。随着辊速增大,晶粒更加细化,柱状晶区减小,位错密度增大,条带强度增加,塑性降低,电阻率增大。
The ribbons of melt-spun AZ91D magnesium alloy with thickness of 4070 μm and length of 80100 mm were obtained by a single roller apparatus. According to the grain morphology, the rapid solidification microstructure of melt-spun magnesium alloy is roughly subdivided into three crystal zones through the thickness section: the fine equiaxed zone near the roller surface, the inner columnar zone and the outer equiaxed zone near the free surface. The X-ray analysis results indicate that the microstructure of the alloy is composed of the single phase α -Mg supersaturated solid solution and the eutectic reaction of L→α -Mg+β -Mg_(17)Al_(12) is suppressed due to rapid solidification. TEM analysis reveals that a little amount of β -Mg_(17)Al_(12) compound, which disperses inside the α -Mg grains and locates at the grain boundaries, is the product of precipitation from supersaturated α -Mg solid solution during cooling processes. Lots of dislocations and dislocation cells exist in α -Mg grains. With the increasing of roller velocity, the α -Mg grains become gradually finer and the inner columnar zone tends to elimination, and the density of dislocation inside the grains increases, and hence the strength and electrical resistivity of the alloy increase remarkably, while the elongation of the alloy decreases.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2004年第6期939-944,共6页
The Chinese Journal of Nonferrous Metals
关键词
镁合金
快速凝固
晶体生长
组织与性能
magnesium alloy
rapid solidification
crystal growth
microstructures and properties
