Al-Zn-Cu系室温相图低Cu区的研究

PHASE DIAGRAM OF Al-Zn-Cu SYSTEM IN LOW COPPER SIDE AT ROOM TEMPERATURE

熔制了14个不同成分的Al-Zn-Cu合金,并进行了组织均匀化和平衡冷却至室温的处理.通过显微组织观察、 X射线衍射分析和电子探针微区成分分析,测定了这14个合金的相组成及成分,还通过晶格常数变化和溶质浓度关系的分析,对α与CuZn4相的成分进行了计算,并绘制出了Al-Zn-Cu系低Cu侧的室温相图.结果表明:在室温下Al-Zn-Cu系中存在稳定的化合物T’相,实际确定的室温三相区是: T’+α+β,T’+α+Al2Cu,T’+CuZn4+β,T’+AlCu+Al2Cu.明确了CuZn4中的最高Al含量远远小于原来认知的数值(18％),应该小于7％.

The phase composition and constituent of 14 designed alloys in Al-Zn-Cu system were analyzed by optical microscope, X-ray diffraction and EPMA method. These samples have been made through sufficient uniformization and equilibrium cooling treatment from 400 V to room temperature. Furthermore, the compositions of alpha and CuZn4 phase have been calculated in response to the relation of solute concentration and interplanar distance. Based on these, the isothermal diagram of Al-Zn-Cu system at room temperature has been drawn in lower Cu side from Al4Cu9-Cu5Zn8 compounds to Al-Zn side. The results show that there is stable T' phase in this system. Three-phase equilibrium around T' phase are T' +alpha+beta, T'+alpha+Al2Cu, T'+CuZn4+beta and T'+AlCu+Al2Cu at room temperature. The contents of Al in CuZn4 phase is less than 7%, which is much lower than that to be well known (18%).