触变成形ZA27合金的微观组织  

Microstructure Characteristic of Thixoformed ZA27 Alloy

作　　者：赵海静[1] 陈体军[1] 郝远[1] 李向威[1] 张大华[1] 

机构地区：[1]兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,甘肃兰州730050

出　　处：《铸造技术》2010年第8期1029-1033,共5页Foundry Technology

摘　　要：通过OM、SEM和XRD对触变成形并经5年自然时效的ZA27合金的微观组织进行了观察。结果表明:经触变成形后的ZA27合金由球状初生粒子α′相、晶间的二次凝固组织及半固态成形时没有凝固完全的小液池组成。共晶方式主要为离异共晶及其中"蜂窝"状棒状共晶,部分区域出现不规则层片共晶。ZA27合金在后期的冷却和自然时效过程中,经过了一系列的相变,β相发生胞状分解,形成规则的共析α+η层片组织或不规则的复杂形状组织,从一些层片区域逐渐向低铝的α′相区域中心生长为粗大的层片组织,当其生长被α′中心的连续分解所阻挡时,在其芯部形成细小的α+η颗粒组织。The microstructure of thixoformed ZA27 was examined by optical microscope, scanning electron microscope and X-ray diffraction after ageing for 5 years at ambient temperatures. The result indicated that the microstructure compose of nearly globular primary α＇ phase, secondary solidification structure inner or outer primary grains and the liquid does not freeze completely during semi-solid forming. Eutectic models dominate in divorced eutectic and rod-like eutectic in shape of honeycomb. In some regions appeared the irregular lamellar eutectic. On cooling after casting and on natural aging, both of the β phases decompose eutectoidally into well-formed lamellae a and β or irregularly complex structures, and some lamellar colonies spread into the Iow-aluminium α＇-phase cores of the microstructure to form coarse lamellar products. But the growth of these lamellae is always retarded by the continuous decomposition of the α＇ phase in the dendritic cores and they decompose into mixture of fine zinc-rich η phase in an aluminum matrix.

关 键 词：ZA27合金 触变成形 自然时效 微观组织 

分 类 号：TG146.13[一般工业技术—材料科学与工程]