摘要
采用金相显微镜及扫描电镜对VAR法制备V-5Cr-5Ti合金样品进行显微组织观察。观察分析了V-5Cr-5Ti合金铸锭、均匀化热处理、塑性变形及再结晶热处理对合金显微组织的影响,特别对合金中生成第二相的演变规律进行了研究。研究发现,V-5Cr-5Ti合金铸锭中的第二相为薄片状,紧密排列呈不规则曲线。铸态第二相具有热稳定的相结构,其分布与合金基体存在一定的择优取向,通过片状第二相之间的取向关系表现出来。1100℃保温2 h均匀化热处理后,第二相的数量和分布发生变化,但不能完全消除。加工过程中合金表现出良好的可加工性能,第二相的偏聚导致合金硬化区的存在,不利于合金的均匀变形,加大变形量(>60%)有助于消除这一影响。变形过程中第二相不发生弹/塑性变形,变形量较大(>80%)时发生破碎,形成细小的颗粒状第二相。变形合金经过800℃保温1 h处理后组织中出现了再结晶的形核,1000℃保温1 h处理后基体中发现了晶粒的长大。第二相的存在提高了合金的再结晶能垒,使其分布区域的再结晶过程滞后于合金基体,导致细晶带的产生,有利于合金的高温力学性能。
V-SCr-STi alloy ingot was made by VAR method. Samples were taken after uniform heat treated, followed by cold working and recrystallizing heat treatment. OM and SEM were used to study the microstructure of the treated alloy. Precipitates evolution during the processes was studied especially. The results showed that the precipitates, which existed one close another and made up fortuitous lines in the ingot, appeared to be plates. The plates had a certain phase structure with thermal stability, and had a certain orientation relationship to the base metal, which expressed by the orientation relationship among the plates. Uniform heat treatment had a single effect to the number and distribution of the plates while the plates could not be extinguished. The alloy showed well plastic property during cold working. There were hard areas, where precipitates gathered and blocked the deformation uniformity, existed when the deformation rate was low. To increase the deformation rate could cancel the hard areas（ 〉 60% ）. The precipitates, which could never be deformed while cold working, broke to fine grains with the increase of deformation rate（ 〉 80% ）. Nucleation was discovered in the mi- crostructure of deformed alloy treated with a 800 ℃ heat treatment for an hour, while grains growth were found at 1000 ℃. The precipitates increased the energy barrier of recrystallization, blocked the recrystallization, and leaded to a team formation of fine grain bands, which would benefit the mechanical behavior of the alloy under high temperature.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2012年第6期864-869,共6页
Chinese Journal of Rare Metals
基金
国家科技部863计划资助项目(2006AA03A220)
关键词
显微组织
第二相
位错
亚稳态
microstructure
precipitate
dislocation
metastable state
