摘要
研究了Bridgman定向凝固技术制备的Ni-Si过共晶自生复合材料在不同凝固阶段时的组织特征、相的析出特征以及相组成。探讨了Ni-Si过共晶复合材料的晶体生长机制以及退火温度对亚稳相的影响。结果表明:未定向凝固时的组织呈树枝晶组织,定向凝固初始阶段组织相对粗大,随着热流逐渐趋于稳定,晶体沿最优生长方向生长,组织相对细小且生长稳定。非平衡凝固时Ni-Si过共晶组织包括α-Ni基体相,Ni-Ni_3Si共晶相和Ni_(31)Si_(12)亚稳相,亚稳相Ni_(31)Si_(12)的存在使Ni-Si过共晶合金的硬度增加,脆性增加。1100℃退火保温30 min后得到的显微组织中亚稳相Ni_(31)Si_(12)明显减少。Ni-Si过共晶组织中Ni相为非小平面相,Ni_3Si相和Ni_(31)Si_(12)相为小平面相。
Microstructure,precipitation features of different phases and phase composition of Ni-Si hypereutectic composites prepared by Bridgman directionally solidification technology at different solidification stages were studied.The crystal growth mechanism of the Ni-Si hypereutectic composites and the effect of annealing temperature on metastable phase were analyzed.The results show that the non directional solidification microstructure of the alloy is dendritic crystal,and the microstructure is relatively coarse at initial stage of directional solidification.The crystal growth direction tends to be parallel with the preferred growth direction when the heat flow is table,and the microstructure is refined at the same time.The Ni-Si hypereutectic is composed of α-Ni matrix,Ni-Ni_3 Si eutectic and metastable Ni_（31）Si_（12） phase during non-equilibrium solidification,and the metastable phase Ni_（31）Si_（12） can improve the hardness and brittleness of the NiSi hypereutectic alloy.The amount of the metastable Ni_（31）Si_（12） phase decreases significantly after annealing at 1100 ℃ for 30 min.The Ni phase in the Ni-Si hypereutectic is a non-faceted phase,while the Ni_3 Si and Ni_（31）Si_（12） phases are faceted phase.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2017年第9期11-17,共7页
Transactions of Materials and Heat Treatment
基金
国家自然科学基金(51201121)
2015陕西省留学人员科技活动择优资助项目
陕西省国际科技合作与交流计划项目(2016KW-055)
陕西省耐磨材料工程技术研究中心专项资金项目(2016NMZX03)
关键词
定向凝固
共晶自生复合材料
小平面相
布里奇曼法
directional solidification
eutectic in situ composite
faceted phase
Bridgman method
