杨长林
,
杨根仓
,
刘峰
,
周尧和
金属学报
通过真空熔炼和气体保护, 采用熔融玻璃与循环过热相结合的深过冷快速凝固技术,研究了影响富Fe端Fe-B共晶合金熔体净化效果的主要因素, 确定了该合金熔体获得超过冷的净化方法, 并使Fe83B17共晶合金熔体稳定获得了300-460 K的超过冷度, 使Fe80B20过共晶合 金熔体的过冷度达到了485 K, 从而使Fe-B共晶系合金熔体开始形核前的初始过冷度达到了0.3m-0.4m的水平. 通过对冷却曲线的分析, 讨论了表征超过冷快速凝固的热力学特征.
关键词:
玻璃净化
,
hypercooling
,
undercooling
,
Fe-B eutectic alloy
WEI Bingbo YANG Gencang ZHOU Yaohe Northwestern Polytechnical University
,
Xi'an
,
China
金属学报(英文版)
Undercoolings up to 397 K(0.283 T_E)have been obtained for Ni-32.5% Sn eutectic alloy melted by superheating-cooling cycles and denucleating with inorganic glasses.The predomi- nant dissipation of heat for highly undercooled alloy melt is through radiation.An approxi- mate method is consequently derived to calculate its mean specific heat from measured cooling curves.With the aid of high speed cinematography,it is revealed that the surface or interface heterogeneous nucleation takes place in preference to homogeneous nucleation even though the undercooling has exceeded 0.2 T_E.
关键词:
undercooling
,
null
,
null
,
null
,
null
M. J Li
,
G.S. Song
,
G.C. Yang and YH Zhou (State Key Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
Fe-30at.%Co alloy is undereooled to investigate the effct of remelting on the grain size at certain undereooling rnnges. At low undereoolings, the primary stable fcc phase is remelted, which results in the equiaxed grains. When the melt is undercooled greater than the critical undereooling △T=204K the primary metastable bcc phase will alternatively nucleate in the melt. The primary bcc dendrite will be remelted into isolated dendrite cores dispersing in the remaining liquids. In the meanwhile, the isolated dendrite cores are remelted more or less due to the temperature fluctuation in the liquids. Different crystal structures between bcc and fcc phase make the subsequent crystal growth of fcc phase onto the Primary bcc phase non-epitaxial when the melt is undereooled greater than △T=204K. The primary metastable bcc phase may play an important role in coarsening grains in the systetn at larpe undereoolings.
关键词:
undercooling
,
null
,
null
,
null
张长青
,
姚可夫
金属学报
采用玻璃融覆法(fluxing)提纯技术能显著提高Fe40Ni40P14B6合金的过冷度, 并可获得深过冷条件下的凝固组织. 研究结果表明, 不同过冷度下Fe40Ni40P14B6的凝固组织存在显著差异, 增加过冷度能大幅细化凝固组织. 在深过冷条件下, 能获得纳米晶凝固组织; 当过冷度为360 K时, 所制备的Fe40Ni40P14B6块体纳米晶合金的平均晶粒尺寸约为40 nm; 当过冷度足够大时, 获得的凝固组织具有液相Spinodal分解导致的网状组织特征. 热力学分析结果表明, Spinodal分解所形成的网状组织的特征尺寸与熔体过冷度有关, 过冷度越大, 尺寸越小.
关键词:
Fe-Ni-P-B合金
,
spinodal decomposition
,
undercooling
Wenjing Yao
材料科学技术（英文）
The liquid-solid transitions of (Co2Si+CoSi) and (CoSi+CoSi2) eutectic alloys were realized in drop tube and the rapid eutectic growth mechanism of intermetallic compounds was examined. The experimental and calculated results indicate that with increasing Co content, the intermetallic compound prefers nucleating primarily. The eutectic microstructures experience the transitions of `lamellar-anomalous-divorced' eutectic with undercooling. In undercooled state, the growth of CoSi intermetallic compound always lags behind others, and no matter how large the undercooling is, this intermetallic compound grows under the solutal diffusion control. The calculated coupled zone demonstrates that (Co2Si+CoSi) eutectic can form within certain undercooling regime, when the composition is in the range from 23.6% to 25.4% Si. And the calculated coupled zone of (CoSi+CoSi2) covers a composition range from 40.8% to 43.8% Si.
关键词:
Liquid-solid transition
W.Q.Zhang
,
L.Xiao
金属学报(英文版)
A numerical model is established to simulate the concentration field in irregular lamel-lar eutectic of Al-Si system.Both the undercooling and spacing are dependent on thegrowth rate and the temperature gradient,and increasing growth rate causes an in-crease of undercooling but a decrease of lamellar spacing,while increasing temperaturegradient leads to a decrease of lamellar spacing.The computed results are in goodagreement with experimental observations.
关键词:
irregular eutectic
,
null
,
null
,
null
