Na LI
,
Zhenyu LIU
,
Yiqing QIU
,
Zhaosen LIN
,
Xianghua LIU
,
Guodong WANG
,
null
,
null
,
null
,
null
,
null
,
null
材料科学技术（英）
In the present paper, low carbon steel strips with different phosphorus contents were produced using a twin roll strip casting process. The solidification structure was studied and its features were analyzed in detail. It was found that the strips possessed a fine microstructure compared with the mould cast steels. With increasing phosphorus content more ferrite has been formed with finer grains.
关键词:
hosphorus
,
Solidification
,
structure
,
Stri
Guanghui MENG
,
Xin LIN
,
Weidong HUANG
材料科学技术（英）
Based on the Jackson and Hunt’s analysis, the selection of lamellar spacing in regular eutectics was reexamined at low velocity. The isothermal assumption was released and the effective interface undercooling was determined by the weighted average of the eutectic phases. It is found that the lamellar spacing minimized the effective interface undercooling depends only on the intrinsic characteristics of a given system at a fixed velocity. In addition, the selection of lamellar spacing is related to the relationship between the average interfacial undercoolings of the eutectic phases and the lamellar spacing. The selected lamellar spacing obviously deviated from that predicted by the Jackson and Hunt’s analysis if the variation of the average interfacial undercoolings of the solid phases with the lamellar spacing was markedly different at a constant growth rate.
关键词:
Solidification
,
null
,
null
,
null
李岩
,
刘泊天
,
张静静
,
高鸿
,
邢焰
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2015.01.010
为满足航天电子产品的工艺实施和空间服役要求,本文详细开展了MD-130胶黏剂的固化工艺及空间适应性研究.结果表明,在150℃等温固化60 min后其拉伸剪切强度达到18 MPa,表明其为优选的固化工艺.高低温环境冲击和低剂量的粒子辐照后胶黏剂固化反应更加充分,其芯片剪切强度提高,而大剂量辐照致使高分子降解现象明显,造成了胶接强度的降低.经环境试验后,MD-130胶黏剂仍具有良好的力学性能,满足设计使用要求.
关键词:
航天器
,
固化
,
力学性能
,
辐照
Jiuzhou ZHAO
,
L.Ratke
,
Jun JIA
,
Qingchun LI
材料科学技术（英）
The microstructure development during a cooling period of alloys being immiscible in the liquid state such as Al-Pb or Al-Bi has gained renewed scientific and technical interest during the last decades. Experiments have been performed to investigate the phase transformation kinetics in the liquid miscibility gap and numerical models have been developed to simulate and analyze the solidification process. The recently developed computational modeling techniques can, to some extent, be applied to describe the decomposition, the spatial phase separation and the microstructure evolution during a cooling period of an immiscible alloy through the miscibility gap. This article overviews the researches in this field.
关键词:
Immiscible alloy
,
null
,
null
,
null
H.Zhang
,
G.Wei
,
L.Zheng
,
L.Li
,
X.Y.Wang
,
A.Vaidya
材料科学技术（英）
A good understanding of melting and resolidification of the substrate will help us to achieve better bonding. A numerical model is developed to investigate the solidification of the droplet, and melting and resolidification of the substrate. The molybdenum powder spraying onto three different substrates: a stainless steel, brass (70%Cu) and aluminum by atmospheric plasma spraying has been investigated. The maximum melting depth of the substrate has been measured and compared with the numerical prediction. Experimental results show that the material properties of the splat and substrate and melting temperature of the substrate play the important roles on substrate melting. A dimensionless parameter, temperature factor, has been proposed and served as an indicator for substrate melting.
关键词:
Thermal spraying
,
null
,
null
,
null
,
null
Andreia Sommerfeld
,
Bernd Bö
,
ttger
,
Babette Tonn
材料科学技术（英）
Microstructure strongly influences the mechanical properties of cast iron. By inoculating the melt with proper inoculants, foreign substrates are brought into the melt and eventually the graphite can crystallize on them. The elements and substrates that really play a role for nucleation are yet unknown. Until now there is very little knowledge about the fundamentals of nucleation, such as composition and morphology of nuclei[1,2]. In this work we utilized EN-GJL-200 as a base material and examined several produced specimens. The specimens were cast with and without inoculants and quenched at different solidification states. Specimens were also examined with a high and low oxygen concentration, but the results showed that different oxygen contents have no influence on the nucleation in cast iron melts. Our research was focused on the microscopic examination and phase-field simulations. For studying the samples we applied different analytical methods, where SEM-EDS, -WDS were proved to be most effective. The simulations were conducted by using the software MICRESS®[3], which is based on a multiphase-field model and has been coupled directly to the TCFE3 thermodynamic database from TCAB. On the basis of the experimental investigations a nucleation mechanism is proposed, which claims MnS precipitates as the preferred site for graphite nucleation. This theory is supported by the results of the phase-field simulations.
关键词:
Graphite nucleation
,
null
,
null
,
null
Hongyang ZHAO
,
Dong-Ying Ju
,
Lin HU
材料科学技术（英）
The twin-roll casting (TC) process of Al alloy was presented. Microstructure and crystallization of the as-cast strip are investigated to link the strip quality and microstructure with the process conditions. The process variables of cooling rate, temperature history and solidification finish point and their influences are discussed. The results revealed the ability of the twin-roll caster to produce directly the thin strip of Al alloy with improved mechanical strength.
关键词:
Twin-roll
,
null
,
null
,
null
M.M.Haque
,
A.A.Khan
材料科学技术（英）
In this work, alpha (α) brass was poured in green sand mould and metallic chill mould at about 1050℃. Sand casting method and metallic chill casting method are representing the slow and fast cooling rates of the castings, respectively. The slow cooling rate in the sand mould produces larger grains, while the metallic chill mould produces smaller grains in the castings. As the grain size decreases, the strength of the cast brass increases; micro-porosity in the casting decreases and the tendency for the casting to fracture during solidification decreases. Thus, the faster cooling rate casting offers higher strength, density and hardness compared to the slow cooling rate casting.
关键词:
Green sand
,
null
,
null
,
null
