郑建邦
,
丁浩
,
郭益平
,
刘林
,
柳伟
,
李行健
金属学报
选用K4169Fe—Ni基高温合金，研究了向熔体中加入NixAlyTiz金属间化合物对合金冷凝后的晶粒尺寸、枝晶组织等凝固组织特征的影响结果表明，加入微量NixAlyTiz细化剂并控制合金液的均匀化处理过程可显著细化晶粒，将铸件整体晶粒细化至0、1—02mm；达到ASTM1—3级,同时、枝晶组织出现了由树枝晶向胞状晶的转变、并且NixAlyTiz细化剂的加入对合金的结晶特性及凝固组织无不良影响.
关键词:
Fe－Ni
,
grain refinement
,
nucleant
,
dendrite morphology
,
null
H.C. Liao M. Zhang J.J. Bi K. Ding X. Xi S.Q. Wu
材料科学技术（英文）
Eutectic solidification in near-eutectic Al-13 wt pct Si casting alloys and the effect of trace addition of boron or strontium on it have been investigated using thermal analysis and microstructural characterization. In unmodified alloy, dual eutectic structure has been observed. The coarse eutectic (dendrite-like Al+ coarse Si flakes) is formed above the equilibrium temperature of eutectic (Al+Si) reaction (577°C). The coarse eutectic (CE) grains nucleate from the primary silicon particles formed earlier due to local enrichment of silicon solute and grow in a divorced mode between the dendritic Al phase and large silicon flakes. The fine eutectic (FE) grains nucleate later on other potential sites activated by melt undercooling and grow in coupled-growing mode with the silicon crystals as fine flakes. The formation of the FE grains is favored in the alloys containing boron because of a great number of potential nucleation sites being added from boron-containing particles. Addition of strontium to the alloys restrains completely the formation of primary silicon particles and hence limits the nucleation of the CE. This is because the eutectic point has moved far enough to make the alloy, at this composition (Al-13 wt pct Si), hypo-eutectic. Local cooling rate during solidification has an important influence on competition formation of these two eutectics.
关键词:
Al-Si alloy
,
eutectic
,
solidification
,
dual eutectic grains
,
grain refinement
张秀妹
,
彭开萍
材料热处理学报
对具有不同层错能的材料:Q235钢、纯铜和H62黄铜分别进行模压形变试验,并对其模压形变后的显微组织和力学性能进行研究.结果表明:模压形变可以有效地细化材料的晶粒尺寸;金属材料的层错能越低,晶粒细化效果越好;随着模压道次的增加材料的显微硬度升高;层错能低的H62黄铜,随形变道次增大硬度增加幅度更高.中高层错能的纯铜和Q235钢主要以位错机制细化晶粒,低层错能的H62黄铜主要以位错机制和孪生方式共同作用使晶粒细化.
关键词:
模压形变
,
大塑性变形
,
晶粒细化
,
Q235钢
,
纯铜
,
H62黄铜
,
层错能
X.F. Liu
,
X.F. Bian
,
X.G. Qi
,
M. Thompson and J.J Ma (Colledge of Materials Science and Engineering
,
Shandong University of Technology
,
Jinan 250061
,
China)
金属学报(英文版)
Nucleation sites of α-Al grains after addition of an Al-Ti-B master alloy into pure aluminium have been investigated using EPMA. The results show that either TiAl3 or boride particales can nucleate α-Al grains. But the number of TiAl3 nucleants is reduced with the holding time prolonged and the boride-nuclei are increasing gradually. Based on these results, a new refining method, adding molten Al-Ti-B into commercially pure aluminium, which has a quicker and better refining efficiency is presented.
关键词:
Al-Ti-B master alloy
,
null
,
null
,
null
H. R. Hou
,
Q. Y. Liu
,
Q. A. Chen and H. Dong Division of Structural Materials
,
Central Iron & Steel Research Institute
,
Beijing 100081
,
China
金属学报(英文版)
Heavy deformation and controlled cooling is one of the most effective effective ways for grain refinement in HSIA steels. In this paper, experimental specimens are prepared with a commercial linepipe steel grade X65, and the chemical compositions are (wt% ): Fe-0.094C-1.42Mn-0. 29Si-0. 045Nb-0. 008Ti. After heavy deformation with 80% reduction in non-recrystallization range of austenite, and at controlled cooling rates from 2K/s to 64K/s, the grain sizes vary from 9.55μm to 1.06μm.It is shown by the results that a linear relationship still remains between the yield strength and reciprocal of square root of ferrite grain size as grain size is refined to 1m.The ultra-fine grains might be dynam- ically formed through the deformation-induced transformation when reduction is large enough.The grain sizes decrease when the cooling rates increase.When the cooling rates increase over 10K/s, the grain sizes are rarely changed. The particles distribute on grain boundaries, sub-grain boundaries, deformed bands and within the ferrite grains.
关键词:
microalloyed steel
,
null
,
null
,
null
G.S. Song
,
Z.Z. Zhang
,
X.B. Dong
,
G.C. Yang and Y.H. Zhou(State Key Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
Undereooling eoperiments on binary Ni50 Cu50 alloy melts were conducted. The hypercooling limit of this alloy, which is about 310K, was evaluated by mcasuring plateau time needed for the interkendritic liquid solidification and extmpolating this function to zero. This limit was exceeded first in the binary alloy undereooled by about 320K.The effect of liquid undercooling on the respective microstructure evolution was studied by optical metallogrnphy. The hypercooled microstructure contains rcsidual fragments within grain boundaries and is quite different from those obtained at undercoolings below 310K. The finding indicated the existence of dendrite break up. The dendrite break up may be induced either by remelting or by stress. By considering hyperrooling conditions and comparing two grain ndnement microstructures observed at small and larpe undereoolings, the forms of dendrite break up and the grain refinement mechanism exceeding the hypereooling limit are further discussed.
关键词:
hypercooling
,
null
,
null
,
null
王恒辉
,
万响亮
,
李光强
,
王红鸿
,
吴开明
材料热处理学报
采用金属包埋切片微米-纳米表征法和电子背散射衍射技术分别研究了焊缝金属中针状铁素体形核夹杂和联锁组织特征.结果表明,由于Mn元素扩散到夹杂物内部使得周围形成贫Mn区,诱发针状铁素体在复合夹杂物上形核.同时针状铁素体还可以在已经形成的铁素体表面激发形核;铁素体生长过程中同原奥氏体保持固定取向关系;铁素体相互之间发生硬碰撞和交错现象;这些因素共同形成针状铁素体联锁组织.这种细小有效晶粒尺寸的针状铁素体联锁组织具有良好的强韧性匹配.
关键词:
焊缝
,
针状铁索体
,
力学性能
,
晶粒细化
,
电子背散射衍射
王顺成
,
甘春雷
,
黎小辉
,
郑开宏
,
戚文军
稀有金属材料与工程
采用K2ZrF4、KBF4混合粉末与铝熔体原位合成方法制备了Al-4.99Zr-1.1B合金,利用X射线衍射仪、光学显微镜和扫描电镜,研究了Al-4.99Zr-1.1B合金的显微组织及其对AZ31镁合金的晶粒细化作用.结果表明:Al-4.99Zr-1.1B合金中含有大量细小的ZrB2粒子.随着Al-4.99Zr-1.1B合金添加量的增加,AZ31镁合金的a-Mg晶粒逐渐细化,晶间β-Mg17Al12相从网状转变成细小块状.添加0.6％的Al-4.99Zr-1.1B合金,可使AZ31镁合金的a-Mg晶粒从170 μm细化到45 μm.ZrB2粒子作为a-Mg晶粒的异质形核核心使a-Mg晶粒得到细化.
关键词:
Al-Zr-B合金
,
AZ31镁合金
,
晶粒细化
,
异质形核
苏勇
,
张顺科
,
李雨莎
,
刘群
,
付广艳
,
朱勇
稀土
通过光学显微镜、X射线衍射、扫描电镜和热重分析等研究了添加钇对Fe-Si合金在900 ℃和1000℃、0.1 MPa纯氧气中高温氧化行为的影响.结果表明,随着元素钇含量的增加,Fe-3Si-0.5Y和Fe-3Si-5.0Y合金的晶粒尺寸较Fe-3Si-0Y合金降低约80％和94％,同时,根据X射线分析结果,合金表面氧化膜的晶粒尺寸随着合金晶粒尺寸的降低明显减小.晶粒细化使合金及其氧化膜中的晶界数量增加,并进一步地促进了合金元素和氧在其中的扩散以及SiO2和Y2O3的形成.然而,含钇合金在900℃和1000℃氧化时均未生成单一连续的SiO2或Y2O3氧化层,但晶粒细化后硅和钇氧化物的快速形成及部分地横向连接对元素的扩散仍起到了比较有效的抑制作用,含钇合金的氧化抗力因此得到了提高.讨论了添加元素钇导致的合金晶粒细化对Fe-Si合金氧化行为的影响机制.
关键词:
氧化
,
晶粒细化
,
钇
,
Fe-Si合金
