东秦岭松树沟超镁铁岩体铬铁矿成矿特征分析

以东秦岭松树沟超镁铁岩体的产状和铬铁矿的产出特征为背景，结合铬铁矿的组分特征，对副矿物铬铁矿和不同矿石类型铬铁矿的穆斯堡尔谱进行成矿特征方面的解释；并通过与铬铁矿形成有关的宏观和微观地质现象分析，指出铬铁矿体是地幔岩高度熔融形成的富铬和镁的极端部分。     

东秦岭松树沟铬铁矿矿物组份特征及其成矿条件分析

本文主要叙述了东秦岭松树沟铬铁矿矿物的组分特征和不同产状铬铁矿矿物组分的变化规律，并在此基础上分析了铬铁矿矿物的形成条件，论述了松树沟铬矿床的成矿过程。     

河北平泉下金宝花岗斑岩锆石U-Pb年代学、Hf同位素特征及其地质意义

下金宝岩体位于永安-下营坊-毛家沟构造岩浆岩活动带上,与本区金、银、铜等多金属成矿关系密切。对下金宝含矿花岗斑岩的锆石进行LA-MC-ICP-MS U-Pb年代学和微量元素地球化学研究,岩体锆石U-Pb年代学表明,锆石206Pb/238U加权平均年龄为(158.0±2.5)Ma(1σ,MSWD为0.76,n=16),表明该岩体形成于燕山早期。锆石Ti温度计计算结果显示,下金宝岩体中锆石的结晶温度除一个测点小于700℃外,其余测点温度均大于700℃,表明锆石结晶于形成深度较深、温度较高的岩浆。锆石εHf(t)为-10.913~-7.5828,均为负值,Hf同位素特征表明,下金宝岩体主要起源于下地壳岩石的部分熔融,形成于由挤压向伸展转换的大地构造环境中。其动力学机制如下:燕山早期华北地块发生岩浆底侵作用,下地壳岩石重熔,并伴有部分地幔物质的参与,形成深部岩浆房,在深部压力作用下,原始岩浆沿深断裂上升,岩浆在演化过程中发生结晶分异作用,导致岩浆出溶流体,形成富水的岩浆热液,在近地表伴随温度和压力的降低,岩浆冷凝形成本区含矿斑岩体。     

大别山姚冲花岗岩锆石U-Pb年龄、Hf同位素及地质意义

姚冲斑岩型钼矿床位于东秦岭-大别山钼成矿带,矿体产于花岗岩外接触带大别片麻杂岩中。矿体下部的隐伏岩体岩性主要为二长花岗岩和花岗斑岩。LA-ICP-MS锆石U-Pb定年结果表明:二长花岗岩和花岗斑岩的侵位年龄分别为(139.6±2.0)Ma和(139.8±2.2)Ma,形成于晚侏罗世-早白垩世。锆石Hf同位素分析结果表明:姚冲钼矿区花岗岩的εHf(t)值范围为-30~-22.8,位于地幔演化线之下,tDM2值范围为2.21~2.60 Ga,表明其源于扬子板块北缘的古老地壳,其组成类似于扬子板块北缘TTG型岩浆岩。姚冲钼矿床形成于晚侏罗世-早白垩世构造体制从挤压收缩向区域性伸展的大转换阶段,扬子板块拆沉作用导致软流圈上涌,诱发加厚下地壳部分熔融产生的花岗质岩浆,为姚冲钼矿床成岩成矿作用提供了物质来源。     

激光重熔对TiAl合金表面等离子喷涂热障涂层耐热腐蚀性能的影响

分别采用等离子喷涂和等离子喷涂一激光重熔复合工艺在TiAl合金表面制备了热障涂层,研究了两种涂层在850℃：下75％Na2SO4＋25％NaCl（质量分数）熔融盐中的热腐蚀行为,进而分析激光重熔工艺对等离子喷涂热障涂层耐热腐蚀性能的影响。结果表明：激光重熔热障涂层可以有效地阻止熔融盐腐蚀介质进入涂层发生腐蚀,具有更优的抗热腐蚀性能和使用寿命。     

半固态AZ91D镁合金的触变性

利用Couette型同轴双桶流变仪，对等温搅拌和重熔加热的半固态AZ91D镁合金浆料的触变性能进行了研究．实验结果表明：经过连续降温和等温搅拌，半固态浆料的表观粘度逐渐降低，并达到一个稳态值；此时，若停止搅拌剪切，并经过某一时段的等温静置，再次在某一剪切速率下搅拌时，半固态浆料的表观粘度会突然升高，然后再迅速降低，最后到达一个稳态值，呈现出典型的剪切变稀特性；延长静置时间、或增加固相分数、或降低剪切速率，再次剪切搅拌时，半固态浆料到达稳态表观粘度的时间随之增长，同时稳态表观粘度值也相应增大；重熔加热后的半固态浆料的稳态表观粘度比相同固相分数的等温搅拌的半固态浆料的稳态表观粘度低；随重熔加热保温时间的延长，半固态浆料的稳态表观粘度逐渐降低，当稳态表观粘度达到最低值后，随重熔加热保温时间的延长，稳态表观粘度又逐渐增大．     

宁芜早白垩世火山岩地球化学特征及岩浆演化

宁芜盆地位于中国东部长江中下游成矿带,盆地内主要发育4套火山岩。本研究主要通过地球化学手段探究该火山岩地球化学性质及岩浆演化特征。结果表明:火山岩主要为安山岩、粗安岩和英安岩;早期龙王山组为低钾系列,其余3组火山岩为高钾钙碱性-橄榄玄粗岩系列。4套火山岩Mg~#值为66.51~40.33,轻稀土富集,Ta、Nb、Ti亏损,指示原始岩浆形成于富集地幔部分熔融。原始岩浆形成后经历了以分离结晶为主的岩浆演化过程,主要表现为Mg~#降低和向富碱系列演化。结合区域地质和年代学研究,认为宁芜火山活动发生在受古太平洋俯冲和大别造山后区域引张的共同作用下的岩石圈减薄环境,郯庐断裂早白垩世走滑使得宁芜盆地拉分和富集地幔减压熔融形成岩浆。     

基于相场格子玻尔兹曼模型的铝合金LSPSF非枝晶形成（英文）

采用数值模拟研究基于低过热度剪切制浆机铝合金凝固初期非枝晶组织的形成。采用格子玻尔兹曼法和相场法相结合,模拟枝晶在凝固过程中的生长和运动。模拟结果表明,充分的剪切流有助于浓度场的均匀化、晶体的旋转和非枝晶的形成。讨论晶粒间的相互作用。在枝晶臂部分重熔的基础上,建立LSPSF枝晶断裂判据,发现强剪切流和较大的倾斜角度能够增强枝晶断裂,并对模拟结果进行实验验证。     

激光重熔对金属陶瓷Mo-ZrO_2组织和耐蚀性能的影响

针对金属陶瓷Mo-ZrO2抗液态铁腐蚀问题,采用CO2激光器对金属陶瓷Mo-ZrO2进行表面重熔。采用X射线衍射仪和扫描电子显微镜分析重熔后金属陶瓷表面的相组成和形貌,用光学显微镜和SEM分析测试了重熔层厚度和孔隙率。结果表明:在激光快速加热和冷却作用下,Mo-ZrO2表面大部分金属钼以MoO3的形式挥发,氧化锆经熔化、凝固,在表面形成以柱状晶为主的氧化锆重熔层;重熔层的厚度随着激光能量密度增大而增大,最大可达430.2μm;随着激光能量密度增加,重熔层孔隙率出现先增加后降低的变化,最低达到4.29%;重熔层与基体的结合强度,随着激光能量密度的增加而递减;当激光能量密度为4J/mm2,最大结合强度为17.33 MPa。在1 650℃高温条件下,进行6h熔融金属腐蚀试验,激光重熔使金属陶瓷降低了Mo和Zr元素向熔池扩散速率,显著提高金属陶瓷Mo-ZrO2抗液态铁腐蚀性能。     

不同部分重熔温度对半固态过共晶高铬白口铸铁初生相形貌的影响

为了考察部分重熔温度对初生碳化物形貌的影响,对过共晶高铬铸铁半固态坯料分别在3个不同温度(1 230℃、1 250℃、1 270℃)进行部分重熔,重熔时间为15 min,并借助Leica图像分析仪分别定量描述了初生碳化物形状因子及粒度因子的变化规律.研究表明,半固态组织中初生碳化物形状随着部分重熔温度的升高,呈先改善然后恶化,最后明显改善的趋势变化;碳化物尺寸随着部分重熔温度的升高而逐渐减小.初生碳化物演化过程是由溶质扩散和固、液相界面张力共同作用的结果,然而在较低的部分重熔温度下,固、液相界面张力的作用不明显.在1 270℃部分重熔温度下,重熔15 min时,可获得理想的部分重熔组织.     

Microstructure and Element Distribution during Partial Remelting of an Al-4Cu-Mg alloy

The effects of the isothermal temperature and holding time on the microstructure and element distribution have been investigated during partial remelting of the semisolid Al-4Cu-Mg alloy. The experimental results show that the optimal process parameter should be chosen at isothermal temperature of 540-580 °C with the holding time of less than 10 min. Coalescence and coarsening of α grains occur at low liquid fraction. At high liquid fraction, coarsening of α grains and melting of small grains were promoted by an increase of the isothermal temperature and the holding time. The coalescence of grains and Ostwald ripening are two main mechanisms of the microstructural evolution during partial remelting. Meanwhile, the higher the isothermal temperature and the longer the holding time, the more segregation of Cu at the grain boundary would be, which conform to the theory of element distribution affected by heating condition.     

Application of cyclic upsetting-extrusion to semi-solid processing of AZ91D magnesium alloy

The microstructural evolution of AZ91D magnesium alloy prepared by means of the cyclic upsetting-extrusion and partial remelting was investigated. The effects of remelting temperature and holding time on microstructure of semi-solid AZ91D magnesium alloy were studied. Furthermore, tensile properties of thixoextruded AZ91D magnesium alloy components were determined. The results show that the cyclic upsetting-extrusion followed by partial remelting is effective in producing semi-solid AZ91D magnesium alloy for thixoforming. During the partial remelting, with the increase of remelting temperature and holding time, the solid grain size increases and the degree of spheroidization tends to be improved. The tensile mechanical properties of thixoextruded AZ91D magnesium alloy components produced by cyclic upsetting-extrusion and partial remelting are better than those of the same alloy produced by casting.     

挤压铸造制备半固态AZ61镁合金的组织演变及力学性能(英文)

采用挤压铸造后直接二次重熔的方法制备半固态AZ61镁合金。首先通过挤压铸造预成形铸态AZ61镁合金,以获得细小的枝晶;然后在半固态区间进行二次重熔,细小的枝晶演变成球状晶,完全球化的晶粒被液相均匀包裹。研究结果表明:通过挤压铸造预成形的铸态AZ61镁合金与传统铸造预成形的铸态AZ61镁合金相比,在相同的二次重熔条件下,挤压铸造预成形的铸态AZ61镁合金获得更细小的半固态组织。此外,挤压铸造加上二次重熔触变成形的AZ61镁合金,力学性能优于传统铸造后二次重熔触变成形的AZ61镁合金。     

半固态2024合金部分重熔新工艺与组织演变

提出半固态坯料先在液相线以上某温度适当等温加热,然后再降低温度至两相区继续等温保温的两步法部分重熔新工艺.采用该工艺对低过热度浇注半固态2024合金坯料进行部分重熔试验,利用光学显微镜和金相图像分析系统,研究了坯料组织演变规律,并与两相区等温部分重熔工艺进行了比较.结果表明,采用两步法部分重熔工艺.由于坯料升温速度加快和熔化过热温度提高,抑制了晶间共晶相的溶解扩散,晶间液相形成速度明显加快,对晶粒合并长大具有一定的抑制作用,并加速晶粒球化,坯料部分重熔后,晶粒更加细小和圆整.     

Phase field lattice Boltzmann model for non-dendritic structure formation in aluminum alloy from LSPSF machine

The formation of non-dendritic structures in the primary phase of an aluminum alloy solidified using low superheat pouring with a shearing field (LSPSF) machine was investigated by numerical simulation. The growth and motion of a dendrite during solidification was simulated by a combination of the lattice Boltzmann method and the phase field method. The simulation results indicated that enough shear flow helped homogenize the concentration fields, rotate crystals and altere microstructures from dendritic to non-dendritic. The interaction of grains was also discussed. A fragmentation criterion was established based on partial remelting of dendrite arms; fragmentation was enhanced by a strong shear flow and larger inclined angles. The simulation results were verified experimentally.     

用模铸八角锭作为自耗电极生产H13钢电渣重熔锭

通过调整电渣重熔时的冶炼工艺参数,直接以截面差异较大的5.0 t模铸八角锭作为电渣重熔用自耗电极,生产出了质量优良的H13钢电渣重熔锭。该工艺可降低生产成本、缩短生产周期。     

Reducing defects in remelting processes for high-performance alloys

Defect reduction is one of the most important goals in continuing research to improve remelting technologies, such as vacuum arc remelting, electroslag remelting, or hearth melting (plasma or electron beam), of specialty alloys. Ingot defects may originate from several sources in these processes, such as foreign materials in the melt stock or electrode, drop-in material from the furnace interior, and solidification defects. Laboratory-and industrial-scale melting experiments are used by Sandia National Laboratories and the Specialty Metals Processing Consortium to determine relationships between melt-processing conditions and defect formation. Examples described here include freckle formation, a solidification defect in large ingots of alloy 625 (electroslag remelting), and alloy 718 (vacuum arc remelting). These examples demonstrate how integrated melting experiments, process modeling, and ingot analysis can guide the control of melting conditions to reduce defects. Editor’s Note: A hypertext-enhanced version of this article, including video of the arc gap during the vacuum remelting of alloy 718, can be found on the TMS web site at www.tms.org/pubs/journals/JOM/9803/VanDenAvyle-9803.html. James A. Van Den Avyle earned his Ph.D. in metallurgical engineering at the Massachusetts Institute of Technology in 1975. He is currently a principal member of the technical staff at Sandia National Laboratories. John A. Brooks earned his Ph.D. in metallurgy at Carnegie Mellon University in 1981. He is currently a principal member of the technical staff at Sandia National Laboratories. Dr. Brooks is also a member of TMS. Adam C. Powell earned his Ph.D. in materials science and engineering from the Massachusetts Institute of Technology in 1997. He is currently a post-doctoral researcher in metallurgy at the National Institute of Standards and Technology. Dr. Powell is also a member of TMS.     

不锈钢激光熔凝工艺研究

采用激光熔凝技术对1Cr18Ni9Ti不锈钢表面进行单道扫描,研究不同激光工艺参数下熔凝层微观组织和显微硬度的变化.结果表明:激光熔凝区品粒细小,熔凝层显微硬度较基体硬度有所提高,最高硬度可达288HV.可以推断采用激光熔凝技术,能够提高不锈钢的硬度,改善其耐磨性能.     

TiAl合金真空自耗熔炼过程的数值模拟

通过数值模拟研究了直径为180mm的TiAl合金铸锭的真空自耗冶炼过程,获得了TiAl合金真空自耗熔炼过程中熔炼温度、熔炼速度和冷却能力对金属熔池温度梯度、熔池形状和糊状区宽度的影响规律。结果表明,随熔炼温度升高,熔池深度增加,其形状由碗状向V形转变,熔炼温度对熔池中温度梯度和凝固前沿糊状区宽度影响较小;随熔炼速度增加,熔池中温度梯度显著减小,糊状区宽度和熔池深度则明显降低;随冷却能力增加,糊状区宽度明显减小,熔池中温度梯度和熔池深度略有减小。     

Microstructural evolution of fine-grained ZA27 alloy during partial remelting

The microstructural evolution process of fined-grained ZA27 alloy during partial remelting has been investigated.The relationship between the as-cast and semi-solid microstructures has been discussed in particular.The results indicate that a semi-solid microstructure with small and spheroidal primary particles can be obtained when the Z.A27 alloy is partially remelted.The microstructural evolution can be divided into four stages,the initial coarsening of the dendrites due to coalescence of dendrite arms,structural separation resulted from the melting of residual interdendritic eutectic,spheroidization due to the partial melting of solid particles and final coarsening attributed to the coalescence and Ostwald ripening.An equiaxed dendrite in the as-cast microstructure may evolve into one spheroidal particle in the semi-solid microsturucture after being partially remelted.The more equiaxed the dendrites in an as-cast microstructure are,the more spheroidal the solid particles in the semi-solid microstructure will be.Finer primary particles could be obtained if the alloy with finer as-cast microstructure was partially remelted.However,due to the coalescence effect,their sizes cannot be reduced further if the refined as-cast microstructure reached a certain extent.