一种原位TiB_2颗粒增强铝基复合材料的制备及特性

以Al-6Cu-0.2Mg-1Mn合金为基体,采用混合盐原位反应法制备不同TiB2颗粒含量（质量分数分别为1%、3%、5%）的颗粒增强铝基复合材料,对不同处理状态的TiB2颗粒增强复合材料及Al-6Cu-0.2Mg-1Mn合金的相结构与显微组织进行分析,并测试其维氏硬度。结果表明,原位反应生成的TiB2颗粒能改善基体组织,阻止基体晶粒生长的方向性,得到等轴晶;随着增强相TiB2颗粒含量的增加,基体组织得到明显细化;不同处理状态3%及5%含量TiB2颗粒增强复合材料的维氏硬度均显著高于相应Al-6Cu-0.2Mg-1Mn合金的维氏硬度。     

NaF-K2TiF6-TiO2体系中直接电解制备钛的可行性研究

以NaF-K2 TiF6作为熔盐电解质,TiO2作为溶质,探究直接电解TiO2制备金属钛的可行性.通过对比不同摩尔比NaF-K2 TiF6的初晶温度和TiO2溶解度以选择较为合适的熔盐体系,而后对该体系进行热力学计算、三电极体系循环伏安测试(Mo棒作为工作电极和参比电极,高纯石墨作为对电极)和180min的双电极恒流电解(不锈钢棒作为阴极,石墨作为阳极).结果表明,摩尔比为1.5:1的NaF-K2 TiF6体系可作为电解钛的电解质,TiO2的溶解以化学形式溶解为主,其溶入形式以K2 NaTiOF5为主,以Na2 Ti3 O7为辅.且少量TiO2溶解后会降低熔盐体系的初晶温度.T4+的阴极过程分为两个阶段:TiF62-/TiF63-;Ti3+/Ti.热力学上钛的氧化物优先反应,二氧化钛的还原是逐级进行的.恒流电解阴极产物的钛以小颗粒形式存在并夹杂着一定程度的电解质.     

基于SHS制备Al-Ti-C晶粒细化剂的正交试验研究

利用Al液的高温．使加入其中的Al、Ti、C混和粉末发生SHS反应，制备出了Al-Ti-C中间合金晶粒细化剂。采用正交试验法，研究了Al液的温度、混和料中Al、Ti粉的含量及C／Ti比值对制备的Al-Ti-C晶粒细化剂组织结构的影响．并确定了该细化剂的最佳制备工艺条件，考察了制备的Al-Ti-C晶粒细化剂对工业纯Al的晶粒细化效果。结果表明：当Al液的温度为900℃，Al粉和Ti粉的加入量(质量分数)分别为20％和5％，且混合料中ω(C)：ω（Ti)=1：15时，制备的Al-Ti-C中间合金由块状Al3Ti、粒状TiC和Al基体组成，对工业纯Al具有良好的晶粒细化效果。     

熔体热历史对Al-80%Si合金凝固特性的影响

为了研究熔体热历史对Al-80%Si合金凝固特性的影响,采用高速摄影仪和扫描电镜分别对Al-80%Si合金熔体在不同过热温度与保温时间下初生硅结晶过程进行了动态观测,获得了初生硅结晶形貌与过热温度和保温时间的关系.研究结果表明:随过热温度的升高和保温时间的延长,Al-80%Si合金凝固时过冷度增大,初生硅小平面生长方式减弱.在2min保温时间下过热温度超过100K或在50K过热温度下保温时间超过5min时,初生硅形态由粗大的长条多面体变为均匀细小的等轴多面体.说明熔体热历史可以有效地细化Al-80%Si合金中的初生硅.     

Mechanism and kinetic model of <Emphasis Type="Italic">in-situ</Emphasis> TiB<Subscript>2</Subscript>/7055Al nanocomposites synthesized under high intensity ultrasonic field

In-situ TiB2/7055Al nanocomposites are fabricated by in situ melt chemical reaction from 7055Al-K2TiF6-KBF4 system under high intensity ultrasonic field,and the mechanism and kinetic model of in-situ melt chemical reaction are investigated.X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicate that the sizes of in-situ TiB2 nanoparticles are in the range of 80-120 nm.The results of ice-water quenched samples show that the whole process contains four stages,and the overall in-situ reaction time is 10 minutes.The in situ synthesis process is controlled mainly by chemical reaction in earlier stage (former 3 minutes),and by the particulate diffusing in later stage.The mechanism of key reaction between Al3Ti and AlB2 under high intensity ultrasonic in the 7055Al-K2TiF6-KBF4 system is the reaction-diffusion-crack-rediffusion.Furthermore,the reactive kinetic models in 7055Al-K2TiF6-KBF4 system are established.     

Processing technique and sliding friction and wear behavior of TiB2／ZA27 composite

In-situ TiB2 particles reinforced ZA27 composite was prepared by the stir-casting technique and a twostep method. TiB2/Al composite was produced by incorporating K2 TiF6, KBF4 salts and other agents into Al melt. As a master alloy, TiB2/Al composite was used to manufacture TiB2/ZA27 composite, which results in the generation of well-distributed reinforcing TiB2 phase. The hardness, friction and wear behavior of TiB2/ZA27 composite were investigated. The results show that the hardness of the composite is enhanced with increasing the content of TiB2 particles, the incorporation of TiB2 reduces the wear rate of TiB2/ZA27 composite and improves the friction property under lubricated and dry sliding friction conditions. The worn track width of ZA27 alloy is 1.6 and 2.5 times as long as that of 2.1%TiB2/ZA27 composite at 150 N and 700 N load under lubricated conditions, which indicates that TiB2/ZA27 composite possesses higher bearing ability.     

喷射沉积高硅铝合金的显微组织研究

通过金相显微镜、扫描电镜和X射线衍射分析等手段,对Al-22Si-4.5Fe-1.5Mg-4.5Cu合金的喷射沉积态、挤压态以及热处理态的微观组织进行了观察及分析.结果表明：沉积态中初生硅相细化,合金经热挤压后组织致密、晶粒细小,热处理后合金第二相颗粒数量增加,尺寸未见明显改变,合金主要由α-Al,β-Si,β（Al5FeSi）,Al8Si6Mg3Fe,FeSi2,Al8Fe2Si等物相组成,热处理后新析出了细小的Al2Cu和Al2CuMg相,且以Al2Cu相为主.     

超细晶Al-5Ti-xC的制备及对铝合金的细化机制

通过对Al-5Ti-xC进行快速凝固超细晶化处理以期更好的发挥其对铝合金组织孕育细化能力.将自制的Al-5Ti-xC细化剂在105~106℃/s的冷却速度下快速凝固,制备出宽约2 mm、厚约0.1 mm左右的薄带状产物.结果表明,经过快速凝固处理后的超细晶Al-5Ti-xC细化剂铸态组织中存在Al3Ti及TiC相,其中Al3Ti相得到很明显的细化,并且TiC更加弥散.向工业纯铝中加入2%的块状细化剂可以达到很好的细化效果,而加入0.5%的薄带状细化剂即可达到相同的细化效果.向ZL109中加入薄带状细化剂力学性能比加入块状细化剂有了较大的提高,硬度增加10%,高温拉伸强度增加11.4%.     

Ni-20Cr-2．5Al在Cl^-溶液中腐蚀行为研究

利用电化学方法及化学浸泡法，结合OM、XRD、TEM等表面分析技术，研究机械合金化Ni-20Cr-2．5Al及粗晶Ni-20Cr-2．5Al合金的电化学腐蚀性能．实验结果表明：机械合金化方法制备的Ni-20Cr-2．5Al合金在Cl^-溶液中腐蚀性能不如粗晶Ni-20Cr-2．5Al合金．相对于粗晶合金，晶粒细化是合金机械合金化后耐蚀性能降低的主要原因．     

稀土Y对Mg-6Al—0．2Mn组织和力学性能的影响

针对AM60合金(Mg-6Al-0.2Mn)室温强度和耐热性较低的问题,采用光学显微镜、扫描电镜(SEM)、透射电镜(TEM)以及电子万能拉伸试验机,研究了不同质量分数(0%～1.2%)的Y对AM60合金显微组织和力学性能的影响.结果表明:加入0.4%Y时,AM60合金的晶粒组织得到显著细化,第二相为不连续的骨骼状,其相组成为α-Mg+Al2Y+Mg17Al12,并随着Y含量的增加,合金的第二相由不连续骨骼状变为连续网状分布.随后的T6处理使合金组织中的粗大第二相消失,出现细小的时效析出相Mg17Al12.加入0.4%Y时并进行T6处理可以提高合金的室温和高温抗拉强度,与AM60合金相比,其室温抗拉强度提高了40%,523K时的抗拉强度提高了35%.     

Microstructure Characteristics and Apparent Viscosity of Hypereutectic Al-24%Si Alloy Melt During Semi-solid State Stirring

The microstructural evolution and apparent viscosity of hypereutectic Al-24%Si alloy during semi-solid state shearing were studied with a Searte type viscometer. When the alloy melt was continuously stirred from 720℃ to eutectic temperature, the primary Si crystals were gradually changed from elongated platelets to near-spherical shapes. It was found that some nondendritic a-phase formed when the melt was stirred below 585℃. The experiment showed that the semi-solid stirring had strong effect on inhibiting the anisotropic growth of Si crystals during solidification. The apparent viscosity of the alloy melt increased slowly with the decreasing of temperature before the formation of nondendritic α-phase, which caused the dramatic increase of apparent viscosity.     

制造工艺对Al—Ti—B中间合金细化性能的影响

研究了制造工艺对ＡｌＴｉＢ中间合金细化性能的影响。结果表明，高温反应合成的ＡｌＴｉＢ中间合金中ＴｉＡｌ３相为粗大的条状；低温反应合成的该合金中ＴｉＡｌ３相为较小的块状。在短保持时间细化时，高温反应合成的该合金具有十分优异的细化性能；而在长保持时间细化时，高温反应合成的该合金表现出强烈的细化能力。冷却速度影响合金中ＴｉＢ２相的分布。ＴｉＡｌ３相是影响该合金细化性能的主要因素。     

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.     

半固态A1-10%Cu合金流变行为

利用同轴双筒流变仪研究了半固态Al-10％Cu合金的流变行为,发现在连续冷却试验中,被剪切半固态合金浆液的表观粘度随着固相分数以及冷却速度的上升而增加,随切变速率的上升而下降;在等温试验中,其表观粘度随等温时间的上升而下降,大约1000s后达到“稳态”值。     

Melt Treatment of Al-7%Si Alloy by Flux Injection

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Effects of Extrusion Processing on Microstructure of 7075Al Alloy in the Semi-solid State

A recrystallization and partial melting(RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion experiments were conducted to comparatively investigate the optimum extrusion process parameters. Commercial 7075 Al alloy samples were firstly extruded with varying extrusion ratios below the recrystallization temperature followed by homogenization, then these samples were reheated to the semi-solid state and held in the range of 5 to 50 minutes. The experimental results show that varying process cause the difference in the deformation degree and microstructure for as-extruded samples, resulting in various semi-solid microstructure. It is verified that the formation of equiaxed grains in semi-solid microstructure depends on recrystallization behavior of extruded samples during partial melting. Both relative high extrusion temperature and low extrusion ratio lead to high volume fraction of recrystallized area, thus entirely equiaxed solid grains in semi-solid 7075 Al alloy samples can be obtained finally. In addition, Ostwald ripening was determined as the dominate coarsening mechanism of solid grains in semi-solid state for this 7075 Al alloy during the RAP route. The influence of predeformation on recrystallization behavior of this 7075 Al alloy was discussed in detail.     

Grain Refining Performance of SHS Al—50TiC Master Alloys for Commercially pure Aluminum

An Al-50wt^TiC composite was directly synthesized by self-propagating high-temperature synthesis(SHS) technology,and then was used as a grain refining master alloy for commercially pure aluminun.The microstructure and grain refining performance of the synthesized master alloy were emphatically investigated.The SHS master alloy only ocntained submicron TiC particles except for Al matrix.Moreover,TiC particles were relatively free of agglomeration.Grain refining tests show that adding only 0.1wt^ of the master alloys to the aluminum melt could transform the sturcture of the solidified samples from coarse columnar grains to fine almost 1.5h at 1003K.Therefore,it is concluded that the SHS master alloy is an effective grain refiner for aluminum and its alloys,and that it is highly resistant to the grain refining fading encountered with most grain refiners.     

Thermodynamic Stability of the Molding Materials for Casting Ti-6Al-4V Alloy

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挤压及半固态等温处理对Al-30%Si合金组织的影响

对Al-30%Si合金进行挤压变形并进行半固态等温处理,以求获得细小、圆整的初生硅颗粒.利用光学显微镜、Image Pro Plus金相分析软件等手段测定处理后的初生硅平均直径和形状因子.结果表明,挤压变形能显著细化初生硅颗粒.而半固态等温处理时,加热温度和保温时间均会对合金组织产生显著影响.在640℃保温10min可获得较佳的合金组织.