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 共查询到19条相似文献,搜索用时 171 毫秒
1.
Ti—6Al—4V合金ISM熔炼过程中Al元素的挥发损失行为   总被引:1,自引:1,他引:0  
郭景杰  刘源 《铸造》1999,(2):14-18
以二元合金的Miedema生成热模型和以Kohler建立的三元溶液混合焓模型为基础,计算了Ti6Al4V合金中各组元的活度系数,在此基础上系统研究了该合金的ISM熔炼过程中Al元素的挥发损失行为。研究结果表明:在真空室压力为0133Pa(10-3mmHg)的条件下,当熔体温度低于2100K时,Al元素的挥发受界面挥发反应控制;而当熔体温度高于2100K时,则受界面挥发反应和液相边界层中的扩散双重控制。最后计算了不同外压和熔体温度条件下Al元素的挥发损失量,为实际熔炼过程提供了理论指导。  相似文献   

2.
研究了Ti-47Al合金添加少量Nb、Cr、V元素(1at%-2at%)并经恒温锻造后,在不同热处理制度下的显微组织特征,以及Nb、Cr、V对合金组织的影响。结果表明,Ti-47Al-2Nb-1Cr-1V及Ti-47Al-2V-1Cr合金的热处理组织形貌主要取决于高温处理的温度、在(γ+α)两相区,稍低于Ta温度处理时,α相显著粗化,随加热温度的降低,α、γ两相均明显细化,进一步降低加热温度,发生γ,相的明显粗化。通过控制高温加热温度及时间,可以有效地控制合金的组织,使其获得全片层、近片层、双态、近双态、近γ以及细化的近γ组织。  相似文献   

3.
郭景杰  刘源 《金属学报》1999,35(4):416-420
计算了Ti-24Al-11Nb中各组元的活度系数,在此基础上系统地研究了该合金在冷坩蜗感应凝壳熔炼过程中Al的发挥发损失行为。计算结果表明外压为0.133Pa时,在1900-2200K的范围内,Al的挥发由界由挥发反应和液相界面层中的扩散同时控制作用。  相似文献   

4.
EFFECT OF Cr ON MICROSTRUCTURE OF Ti_3Al+TiAl ALLOYS   总被引:3,自引:0,他引:3  
郑运荣  赵林岩 《金属学报》1994,30(3):97-103
研究了Ti-44.9Al(at.-%)和Ti-44.3Al-3Cr(at.-%)合金的铸态组织及其在热处理过程中的变化。结果表明:Cr增加了Ti-Al合金中TiAl(γ)相的含量,促使Ti3Al(α2)相由片状变成块状;加速了α2+γ片状组织的不连续粗化过程,形成了尺寸较小的新生α2+γ晶。因此,加Cr和1150℃长时热处理是细化α2+γ两相合金铸态粗晶组织的有效途径;Cr促进有序体心立方β2相的  相似文献   

5.
在Al-Ti-Nb-8Mn四元系邻近L12型Al3Ti-8Mn成份区合金中,随Nb含量变化,其显微组织发生明显变化。通过对不同合金的微观组织的考察,进一步确认了在Al67Mn8Ti25基金中加Nb并相应调整Al和Ti含量可形成DO22型Al3(Ti,Nb),L10型TiAl和Ga2Hf型Al2Ti3种类型的第二相。本文列举了Al67Mn8tI23Nb2,Al65Mn8Ti26-5Nb0.5,Al5  相似文献   

6.
研究了Ti3AL,Ti3Al-Nb及TiAl金属间化合物在900℃及950℃空气中当表面有(0.9Na,0.1K)2SO4盐膜存在时的高温热腐蚀行为.结果表明,Ti3Al,TiAl金属间化合物在900、950℃遭受严重的热腐蚀.合金表面均没有形成单一的A12O3保护层,而是形成外层为富TiO2层,内层为TiO2、A12O3或Nb2O5的混合氧化物层,在氧化膜/合金基体界面形成一些硫化物.合金的腐蚀以电化学机制进行.硫化物的形成也促进了电化学反应的阳极过程.向Ti3Al中添加Nb可以显著地改善其热腐蚀性能,这归因于Nb促进富Al氧化物内层的形成.TiAl的耐蚀性能优于Ti3Al基合金.  相似文献   

7.
卢斌  李东 《金属学报》1995,31(9):B413-B417
对Ti3Al-Mo-Nb,Ti3Al-Nb-V,TI3Al-Zr-V三个赝三元合金系的实验结果表明,α2/α2+β相界遵守电子浓度规律,且合金元素的电子数由它们的电子结构决定,过渡族Ti,Ti,Zr,V,Mo,Nb的价电子为s+d电子,即NTi=NZr=4(s^2d^2),Nv=5(s^2d^3),NNb=5(s^1d^4)NMo=6(s^1d^5);非过渡族元素Al的价电子为s+p电子,即NAl  相似文献   

8.
浇注时功率(ISM)对TiAl基合金铸件表面质量的影响   总被引:11,自引:6,他引:5  
采用感应凝壳熔炼(ISM)法熔炼了Ti-48%Al-2%Cr-2%Nb合金,以静态浇注和离心浇注两种条件在金属型中浇注了汽车排气阀。通过分析阀体的成形情况,总结了浇注时功率对合金填充能力和铸件表面质量的影响规律。结果表明,ISM法熔铸TiAl基合金时,合金的线收缩量随浇注时功率的提高而增大,离心浇注可有效地抑制收缩,浇注时功率处于200至280kW范围内所得铸件表面质量较为理想。  相似文献   

9.
研究了Mn对Ti-45Al-10Nb(原子分数)合金铸态组织和1100℃再结晶组织的影响以及Mn对于Ti-45Al-10Nb合金力学性能的影响。结果表明,Mn能促进Ti-45Al-10Nb合金的再结晶过程,并改善合金的力学性能  相似文献   

10.
锰对Ti—45Al—10Nb合金的组织和性能的影响   总被引:1,自引:1,他引:0  
研究了Mn对Ti-45Al-10Nb(原子分数)合金铸态组织和1100℃再结晶组织的影响以及Mn对于Ti-45Al-10Nb合金力学性能的影响。结果表明,Mn能促进Ti-45Al-10Nb合金的再结晶过程,并改善合金的力学性能。  相似文献   

11.
TiAl-based Intermetallic alloys are being considered as structural materials for high-temperature applications due to their low density and substantial mechanical strength at high temperatures. The effect of various elements added by ion implantation on the oxidation behaviour of near-γ Ti-48Al-2Cr and Ti-48Al-2Cr-2Nb (compositions are given in at-%) in air at 800°C has been studied. Ions implanted (1017 Ions/Cm2) were Al, Ti, Cr, Mo, Y, Mn, Pt, Nb, and Si in case of Ti-48Al-2Cr and Nb in case of Ti-48Al-2Cr-2Nb. Comparison was made with the oxidation behaviour of Ti-48Al2Cr-2Nb and Ti-47Al-2Cr-0.2Si alloys in which quaternary elements were added by alloying. It is Concluded that ion implantation can serve as a research tool to study, in the frame of screening tests, the influence of various elements on the corrosion behaviour of materials.  相似文献   

12.
Based on activity calculation model, t he activity coefficients of Ti, Al and Nb components of Ti-25Al-25Nb (mole fraction, %) melt, the vapor pressu res of correspo nding components and the evaporation loss rates were calculated. Utilizing these activity coefficients and the vapor pressures, the relative evaporation coeffic ient is used to judge the evaporation tendency of these components. The evapora tion tendency among the three components were compared and the result shows that the evaporation tendency is that: AlTi>Nb. Evaporation loss rate increases with the increase of melting temperature and decreases with the increase of chamber pressure. There exists an impeding pressure pimpe of Al element evapo ration during induction skull melting process of Ti-25Al-25Nb alloy. The impeding pressu re can be written as pimpe=8.1pe, where perepresents the equilibrium partial pressure. The calculation of evaporation loss of Al element also showed that when chamber pressure exceeds pimpe, the Al volatilization losses could be ignored. In order to prevent the evaporation loss of components, the pressure in the vacuum chamber should not below pimpe.  相似文献   

13.
低压预处理对TiAl抗氧化性的影响   总被引:3,自引:0,他引:3  
对5种TiAl基合金进行了10^-3Pa/1040℃/9h/FC(炉冷)表面预处理。随后进行的900℃静止空气中100h断续氧化实验表明,TiAl的抗氧化性不但没有提高,反而明显下降。抗氧化性下降的主要原因在于低压预处理过程中合金元素(尤其是铝元素)的选择性蒸发导致TiAl表面活化并形成Ti3Al相,而Ti3Al的抗氧化性较差,从而使TiAl整体氧化增重增加。  相似文献   

14.
Saturated vapour pressures of the Al, Ti and Nb components in Ti—13Al—29Nb—2·5Mo (wt-%) melts were calculated at arbitrary temperatures. The calculated values at 2150 K for Ti, Al and Nb were 2·0, 30·7 and 0·17 Pa, respectively. From the thermodynamic point of view, the principal evaporation loss is of the Al component. Based on the saturated vapour pressure, the mass transport coefficient of the Al component, evaporation loss rates of the Ti, Al and Nb components and the evaporation loss of the Al component were calculated. When the melt temperature is 2100 K, the evaporation control changes from the double control mode to the single interface volatilisation control mode with increasing chamber pressure at a transition pressure of about 4 Pa. The rates of evaporation loss of the components are NAl≈15NTi≈46NNb. A critical chamber pressure of about 13·33 Pa exists during induction skull melting of the Ti—13Al—29Nb—2·5Mo alloy. In order to prevent the evaporation loss of Al, the chamber pressure should be kept above 13·33 Pa. The theoretical calculation of the evaporation loss of the Al component is in good agreement with experimental values. IJCMR/432  相似文献   

15.
The mathematics model for temperature field of water-cooling copper crucible induction skull melting process was established. The program for simulating temperature field of melting process was developed with finite element method. The temperature field of the melting process for Ti-47Al-2Cr-2Nb aUoy was calculated. During melting period, the temperature is raised gradually along radius augmentation direction. The elements of the charge near the crucible wall are molten first. The center elements of the charge are molten last. The melting time of the center element is just that of all the charge melting. The melting time of Ti-47Al-2Cr-2Nb alloy is 15min. In which, the charge was heated by low power 80kW for 9min and by high power 300kW for 6min. When melting Ti-47AI-2Cr-2Nb aUoy,the loading power is nearly direct proportion to melt temperature. Increasing loading power may raise melt temperature. The best melting power of Ti-47Al-2Cr-2Nb alloy is 305-310kW. This is identical with the melting test and has guidance sense to the melting process of actual titanium aUoy.  相似文献   

16.
在基于活度系数计算模型的基础上,计算了ISM熔炼过程中不同熔炼温度下Ti-13Al-29Nb-2.5Mo(ω/%)熔体中Ti,Al,Nb元素的饱和蒸气压,计算结果表明,在熔炼温度范围内,Al元素的饱和蒸气压分别比Ti,Nb元素的饱和蒸气压大17倍和3070倍左右。在熔炼温度范围内对熔体中Al,Ti,Nb元素的挥发损失速率的计算表明,Al元素在损失速率比Ti,Nb的损失速率分别大43倍和144倍左右,在此基础上计算了Ti,Al,Nb元素的挥发损失量以及合金在熔炼后的化学成分,结果表明由于合金中各组元的挥发损失速率大小不一,使得熔炼前后合金的成分出现了变化。分析表明合理降低熔炼温度及增加真空室中压力可以减小成分的变化。本结果为ISM熔炼实践中合金成分控制提供有价值的理论指导。  相似文献   

17.
研究了Ti2Al Nb基合金Ti-22Al-(27-x)Nb-x Zr(x=0,1,6,at%)在650~800℃的氧化行为。采用XRD和SEM等测试技术对此温度区间形成的氧化层特征进行了分析。结果表明,相比Ti-22Al-27Nb,含锆合金具有较好的抗氧化性能。Ti-22Al-(27-x)Nb-x Zr合金在650℃氧化100 h,主要氧化产物为Ti O2,而在800℃氧化100 h,Ti O2,Al2O3和Al Nb O4为主要产物,但是在Ti-22Al-21Nb-6Zr合金中还有Zr O2生成。Ti-22Al-26Nb-1Zr合金具有优异抗氧化性能,归因于氧化产物细化形成了致密的氧化层,而Ti-22Al-21Nb-6Zr合金,虽然在800℃也形成了较多Al2O3,但是氧化层中的Zr O2为氧的快速扩散提供通道,进而导致该合金氧化增重明显。  相似文献   

18.
B元素对Ti-46Al和Ti-46Al-5Nb合金柱状晶组织的影响   总被引:2,自引:0,他引:2  
B元素对Ti-46Al和Ti-46A1-5Nb(原子分数,%)合金的柱状晶组织均有明显的细化作用,且对后者的细化效果更显著.这一现象可归结为:B元素在Ti-46Al-5Nb合金中的溶解度较低,硼化物析出量增加,柱状晶组织进一步细化.  相似文献   

19.
采用机械球磨与热压烧结相结合的粉末冶金法对不同球磨时间Nb-35Ti-6Al-5Cr-8V-5C合金的粉末变形行为,微观组织结构和力学行为进行研究。结果表明:随着球磨时间的增加,Nb-35Ti-6Al-5Cr-8V-5C复合粉末中的块状金属颗粒首先变形为片状后在碰撞挤压作用下破碎成絮状,TiC粉末均匀的分布于片状金属粉末表面;Nb-35Ti-6Al-5Cr-8V-5C合金由Nbss和(Nb,Ti)C两相构成,各合金碳化物体积分数均为11%左右,Ti元素主要分布于Nbss晶界和碳化物内,Al、Cr、V元素主要分布于Nbss晶粒内,Nbss和(Nb,Ti)C相尺寸均随球磨时间增加而尺寸减小;Nbss晶粒细化及强化相碳化物弥散化导致合金的室温压缩力学性能和塑性变形能力显著提高,压缩变形后合金Nbss与碳化物具有良好的界面结合能力,但是碳化物内部存在明显的近似平行分布的裂纹;数据对比表明,粉末冶金法制备Nb-35Ti-6Al-5Cr-8V-5C合金的力学性能优于电弧熔炼法。  相似文献   

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