TiAl预合金粉末热等静压致密化机理及热处理对微观组织的影响

采用感应熔炼气体雾化法(EIGA)制备了Ti-47Al-2Cr-2Nb-0.2W-0.15B(原子分数,%,下同)和Ti-45Al-8Nb-0.2Si-0.3B 2种Ti Al预合金粉末,应用SEM,OM和DSC对预合金粉末进行表征.对Ti Al预合金粉末进行热等静压致密化处理,随后对致密化所得Ti Al合金进行热处理,研究了不同时效温度和冷却速率对Ti Al合金微观组织的影响.结果表明,预合金粉末的冷却速率在105~106K/s之间,随着冷却速率的增加,预合金粉末雾化过程中出现b→a'的马氏体转变.DSC曲线表明,升温过程中在700~800℃之间发生亚稳a2相→g相的转变.在热等静压过程中,预合金粉末初始阶段随机堆积,通过粉末颗粒流动、转动和重排实现致密度的提高.随着温度升高a2相转变为g相;温度进一步升高,粉末颗粒发生显著塑性变形,颗粒间形成烧结颈.随着保温时间的延长,粉末间孔隙主要通过表面扩散、体积扩散和扩散蠕变连接方式完成闭合.Ti-47Al-2Cr-2Nb-0.2W-0.15B预合金粉末热等静压致密化后,其微观组织主要为细小等轴的g相组织,以及少量的a2相和b相.Ti-45Al-8Nb-0.2Si-0.3B预合金粉末热等静压致密化后,其微观组织主要为细小等轴的g相组织,以及少量的a2相和弥散分布的硅化物x-Nb5Si3.时效温度不同,等轴g相、等轴a2相和a2/g片层之间面积分数发生变化,其变化规律主要取决于各相的Gibbs自由能变化.冷却速率对Ti-47Al-2Cr-2Nb-0.2W-0.15B和Ti-45Al-8Nb-0.2Si-0.3B合金连续冷却相变有较大的影响.对于Ti-47Al-2Cr-2Nb-0.2W-0.15B合金,水冷主要形成等轴a2相,油冷、空冷和炉冷都形成全片层组织.对于Ti-45Al-8Nb-0.2Si-0.3B合金,水冷形成a2相和gm相,油冷和空冷形成羽毛状、Widmanst?tten片层和a2/g片层混合组织,炉冷形成全片层组织.对比2种Ti Al合金连续冷却曲线可知,Nb元素的增加使得连续冷却曲线向无扩散型转变方向发展.     

电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织（英文）

对电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织进行了分析,讨论了成形过程中合金凝固和固态相变过程。结果表明,电子束选区熔化成形Ti-47Al-2Nb-2Cr合金的显微为细小的γ-Ti Al和α_2-Ti_3Al形成的片层结构,但是由于电子束选区熔化成形过程冷却速度较快和成形过程中的热循环作用,成形样品的片层晶团和片层宽度皆沿样品成形方向从上到下变大变宽。合金的凝固过程通过了β单相区,并经历L→L+β→β→β+α→α→α+γ的相变过程。为了得到均匀一致的显微组织,对电子束选区熔化成形样品进行了热处理,通过1250℃油淬后1200℃保温2 h,得到了细小均匀的片层结构组织。     

Y对Ti-45Al-6Nb合金组织结构和高温氧化性能的影响

研究了Y对电弧熔炼Ti-45Al-6Nb合金组织结构和高温氧化性能的影响。结果表明,不同Y含量的Ti-45Al-6Nb合金均主要由γ+α_2片层组织、B_2析出相和少量Y_2O_3组成,微量Y对合金的相组成没有明显的影响,但能够显著细化合金的α_2+γ片层组织。高温氧化结果表明,Y能够明显改善Ti-45Al-6Nb合金的高温抗氧化性能,且Y含量为0.3%时效果更优:Ti-45Al-6Nb-0.3Y合金在1 000℃空气中的氧化速率为3.26×10~(-2) mg~2/(cm~4·h),分别是Y含量为0.1%和0.9%时合金氧化速率的41.3%和26.1%,较不含Y合金低约1个数量级。     

热暴露后合金Ti-45Al-8.5Nb(WBY)的显微组织和拉伸性能变化

对Ti-45Al-8.5Nb(WBY)合金在700℃大气环境下分别进行了1000、1700、3000、10000h的热暴露处理.通过扫描电镜及透射电镜研究了系列热暴露对该合金组织稳定性的影响,并进行了室温拉伸测试.研究发现,Ti-45Al-8.5Nb-(WBY)合金在室温下为双态细晶组织.在热暴露1000h后,在α2+γ层片晶团内α2层片通过α2→γ相变发生了平行分解,导致层片细化,这有利于提高该合金的拉伸强度,屈服强度和塑性.在热暴露1700h后,合金开始通过α2+γ→B2(ω)相变生成B2(ω)等轴晶粒.在3000h热暴露后,从α2+γ层片晶团形成的B2(ω)等轴晶粒达到18 vol％,而且其上有针状相广泛析出.经历10000h热暴露形成的B2(ω)等轴晶粒和经历3000h形成的接近,导致该合金的强度和塑性均降低,但在10000h热暴露后,这种力学性能的降低不高于10％.     

β相区凝固的铸造γ-TiAl基合金的微观组织(英文)

采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)及差示扫描量热仪(DSC)研究Ti-43Al-4Nb铸态合金及其热处理态合金的显微组织以及相转变行为。结果表明:通过从β相区凝固的方法可以获得组织细小的铸态Ti-43Al-4Nb合金;凝固过程中γ晶能够直接从β相中形核,β相与γ相沿初始α晶界共存,有效地抑制了铸态Ti-43Al-4Nb合金晶粒的长大;Ti-43Al-4Nb合金在凝固过程中的相转变顺序为L→L+β→β→α+β→α+βr→α+γ+βr→(α2+γ)片层+γ+βr;经1250℃、16h热处理后,Ti-43Al-4Nb合金的显微组织与铸态组织相比有一定程度的粗化;由于Nb元素的充分扩散以及β相的非平衡状态,经过上述热处理过程后残余β相能够被完全消除。     

钛合金表面激光熔覆材料研究进展

研究了Ti-45Al-5Nb（at％）和Ti-45Al-5Nb-0．3Y（at％）合金的铸态显微组织。结果表明：稀土Y的添加改变了Ti-45Al-5Nb合金的铸态显微组织，促进了等轴晶粒的形成，极大地细化了晶粒；稀土Y主要富集在等轴晶粒的晶界处，并呈断续网络状分布，还有极少量的稀土呈小颗粒分布在晶粒内部；与Ti-45l-5Nb合金相比，Ti-45Al-5Nb-0．3Y合金除了γ和α2相外，还形成了富集Al和Y的富稀土 相-YAl2相；在合金凝固过程中，稀土Y能够提高TiAl合金的形核率，同时稀土Y在固液界面前沿的富集抑制了初生声相的生长，并且后者对晶粒的细化起主要作用。     

Ti-Al合金抗氧化性能的影响因素初探

研究了氧化条件、显微组织和成分对Ti-Al合金抗氧化性能的影响。结果发现,Ti-48Al-2Cr-2Nb合金在700℃和800℃下具有较好的抗氧化性能,氧化形成的氧化膜为4层结构。在800℃下恒温氧化100h后,Ti-48Al-2Cr-2Nb合金的氧化增重从低到高依次为双态组织、近片层组织和片层组织。在800℃下恒温氧化100h后,3种成分的Ti-Al合金的氧化增重从高到低依次为Ti-48Al-2Cr-2Nb、Ti-46.5Al-2.5V-1C和Ti-45Al-8Nb-0.2W-0.1B-0.1Y。具有双态组织的Ti-45Al-8Nb-0.2W-0.1B-0.1Y合金在800℃下恒温氧化100h后增重4.8g/m~2。     

电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织

对电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织进行了分析,讨论了成形过程中合金凝固和固态相变过程。研究结果显示：电子束选区熔化成形Ti-47Al-2Nb-2Cr合金的显微为细小的γ-TiAl 和 α₂-Ti₃Al形成的片层结构,但是由于电子束选区熔化成形过程冷却速度较快和成形过程中的热循环作用,成形样品的片层晶团和片层间距皆沿样品成形方向从上到下变大。合金的凝固过程通过了β单相区,并经历L → L β → β → β α → α → α γ的相变过程。为了得到均匀一致的显微组织,对电子束选区熔化成形样品进行了热处理,通过1250℃油淬后1200℃保温2小时,得到了细小均匀的片层结构组织。     

B、Y及冷却速度对Ti-47Al-2Cr-2Nb合金组织的细化作用

研究了微量元素B、Y和冷却速度对Ti-47Al-2Cr-2Nb合金组织的复合细化效果。结果表明,在水冷铜坩埚磁悬浮真空感应熔炼和Y2O3型壳精密铸造条件下,B元素能够有效细化Ti-47Al-2Cr-2Nb铸件的晶粒尺寸,使其由粗大的柱状晶变为细小的等轴晶组织,但没有起到细化片层间距的明显作用。B、Y复合细化可以在B元素细化效果的基础上进一步细化片层团尺寸,同时显著细化片层间距。在壁厚为2～20mm范围内,Ti-47Al-2Cr-2Nb-0.8B-0.3Y铸件的宏观组织均为等轴晶;且随着厚度的增加,等轴晶尺寸逐渐增大。适当降低型壳预热温度也有助于获得细小的片层组织。     

Ti-22Al-25Nb与TC11异种钛合金的线性摩擦焊接

通过Ti-22Al-25Nb(Ti2AlNb基合金)与TC11((α+β)钛合金)的线性摩擦焊接,研究焊接工艺参数对接头外貌及界面结合率的影响,观察接头附近显微组织,并测试了其显微硬度。结果表明,随着焊接工艺参数,如摩擦时间、摩擦频率和摩擦压力的提高,接头的结合率显著提高;在焊接和随后的冷却过程中,TC11合金侧的热影响区域发生了α→β→α′相变,形成的大量针状马氏体α′相使焊缝区的显微硬度值显著增大;Ti-22Al-25Nb合金侧的热影响区域主要发生了(O,α2)→B2/β相变,随着O相和α2相的减少,该区域金属的显微硬度值显著降低。在合适的工艺条件下,线性摩擦焊接Ti-22Al-25Nb合金与TC11合金能够形成质量完好的焊接接头。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.