γ-TiA1/TC4复合板材的制备及组织性能研究

提出了制备γ-TiAl/Ti合金复合板材的技术思想.采用包套轧制技术在1150 ℃轧制出厚度为3 mm的Ti-43Al- 9V-0.3Y/Ti-6Al-4V复合板材,其中Ti-43Al-9V-0.3Y合金层的厚度约为2.3 mm,Ti-6Al-4V合金层的厚度约为0.7 mm.复合板材的总变形量为80%.包套轧制后板材外形完整、无应力开裂.分析表明,复合板材的界面相主要由α2-Ti3Al构成.拉伸性能测试结果表明,随着Ti-6Al-4V合金层厚度的增加,复合板材室温下的抗拉强度、延伸率都得到了显著的提高.当Ti-6Al-4V合金层厚度达到0.7 mm时(板材总厚2 mm),室温强度和延伸率分别超过800 MPa和4%,700 ℃条件下延伸率超过25%.     

锻造与轧制对Ti-43Al-9V-0．3Y合金显微组织和力学性能的影响

铸态Ti-43Al-9V-0.3Y合金由γ相及少量α2,B2和YAl2相组成,为细小的近层片组织,晶粒(层片团)尺寸约为80 μm,层片体积分数约为85%;锻态合金由大量细小的动态再结晶等轴γ晶粒组成,组织细化显著,γ再结晶晶粒尺寸约为1-5 μm;轧态合金为细小近,γ组织,γ品粒尺寸约为20 μm,尺寸细小的B2相呈网络状分布在γ晶粒周围.铸态合金在室温下的拉伸断裂强度约为510.6 MPa,延伸率约为0.5%;在700℃下的拉伸断裂强度约为425.8 MPa,延伸率约为5.7%.锻造和轧制后的Ti-43Al-9V-0.3Y合金的力学性能均得到了明显改善.     

Microstructure-tensile properties-processing technology relationships of Ti-43Al-9V-0.3Y alloy

铸态Ti-43Al-9V-0.3Y合金由γ相及少量α2, B2和YA2相组成, 为细小的近层片组织, 晶粒(层片团)尺 寸约为80 um, 层片体积分数约为85　%; 锻态合金由大量细小的动态再结晶等 轴γ晶粒组成, 组织细化显著, γ再 结晶晶粒尺寸约为1-5 um; 轧态合金为细小近γ组织, γ晶粒尺寸约为20um, 尺寸细小的B2相呈网络状分布在γ晶粒周围. 铸态合金在室温下的拉伸断裂强度约为510.6 MPa, 延伸率约为0.5%; 在700 ℃下的拉伸断裂强度约为425.8 MPa, 延伸率约为5.7%. 锻造和轧制后的Ti-43Al-9V-0.3Y合金的力学性能均得到了明显改善.     

锻态Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴及片层组织高温拉伸性能及组织演变

等轴γ晶粒和α2/γ片层是beta-gamma TiAl合金的2种主要变形组织形态。研究了锻态Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴组织及片层组织的高温拉伸性能及组织演变。结果表明:拉伸温度对Ti-44Al-4Nb-4V-0.3Mo-Y合金的力学性能和显微组织有显著的影响。在相同温度下,Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴组织的抗拉强度和屈服强度略高于片层组织,而延伸率相差不大。随拉伸温度的升高,合金的抗拉强度和屈服强度逐渐减小,而延伸率迅速增大。对于等轴组织,提高温度,等轴γ晶粒被拉长,发生完全的动态再结晶,从而细化合金的显微组织。对于片层组织,α2/γ片层的分解和γ板条的再结晶程度随拉伸温度的升高而增大。Ti-44Al-4Nb-4V-0.3Mo-Y合金的韧脆转变温度在750～800℃之间。     

碳对粉末冶金Ti-46.6Al-1.4Mn-2Mo的组织细化和力学性能改善

主要由基体γ相和少量α2相组成的TiAl金属间化合物，具有优良的比强度、抗氧化性和抗蠕变性，被用作轻型高温结构材料，主要用于汽车业和航空领域。人们已开发出多种技术，改善和提高TiAl合金的力学性能。比如，通过控制片层团及片层的尺寸和形貌，设计片层间距来优化TiAl合金全片层组织(α2及γ板条交替排列)，达到提高TiAl合金的断裂韧性的目的。在TiAl合金中，间隙原子由于可改变片层间距，从而影响合金性能，而受到广泛关注。韩国学者通过添加碳而细化Ti-46.6Al-1.4Mn-2Mo合金组织来获得最佳力学性能。实验合金名义成分为Ti-46.6…     

Ti/TiAl复合板大压下率热轧复合行为及组织性能研究

采用大压下率包套热轧法成功制备了界面无缺陷的Ti-6Al-4V(质量分数,%)/Ti-43Al-3V-2Cr(原子分数,%)复合板,并对复合板的显微组织和力学性能进行了研究。结果表明,界面区域无明显缺陷,成功避免了Kirkendall现象。复合板界面厚度约为230μm,根据相组成不同,可将界面分为2个区域,其中1区域为近Ti-6Al-4V合金界面处,主要由α/α₂+β/B2组成;界面2区域为近TiAl合金界面处,主要由α/α2+β/B2+γ组成。界面区域组织是由于Ti-6Al-4V合金中Ti元素扩散到TiAl合金层以及TiAl层的Al和Cr元素扩散到Ti-6Al-4V合金层所致。测试了复合板的界面维氏硬度和不同加载方式的三点抗弯强度。结果表明,界面1区域具有最高的显微硬度,横向试件垂直表面加载时复合板表现出最佳的抗弯能力,抗弯强度达到1150.82 MPa。基体和界面区域均为脆性断裂,界面结合处未发生断裂。     

包套锻造对Ti-45Al-5.4V-3.6Nb-0.3Y

采用水冷铜坩埚真空感应熔炼技术制备名义成分为Ti-45Al-5.4V-3.6Nb-0.3Y(摩尔分数,%)的高质量合金铸锭,采用XRD、OM、SEM及TEM等分析手段分析研究该合金的组织演变过程,同时进行力学性能测试.结果表明:Ti-45Al-5.4V-3.6Nb-0.3Y合金具有近层片组织结构,由γ、α2和β三相组成;经包套锻造处理后,合金的晶粒尺寸显著减小,由100 μm下降至7 μm左右;合金的室温屈服强度提高220 MPa左右,达到620 MPa,室温伸长率提高到1.08%;经700 ℃处理后,该合金的屈服强度从562 MPa升高到708 MPa,伸长率从7.6%提高到35.55%.     

放电等离子烧结制备高铌TiAl合金

以Ti-45Al-8．5Nb-0．2B-0．2W-0．1Y合金粉末为原料,采用放电等离子烧结工艺制备了高铌TiAl合金。结果表明,当烧结温度高于1000℃时,可制备出致密度高、组织均匀的高铌TiAl合金;烧结温度对合金的显微组织影响显著,通过改变烧结温度可得到具有近γ（NG）、双态（DP）、近片层（NL）、全片层（FL）4种典型组织的高铌TiAl合金：合金的室温力学性能与显微组织密切相关,当烧结温度为1100℃时,所制备合金显微组织为细小双态组织,其抗拉强度为1024MPa,延伸率为1．16％,显示出较好的室温力学性能。     

Ti/Al摩尔比对铸造TiAl合金组织及力学性能的影响

以Ti-46.5Al-2.5V-1.0Cr合金为基础,研究了Ti/Al摩尔比的变化对合金组织及力学性能的影响.采用真空感应悬浮炉离心浇注制备了规格为100mm×65mm×10mm的TiAl试片.组织观察发现Ti/Al摩尔比为1.032和1.075时,都得到了柱状晶组织,后者组织更整齐,a2/γ层片取向一致性增强;摩尔比为1.121时,组织变成等轴晶组织,由粗大的全层片组织组成.对3种合金进行拉伸试验,发现Ti/Al摩尔比从1.075降低到1.032时,抗拉强度提高到600MPa,伸长率为1.0%;Ti/Al摩尔比提高到1.121时,其抗拉强度下降到440MPa.     

Ti-45Al-5Nb(-0.3Y)合金的连续冷却相变规律

冷却速度对Ti-45Al-5Nb和Ti-45Al-5Nb-0.3Y合金连续冷却相变有较大的影响.炉冷形成全层片组织,空冷下层片形成被α→γm块状反应抑制,油冷形成了极细小的层片组织,水冷主要发生了α→α2有序化转变.空冷导致了羽毛状组织消失和α2相的增加,水冷导致α2晶界的细小层片晶团尺寸较小、数量较多.Y添加对Ti-45Al-5Nb合金连续冷却相变有较小的影响.     

Microstructure and mechanical properties of large size Ti-43Al-9V-0.2Y alloy pancake produced by pack-forging

A pancake of Ti-43Al-9V-0.2Y (at.%) alloy with dimensions of ϕ480 mm × 46 mm was fabricated by pack-forging with a thick reduction of 80%. The as-forged Ti-43Al-9V-0.2Y alloy pancake has a duplex (DP) microstructure, which is composed of B2/α₂/γ lamellar colonies and massive B2 and γ phase regions distributed along the boundaries between the lamellar colonies. Different microstructures were obtained by heat treatment of samples cut from the as-forged Ti-43Al-9V-0.2Y alloy pancake. A fully lamellar (FL) structure consisting of B2/α₂/γ lamellar colonies was obtained after the heat treatment of 1350 °C/8 h. Tensile test results exhibited that the yield strength (YS) and ultimate tensile strength (UTS) of the alloy with DP microstructure were decreased from 680.7 MPa to 834.3 MPa at room temperature to 589.5 MPa and 693.1 MPa at 700 °C, respectively, and the elongation (δ) of the alloy with DP microstructure was increased from 1.99% at room temperature to 12.12% at 700 °C; the elongation (δ) of the alloy with FL microstructure was increased from 1.52% at room temperature to 85.84% at 800 °C.     

Microstructure and properties of a beta-solidifying TiAl-based alloy with different refiners

This study systematically compared the influences of yttrium(Y),boron(B),and carbon(C) on the microstructural refinement and properties of a Ti-43Al-5Nb alloy.The microstructural refinement effect in the TiAl alloy closely depends on the refiner used.The refinement effects of the three elements on colony size and lamellar thickness can be arranged as B Y C and Y C B,respectively.Moreover,a microstructure with a small grain size and ultra-fine lamellar spacing can be obtained by adding B and Y or B and C.The mechanical properties of TiAl alloy are also influenced by the refiners.TiAl alloys with proper B and Y contents exhibit favorable hot workability,tensile properties,and fracture toughness,whereas the C-containing alloy displays poor tensile properties and low fracture toughness.These results indicate that Y and B are more suitable microstructure refiners than C.This study may serve as a reference for practical alloying design.     

Microstructure and fracture toughness of a β phase containing TiAl alloy

Microstructures and fracture toughness of Ti-45Al-2Nb-1.5V-1Mo-0.3Y alloy have been investigated. The alloy exhibits fine nearly lamellar microstructures, consisting mainly of fine lamellar grains, together with mixtures of γ and residual β phases along lamellar colony boundaries. Precipitation of both β and γ phases from α₂ lamellae was found after aging at 950 °C for 48 h. Phase transformations involving β phase both in α₂ laths and along colony boundaries are discussed. This TiAl alloy possesses a higher K_IC value up to 23.5 MPam^1/2 at room temperature, compared with fully lamellar Ti-45Al-5Nb-0.3Y alloy. The toughening mechanism for current alloy is concluded as trans-lamellar fracture, ligament bridges and crack deflection, together with precipitation of β and γ phases. The precipitation of fine β and γ particles is considered as intrinsic toughening mechanism, because α₂/β and α₂/γ interfaces generating due to precipitation can restrict dislocation motion effectively.     

Effects of minor yttrium addition on hot deformability of lamellar Ti-45Al-SNb alloy

The effects of 0.3%（molar fraction, the same below） yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloy were investigated by simulated isothermal forging tests. The ingots with the nominal compositions of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y were prepared by induction skull melting. Simulated isothermal forging tests were conducted on Gleeble 1500D thermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of 1 100, 1 150, 1 200 ℃ and strain rates of 1.0, 0.1, 0.01 s^-1. The results show that yttrium addition remarkably improves hot deformability of Ti-45Al-5Nb alloy. An appropriate hot deformation processing parameter of Ti-45Al-5Nb-0.3Y alloy is determined as 1 200 ℃, 0.01 s^-1. The flow stresses are decreased by yttrium addition under the same compressive conditions. The activation energies of deformation Q are calculated as 448.6 and 399.5 kJ/mol for Y-free and Y-containing alloys, respectively. The deformed microstructure observation under 1 200 ℃, 0.01 s^-1 condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamic recrystallization. The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by yttrium addition should be attributed to that the smaller the original lamellar colonies, the lower the deformation resistance and activation energy of deformation are, and the more the dynamic recrystallization is.     

热处理对吸铸TiAl基合金铸件组织的影响

利用金属型底浇式真空吸铸技术和添加合金元素获得TiAl基合金薄板,观察并研究薄板热处理前后的组织。结果表明,在金属型强制冷却和添加合金元素的共同作用下,利用金属型底浇式真空吸铸技术获得的TiAl基合金薄板件铸态组织细小、致密。其中Ti-47Al-5Nb-0.5Si和Ti-47Al-2W-0.5Si合金的铸态平均晶粒多在20μm左右,但是,铸态组织的片层组织不均匀,且在组织内部存在较大的偏析。将试样加热到1300℃,保温5 h,随炉冷却热处理后,TiAl基合金薄板的铸态组织有所长大,但是片层更加平整稳定,偏析也明显得到改善。     

Microstructural control and mechanical properties of dual-phase TiAl alloys

This paper summarizes our recent work on the effects of microstructural features on the mechanical properties of TiAl alloys prepared by powder and ingot metallurgy. TiAl alloys based on Ti-47Al-2Cr-2Nb (at%) were alloyed with small amounts of Ta, W, and B additions for control of alloy phases and microstructure. The alloys were processed by hot extrusion above and below T, followed by short- and long-term heat treatments at temperatures to 1350 °C in vacuum. The microstructural features in the lamellar structures were characterized by metallography, SEM and TEM, and the mechanical properties were determined by tensile tests at temperatures to 1000 °C. The tensile elongation at room temperature is mainly controlled by the colony size, showing an increase in ductility with decreasing colony size. The yield strength, on the other hand, is sensitive to the interlamellar spacing. Hall-Petch relationships hold well for both yield strength and tensile elongation at room and elevated temperatures. TiAl alloys with refined colony size and ultrafine lamellar structures possess excellent mechanical properties for structural applications at elevated temperatures.     

不同SPS烧结温度Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微组织及力学性能(英文)

采用高能球磨和放电等离子烧结(SPS)技术,制备成分为Ti-45Al-5.5(Cr,Nb,B,Ta)的TiAl合金块体,随后对TiAl合金进行热处理。研究在不同SPS烧结温度下制备的TiAl合金经过热处理后的显微组织和力学性能。结果表明:高能球磨后的合金粉末形状不规则,粉末颗粒尺寸大约为几十微米。XRD分析表明,机械球磨后的粉末由TiAl和Ti3Al两相组成;烧结后的Ti-45Al-5.5(Cr,Nb,B,Ta)合金块体主要是TiAl相,以及少量的Ti3Al和TiB2相。当烧结温度为900°C和1000°C时,合金的显微组织为双相结构,并伴随有一些细小的等轴γ晶粒和细小的针状TiB2相。当烧结温度从900°C上升到1000°C时,Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微硬度变化不大,抗压强度从1812MPa提高到2275MPa,压缩率从22.66%增加到25.59%,合金的断裂方式为穿晶断裂。     

Microstructure characterization and tensile properties of β phase containing TiAl pancake

The microstructure and tensile properties of Ti-44Al-6V-3Nb-0.3Y (at.%) alloy after canned forging were investigated. SEM results showed that the TiAl pancake exhibits inhomogeneous microstructure, which can be ascribed to the temperature drop and friction between billet and outer pack during forging, as well as the intrinsic anisotropy of lamellar colony. By means of TEM observation and EBSD analysis, the microstructure in the dominant area of the pancake was further characterized. This deformation area consists of 87.7% content of γ grains plus some refined lamellar colonies and the rest of B2 grains. The grain size ranges between 1 μm and 8.5 μm. High-angle boundaries dominate the deformation microstructure, several substructures and twins are observed as well. Additionally, current forged alloy exhibits excellent high temperature tensile strength and noteworthy yield stress anomaly (YSA), with ultimate tensile strength 680 MPa and yield strength 620 MPa at room temperature, increasing to 850 MPa and 750 MPa at 700 °C, respectively. The anomalous strengthening of current TiAl alloy is temperature dependent and can be interpreted by the dislocation cross-slip pinning mechanism.     

微量Zr对铸造TiAl合金高温力学性能的影响

在Ti-47.5Al-2.5V-1.0Cr合金中添加0.2at.％Zr以研究微量Zr对铸造形成的定向层片组织高温力学性能的作用.结果表明,添加0.2at.％Zr显著提高了该合金的持久寿命,但未对其高温拉伸强度产生明显影响.根据两种合金持久试验前后组织对比观察的结果提出,添加微量Zr主要是通过增加定向层片组织的热稳定性而使其持久性能得以改善;另外,微量Zr减少了热等静压过程中等轴晶粒的析出,也有助于延长合金的持久寿命.     

Precision casting of Ti-15V-3Cr-3Al-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured. The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al- 3Sn alloy were studied.