Cu含量对Ti-Cu合金半固态可锻性及锻造后力学性能的影响（英文）

通过镦锻试验和模锻实验研究了Ti-Cu系合金半固态锻造行为,并对锻材进行了拉伸试验,讨论了Cu含量对半固态可锻性及力学性能的影响。结果表明:1000°C至1150°C半固态锻造较常规锻造具有较小的顶锻压力;其中,1000°C至1050°C间半固态锻造的Ti-Cu系合金均表现出较好的可锻性,在75%的锻造变形量下无明显缺陷。分析认为,Ti-Cu系列合金中含有较多的低熔点Ti_2Cu相,随着半固态温度升高或Cu含量的增加,材料中的液相含量增加,增加的液相含量对变形起到润滑作用,减少了固相变形引起的应力集中,有效地降低了变形抗力,改善了成形性。力学性能研究表明:半固态锻造Ti-Cu系合金较常规锻造合金强度升高,塑性降低。随着Cu含量的升高,合金的强度明显提升,塑性降低。分析认为:力学性能的变化主要是由于Ti_2Cu相析出含量、形态和分布相关,随着Cu含量和半固态温度的升高,更多Ti_2Cu相在晶内和晶界析出,引起析出强化作用,同时,晶界析出的针状Ti_2Cu相形成了偏析带,降低了合金塑形。     

半固态锻造Ti14合金的拉伸性能和组织演变特征(英文)

通过室温和高温拉伸性能测试,对比研究了Ti14合金经常规锻造(950℃)和半固态锻造(1000℃和1050℃)后试样在不同温度区间的宏观力学行为,分析了微观组织演变规律、断口微观形貌及断裂特征。结果表明:合金经半固态锻造后表现出高强度、低塑性的力学特征,随着半固态锻造温度的升高,合金力学性能下降。半固态锻造过程中组织的变化是引起力学性能差异的主要原因,而组织演变的主要特征是Ti2Cu析出相形态和分布的变化。随着半固态温度的升高,更多的液相在晶界析出,并在凝固过程中析出大量板条状Ti2Cu相,最终在晶界上形成偏析带组织。这种带状组织在拉伸过程中引发了解离断裂,导致了低塑性。此外,通过再结晶退火可以有效地细化半固态组织,改善强度性能。     

半固态变形量对Ti14合金热稳定性的影响

研究新型阻燃钛合金Ti14(α+Ti2Cu)经不同变形量(45%～75%)半固态锻造后的热稳定性能,分析变形量对合金热稳定性能的影响。结果表明:变形量改变析出相的形态及晶粒尺寸,使合金具有不同的热稳定性能。随变形量的增加,Ti14合金热暴露后的强度呈先降低后升高的趋势,塑性有所改善。半固态变形量较小时(45%),合金晶粒粗大,Ti2Cu相呈长条状分布于晶界,高的强度取决于析出相强化作用;随变形量增大(75%),晶粒细化,Ti2Cu相呈颗粒状或短棒状弥散分布,产生细晶强化,使得强度和塑性都得到改善。断口分析表明:变形量较小,断口存在大量撕裂棱;变形量达到75%,断口以韧窝为主;表明析出相和晶粒尺寸共同决定Ti14合金的热稳定性能。     

Ti14合金半固态变形组织及力学性能

以新型阻燃Ti14合金(α+Ti2Cu)为研究对象,分别进行常规固态锻造(950 ℃)和半固态锻造(1000 ℃),对比研究合金半固态变形的组织和拉伸性能,并讨论可能引发组织和拉伸性能变化的原因.结果表明:半固态锻造过程未发生动态再结晶,使得室温组织晶粒粗大,液相Ti2Cu在压力作用下沿晶界分布,形成了偏析,粗化了晶界,改变了晶界的结构;晶界结构的变化诱发了晶界的硬化效应,使得室温拉伸的强度升高,塑性降低.     

Ti14合金半固态变形的晶界偏析行为

以新型阻燃钛合金Ti14(α+Ti2Cu)为对象,研究了合金在半固态条件下的晶界偏析行为.结果表明,Ti14半固态变形使得Cu元素在晶界偏聚,冷却后以Ti2Cu相偏析于晶界,偏聚和偏析过程与半固态变形温度具有较大的相关性;同时,提出了Ti2Cu相形核和析出长大动力学模式,并用非经典形核长大理论进行了解释.     

半固态加工Ti-Cu合金的显微组织和力学行为（英文）

研究触变成形Ti-Cu合金的力学性能。Ti-Cu (25%,27%,29%Cu,质量分数)锭的制备流程为：先进行电弧熔炼,再在950℃均匀化处理24h,然后在900℃热锻,最后在1035℃热处理300 s后以8 mm/s的速度触变成形。结果显示,触变成形合金表现出良好的力学强度,但其在拉伸载荷下的塑性一般,在压缩载荷下的塑性尚可。随着Cu含量的增加,包晶Ti₂Cu相(转变液相区)的体积分数增加,与α+Ti₂Cu相区(转变固相区)相比,其力学强度和塑性更低,导致合金的力学强度和塑性降低。这些结果表明,Ti-Cu合金的力学性能和半固态加工性之间的平衡主要取决于Cu含量。     

Effect of Temperature on Segregation and Deformation Mechanism of α+Ti2Cu Alloy during Semi-Solid Forging

以新型阻燃钛合金Ti14 (α＋Ti2Cu)为对象,研究了合金在不同温度半固态锻造过程中的偏析和偏聚现象及由此导致的变形机制的变化。结果表明,半固态温度影响液相含量和分布,随着温度的升高液相在晶界由不连续分布转变为连续分布析出,并最终形成了网状结构分布。锻造过程中由于液相和应力的共同作用出现了宏观偏析现象,液相在压力作用下的流动在晶界处产生了宏观液相/固相分离现象,靠近试样中心固相离子集中;这种现象导致了锻造过程中变形机制的变化,中心区仍旧是固相粒子的塑性变形为主变形机制,靠近试样外边缘主变形机制转变为固相粒子的相对滑移,通过唯象模型对其过程进行讨论     

温度对α+Ti_2Cu钛合金半固态偏析行为和锻造机理的影响（英文）

以新型阻燃钛合金Ti14(α+Ti2Cu)为对象,研究了合金在不同温度半固态锻造过程中的偏析和偏聚现象及由此导致的变形机制的变化。结果表明,半固态温度影响液相含量和分布,随着温度的升高液相在晶界由不连续分布转变为连续分布析出,并最终形成了网状结构分布。锻造过程中由于液相和应力的共同作用出现了宏观偏析现象,液相在压力作用下的流动在晶界处产生了宏观液相/固相分离现象,靠近试样中心固相离子集中;这种现象导致了锻造过程中变形机制的变化,中心区仍旧是固相粒子的塑性变形为主变形机制,靠近试样外边缘主变形机制转变为固相粒子的相对滑移,通过唯象模型对其过程进行讨论。     

典型阻燃钛合金半固态锻造的力学特性

将典型Ti14合金在半固态进行了1次锻造成形,对锻造试样进行拉伸,研究其室温和高温的力学性能,并对拉伸断裂机理进行了分析。结果表明:不同的半固态温度和变形量对锻造试样的力学性能有明显的影响,随着温度和变形量的提高,强度增大,塑性降低,在1050℃和75%变形量时,合金强度最高;高温拉伸与室温拉伸表现出相同的趋势。随着温度的升高,拉伸断口由典型的穿晶断裂转变为沿晶断裂和穿晶断裂的混合断裂。     

时效处理对Cu-3Ti-3Ni合金组织与性能的影响

本文研究了时效处理对Cu-3Ti-3Ni合金组织与性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对Cu-3Ti-3Ni合金的组织和析出相进行了表征,并对其硬度、导电率和弹性模量进行了测试。结果表明：时效处理后析出Ni3Ti及 β''-Cu4Ti相。随着时效时间的延长,部分合金元素回溶于Cu基体,连续的亚稳定β''-Cu4Ti相向不连续的稳定Cu3Ti相转变。Ni3Ti相及β''-Cu4Ti相的析出减少了Ti原子的固溶,导致导电率升高。经过合适的时效处理,Cu-3Ti-3Ni合金中的Ni3Ti相及连续的亚稳定β''-Cu4Ti相析出完全,导致硬度升高,但时效处理对合金弹性模量影响不大。在本实验范围内,Cu-3Ti-3Ni合金的最佳时效处理工艺是 300°C时效2 h后炉冷,随后450 °C时效7 h炉冷。Cu-3Ti-3Ni合金的硬度、导电率及弹性模量分别是183 HV、31.34 % IACS (国际退火铜标准)及148.62 GPa。     

Effect of solution treatment on the hot workability of electroslag remelted Ni−Cr−Mo alloy

The effect of solution treatment on the hot workability of electroslag remelted Ni−Cr−Mo alloy was evaluated. Tensile tests were performed in the temperature range of 950 to 1200°C at a strain rate of 6.1/sec. The hot workability of this alloy appeared to be intimately dependent on the amount of precipitates that were identified as the P phase. A solution treatment at 1250°C for 2 hours induced a considerable dissolution of the precipitates. It resulted in a significant improvement in the hot workability (from 40% to 70% in RA value), giving the deformation mechanism for grain boundary sliding at below 1000°C and dynamic recrystallization at above 1100°C. The hot ductility drop at around 1050°C could be attributed to the precipitates reprecipitated especially at the grain boundary before deformation.     

Tensile properties of as-deformed 2A50 aluminum alloy in semi-solid state

Tensile properties of as-deformed 2A50 aluminum alloy were investigated in the high temperature solid and semi-solid states. The results show that temperature has almost no effect on the maximum tensile stress between 500 °C and 530 °C, and the maximum tensile stress decreases rapidly when the temperature is above 532 °C. The ductility decreases with increasing temperature and has an obvious fall when the temperature is above solidus temperature. This alloy almost has no ductility above 537 °C, and cannot sustain tensile stress above 550 °C. A brittle temperature range in which this alloy is prone to form microcracks was derived. The relation between microstructure, fraction solid and tensile properties were also investigated by examining the metallograph and fracture surface morphology of tested specimens, which could provide reference for forecasting the microcracks in this alloy occurring in semi-solid processing.     

Microstructure control and mechanical properties from isothermal forging and heat treatment of Ti–22Al–25Nb (at.%) orthorhombic alloy

The microstructural evolution, creep, and tensile deformation behavior of an orthorhombic Ti–22Al–25Nb (at.%) alloy was investigated by thermo-mechanical processing, including common forging, isothermal forging, and heat treatment. Three different microstructures were obtained by varying the isothermal forging temperatures and heat-treatment schedule. Tensile-creep experiments were conducted from 650 to 700 °C and over a stress range of 100–200 MPa. The alloy tensile strengths at room temperature and 650 °C were also determined. As the isothermal forging temperature increases from 1040 °C to 1080 °C, three alloy microstructures result, including equiaxial, duplex, and bimodal-size lamellar orthorhombic microstructures. Of the three, the bimodal-size lamellar orthorhombic microstructures have the highest strength but worst ductility, whereas the equiaxial microstructures have the highest ductility but worst strength. The equiaxial microstructures have the worst creep resistance, whereas the duplex microstructures and bimodal-size lamellar orthorhombic microstructures have a similar creep resistance.     

V-5Cr-5Ti合金的拉伸性能及其强化机理

对真空熔炼V-5Cr-5Ti合金开展了均匀化退火、热锻开坯、冷轧变形和热处理实验,利用万能试验机、扫描电镜（SEM）和透射电镜（TEM）研究了V-5Cr-5Ti合金中析出相对力学性能影响,估算了V-5Cr-5Ti合金中析出相强化的效果。结果表明：铸态V-5Cr-5Ti合金存在以片层状析出相为特征的树枝状析出相,合金均匀化退火后析出相由片层状转化为针状,由树枝状转化成团聚状。析出相在变形过程中破碎成短条状或球状颗粒。铸态合金的抗拉强度、屈服强度和延伸率的平均值分别为505.0 MPa、415.0 MPa和8.2%,断裂机制为脆性的解理断裂。均匀化热处理后断裂机制转变为沿晶断裂和准解离断裂共存的混合型断裂。80%冷变形＋热处理后合金的抗拉强度、屈服强度和延伸率的平均值分别为487.3 MPa、382.7 MPa和26.2%,由于晶粒及析出相形态的变化,合金塑性得到大幅改善。锻造和冷轧后合金断裂机制为韧性的微孔型断裂。析出相以Orowan强化机制增强V-5Cr-5Ti合金,以80%冷轧1000 ℃/1 h退火状态合金为例,由析出相强化获得的屈服强度增量约为50.1 MPa。     

Microstructural evolution and mechanical properties of forged β-solidified γ-TiAl alloy by different heat treatments

The microstructural evolution and tensile properties of a forged Ti?42Al?5Mn alloy subjected to different heat treatments were studied. The results showed that, when the forged alloy was aged at 800 °C for 24 h, the interlamellar spacing (λ) and γ grain size at colony boundaries are generally coarsened. Whereas, when the alloy was first annealed at 1300 °C and then aged at 800 °C for 24 h, this coarsening of related microstructures appears less pronounced. The suggested annealing temperatures for the forged Ti?42Al?5Mn alloy are in the range of 1250?1300 °C. It was found that, on the condition of the same annealing system, both the strength and ductility were improved as the aging temperature changed from 1000 to 800 °C. The secondary precipitated β_o (β_o,sec) at colony boundaries could be responsible for improving the strength, and the γ phase at colony boundaries with the grain size about 6 μm might be one of the main reasons for the better ductility.     

Microscopic Characterization of Semi-Solid Ti14 Alloy

采用热模拟系统研究半固态变形参数对合金微观组织演变和元素分布的影响,并讨论变形过程中的Ti2Cu析出行为。结果表明:微观组织,特别是Ti2Cu析出过程受变形参数影响较大;温度的增加,应变速率和变形量的降低将促进Ti2Cu在晶界的偏析,最终形成了网状晶界结构。分析认为:半固态晶界的析出过程主要受控于包晶反应,升温或降低其他变形参数将有利于液相在晶界的析出,形成晶界Cu元素富集区。液相的偏析和Cu元素的富集增加了该区域的包晶反应,最终在冷却过程中形成了粗大的网状晶界结构。     

The hot formability of an Al-Cu-Mg-Fe-Ni forging disk

The high temperature formability of AA2618-T61 forged disk was studied by means of tensile test over temperatures and strain rates ranging from 100 to 400°C and 3 × 10⁻⁵ −3 × 10⁻³ s⁻¹, respectively. The constitutive equations of the material were calculated based on an Arrhenius-type equation and the ductility of the material was evaluated considering elongation and percent reduction of area. The results showed that both kinds of softening mechanisms, dynamic recovery and dynamic recrystallization, occurred during high temperature deformation of the alloy. Strain rate sensitivity of the material was evaluated in all the deformation conditions and the obtained values were used to calculate the apparent activation energy.     

Microstructural banding in thermally and mechanically processed titanium 6242

Ti-6Al-2Sn-4Zr-2Mo-0.1Si coupons were shaped by repeated cycles of heating (to 954 °) and hammer or press forging followed by a solution anneal that varied from 968 to 998 °. The coupons were originally extracted from billets forged below the beta transus (1009 °) and slow cooled to ambient temperatures. Macroscopic and microstructural banding is observed in some forged and solution annealed coupons. The microstructure consists of elongated “platelets” of primary alpha. More significant banding is observed subsequent to annealing at lower temperatures (968 °), whereas subsequent to higher annealing temperatures (998 °) much less microstructural banding is present. About the same level of banding is observed in hammer forged coupons and press forged coupons. The observation of these bands is significant, because these may lead to inhomogeneous mechanical properties. Specifically, some types of banding are reported to affect the high-temperature creep properties of this alloy. Classically, banding in Ti6242-0.1Si has been regarded as a result of adiabatic shear, chill zone formation, or compositional in homogeneity. High- and low-magnification metallography, electron microprobe analysis, and micro-hardness tests were performed on forged and annealed specimens in this investigation. The bands of this study appear to originate from the microstructure that consists of the forged billet of elongated primary alpha. The deformation of the extracted coupon is neither fully homogeneous nor sufficiently substantial, and the coupon is only partly statically restored after a solution anneal. Areas not fully restored appear as “bands” with elongated primary alpha that are remnant of the starting billet microstructure. Therefore, a source of banding in Ti- 6242- O.1Si alloy additional to the classic sources is evident. This type of banding is likely removed by relatively high solution treatment temperatures and perhaps greater plastic deformation during forging.