粉末高温合金FGH96中的原始粉末颗粒边界及其对合金拉伸断裂行为的影响

采用等离子电极旋转雾化法和热等静压法(hot isostatic press,HIP)分别制备FGH96粉末与合金,对原始及高温(1 150℃)预热处理后的FGH96粉末表面析出相以及HIPed FGH96合金的原始粉末颗粒边界(prior particleboundary,简称PPB)进行分析,进而研究PPB对合金室温和750℃拉伸断裂行为的影响。研究发现:原始粉末表面无明显析出相,1 150℃预热处理后粉末表面有块状MC和细小氧化物分布;热等静压法制备的FGH96合金及其热处理后,PPB析出相主要由颗粒和块状的金属碳化物MC及富Zr的氧化物颗粒组成;该合金经过固溶和时效处理后,颗粒状MC部分溶解而块状MC长大,PPB碳化物的尺寸分布由单峰分布转变为双峰分布;常温拉伸时微孔在PPB上形成并扩展,合金沿PPB断裂;750℃拉伸时,合金强度与塑性较常温下明显降低,部分M23C6在晶界析出,块状和颗粒状碳化物部分溶解,为M23C6提供碳源,合金断口呈现沿晶和沿PPB混合断裂的形貌。     

镍基双合金扩散偶的拉伸性能研究

采用热等静压(HIP)扩散连接工艺,获得了镍基单晶高温合金与粉末高温合金的扩散偶。研究了热等静压和热处理工艺对扩散偶的组织和拉伸性能的影响。结果表明,不同温度热等静压的扩散偶均实现了冶金结合,瞬时拉伸断口位置处于DD402侧,断裂面为{111}滑移面。随着HIP温度升高,DD402母材的γ′相粒子粗化,FGH95粉末合金母材的再结晶晶粒长大;1 166℃HIP扩散偶热处理后,FGH95粉末合金的γ′相由晶界大尺寸γ′相、晶粒内中等尺寸的和细小的γ′相组成。扩散偶试样的650℃抗拉强度受HIP温度影响小,而屈服强度随着HIP温度升高而降低。     

Inconel 718高温合金SMAW焊接接头组织及力学性能研究

对Inconel 718镍基高温合金进行焊条电弧焊(SMAW)焊接试验,研究其接头显微组织和力学性能。结果表明,焊接接头由五部分组成,分别为焊缝区、细晶区、不完全再结晶区、粗晶区以及基体;由于焊缝区有大量Laves相的存在,导致焊缝区为焊接热影响最薄弱的区域,拉伸试样断裂位置在焊缝处;显微硬度测试表明焊缝区硬度最低,母材硬度最高。     

Hf和Zr对FGH96合金PPB及力学性能的作用研究

采用PREP(等离子旋转电极法)制粉+HIP(热等静压)成形工艺制备FGH96合金,研究了w(Hf)+w(Zr)分别为0.0 +0.04％、0.3％+0.04％、0.6％+0.04％和0.3％+0.06％时合金的显微组织,以及室温和800℃冲击性能,室温、650℃和750℃拉伸性能,650℃/970MPa持久性能.结果表明:FGH96合金的PPB未形成连续的网膜结构,对合金性能危害较小；适量的Hf可消除PPB组织,改善合金的高温性能,尤其能显著提高持久寿命和塑性,消除缺口敏感性；含Hf时,过量的Zr促使氧化物在粉末边界连续析出,严重降低合金持久性能.FGH96合金中,Hf、Zr的最佳含量为0.6％、0.04％.     

FGH96合金固相扩散连接界面组织与失效机制

对原始状态分别为锻态、固溶态和半时效态的FGH96合金固相扩散连接界面显微组织进行表征,并对连接界面的拉伸性能进行测试,对失效行为进行研究。结果表明,锻态、固溶态和半时效态试样经固相扩散连接后界面均实现了良好的冶金结合,连接界面无孔洞和缝隙等缺陷。锻态试样界面扩散更为充分,组织过渡更为平缓;固溶态和半时效态试样界面存在明显的连接影响区。锻态试样经固相扩散连接和标准热处理后,二次γ?相细小、均匀且呈典型椭球状;固溶态和半时效态试样因固相扩散连接热循环的作用导致γ?相发生长大和分化。二次γ?相尺寸及形貌的不同决定了界面区域性能水平的差异。电子背散射衍射测试结果表明,连接界面处大晶粒的择优取向为{100},距离固相扩散连接界面越近,晶粒的择优取向越明显。拉伸试验结果表明,锻态试样经固相扩散连接和标准热处理后,连接界面处的强度达到基体强度的99%以上。拉伸裂纹主要萌生于连接界面大晶粒及γ?相粗化聚集区域,体现为穿晶的韧窝型断裂。     

室温大气环境下欠时效态3J21合金的拉伸性能

在万能拉伸试验机上对室温大气环境下欠时效态3J21合金的拉伸性能进行研究,并采用金相显微镜、X射线衍射仪对欠时效态金相组织及物相进行分析,采用TEM对固溶态、欠时效态试样及拉伸断口附近形变的显微组织进行分析,采用扫描电镜（SEM）对拉伸断口进行观察。结果表明,室温大气环境下欠时效态3J21合金的拉伸断口为韧窝断口,断口附近显微组织中滑移线之间的距离较小。欠时效态3J21合金具有较好的强度和塑性配合。同时讨论了室温大气环境下欠时效状态对3J21合金拉伸性能的影响。     

WEL-TEN780A高强钢及焊接接头疲劳裂纹扩展速率

依据GB6398-86采用紧凑拉伸试样（CT），对WEL-TEN780A钢及其用L-80SN焊条手工电孤焊焊接接头的焊缝和热影响区的疲劳裂纹扩展速率进行了研究，结果表明：在相同的疲劳循环载荷作用下，热影响区疲劳裂纹扩展速率高于母材和焊缝，焊缝金属具有最低裂纹扩展速率。焊缝金属中的针状铁素体细小且被大角度晶界所分割，疲劳裂纹扩展时要消耗更大的能量，从而降低裂纹扩展速率，成为止裂型焊缝。     

粉末粒度和氧含量对HIP态FGH96合金组织的影响

对氩气雾化法制备的高温合金FGH96粉末进行了热等静压(HIP)处理,分析了粉末粒度和氧含量对HIP态合金组织的影响,研究了FGH96合金组织中PPB的类型、相结构和形成机制。结果表明,氩气雾化FGH96粉末的氧含量较低,平均氧含量约为50×10-6,随着粉末粒度降低,颗粒比表面积增大,促进了粉末氧含量的升高;粉末经HIP处理后氧含量具有遗传特征,原始粉末氧含量越高,HIP态合金氧含量也越高,且平均氧含量增至83×10-6;粉末尺寸和氧含量对合金致密化行为无明显影响,HIP态合金密度约为8.33 g·cm-3。小尺寸粉末制备的HIP态合金原始颗粒边界主要析出ZrO2和MC碳化物,而大尺寸粉末制备的HIP态合金原始颗粒边界主要析出大尺寸花瓣状γ’相和少量MC碳化物。粉末粒度和氧含量影响PPB析出,小尺寸粉末因氧含量高经HIP处理时颗粒边界处存在更多、尺寸更大稳定的ZrO2,ZrO2成为MC碳化物析出形核的核心,促进了大量MC碳化物的析出。     

20MnSiV Ⅲ级钢筋焊缝和热影响区拉伸脆性断裂的分析

分析了Φ32mm20MnSiVⅢ级钢筋搭接焊试样拉力试验断口—焊缝和热影响区脆性断裂。断口处HV硬度试验和扫描电镜观察表明，焊缝和热影响区存在大量魏氏组织和贝氏体,马氏体是拉伸脆性断裂的主要原因，夹杂物向晶界偏聚导致沿晶脆性断裂，小热量输入多道焊接可改善热影响区的组织和韧性。     

Ti-600合金热暴露前后室温拉伸性能及变形机制研究

研究了Ti-600合金镦制饼材600℃热暴露前后室温拉伸性能与组织的变化,并分析了其室温拉伸变形机制。研究结果表明,600℃热暴露100 h后,毛坯热暴露试样的强度较热暴露前的固溶时效试样(STA)提高了3%左右,延伸率的保持率为81.1%;试样热暴露试样的强度稍有降低,延伸率的保持率仅为55.6%。600℃热暴露100 h前后,Ti-600合金镦制饼材的组织变化不明显,热暴露后其原始β晶粒尺寸较之前的稍有长大。STA状态下晶界与板条较平直,热暴露后少数板条弯曲,并且板条较短较细小。试样热暴露试样组织内的α相与β板条比毛坯热暴露试样的粗大。经分析,Ti-600合金热暴露前后室温拉伸变形时主要的变形机制是位错穿越α束滑移以及位错柱面滑移。     

Precipitation of μ Phase in Nickel-based Powder Metallurgy Superalloy FGH97

The precipitation behavior of topological close-packed(TCP)μphase in powder metallurgy(P/M)nickelbased superalloy FGH97 was investigated.The results showed that proper addition of solution strengthening elements,such as Co,Cr,W,Mo,improved tensile strength,while excessive addition of those elements facilitated the precipitation ofμphase,which seriously aggravated the plasticity of the P/M superalloy.For the heat-treated specimens,the relationship between critical aging time(whenμstarted to precipitate),aging temperature,and the average electron vacancy number ofγmatrix was established.     

粉末高温合金FGH97疲劳裂纹扩展行为

测定不同晶粒尺寸、γ'相以及不同Hf含量的粉末高温合金FGH97在650℃高温条件下的疲劳裂纹扩展速率,并将其与FGH95和FGH96两代粉末合金的疲劳裂纹扩展速率进行对比.用定量分析的方法对FGH97合金在疲劳断裂各个阶段的行为特征进行分析.较大晶粒尺寸的FGH97合金具有较低的裂纹扩展速率,合理的二次和三次γ'相匹配析出,可以获得较高的疲劳寿命;Hf元素的添加使合金的整体疲劳寿命增大;FGH97合金与FGH95和FGH96相比,具有较高的疲劳裂纹萌生抗力,更低的高温疲劳裂纹扩展速率.      

Microstructure, Tensile Properties and Heat Treatment Process of Spray Formed FGH95 Superalloy

 The potential of spray forming for microstructural refining can be attractive to the production of superalloys. A 200 mm spray formed FGH95 superalloy round billet that was produced using a single atomizer has considerably homogeneous, small, equiaxed grains. The measured oxygen content is 2×10-5, and the measured porosity is only 0. 6%. The achieved yield of deposit is in a good range of about 73. 6%. The microstructure and tensile properties of nickel-based spray formed FGH95 superalloy are analyzed. Also, effects of heat treatment on microstructure were discussed. The results show that the spray formed FGH95 superalloy has higher isotropy in tensile property due to its γ′ phase homogeneous distribution and less defects in the microstructure. Regarding processing procedures, the different heat treatment processes affect the microstructure and γ′ phase homogeneous distribution of spray formed FGH95 superalloy.     

FGH4102粉末高温合金等温热模拟压缩试验及动态再结晶组织研究

本文研究了新型第四代粉末高温合金FGH4102在等温热模拟压缩过程中的组织演变,对γ′相在动态再结晶过程中的作用进行了探讨。结果表明,热等静压态合金在1 060～1 120℃温度范围变形时,热加工性能较好。1 140℃变形后试样容易发生开裂,合金热加工性能较差。合金在γ+γ′两相区变形时均发生了不同程度的动态再结晶,再结晶晶粒尺寸远小于热等静压态的晶粒尺寸。变形过程中,尺寸较大的γ′相起到促进动态再结晶的作用。变形参数对动态再结晶的影响非常显著。低温高应变速率变形时,γ′相促进动态再结晶形核占主导地位,再结晶晶粒比较细小;高温低应变速率变形时,晶粒长大逐渐占据主导地位,再结晶晶粒尺寸较大。     

粉末高温合金Udimet720Li γ′强化相析出行为

采用气淬炉模拟了粉末高温合金Udimet720Li经空冷、风冷及油冷等不同冷却路径的固溶处理过程,测试了经过两级时效处理的合金在650 ℃的拉伸性能,研究了拉伸变形后的位错组态,分析了冷却速率对γ′强化相析出规律及力学性能的影响。结果表明:粉末高温合金Udimet720Li的析出相强化机制为位错切过机制,二次γ′相尺寸越小,合金强度越高。合金二次γ′相的形核析出温度区间为900～1000 ℃,其尺寸与合金在该温度范围内的冷却速率成反比,冷却速率越大,γ′相尺寸越小,当冷速高于100 ℃/min时,合金强度达到应用要求。推荐粉末Udimet720Li合金盘件固溶处理的冷却方式为:在1000 ℃以上保持低冷却速率来降低淬火应力,然后选择油浴作为盘件淬火的冷却方式,入油温度应在1000 ℃左右。     

长期时效对FGH95镍基粉末高温合金γ'相及晶格常数的影响

在不同温度下对FGH95镍基粉末高温合金进行长期时效处理,通过合金显微组织观察和X射线衍射分析,研究了长期时效对FGH95合金γ'相及晶格常数的影响。结果表明,完全热处理FGH95合金经450和550℃长期时效后,合金中细小γ'相略有长大,其粗化行为符合Lifshitz,Slyozov和Wagner（LWS）粗化动力学理论;随着时效时间的延长,FGH95合金中γ'相的晶格常数有所增加,而γ和γ'两相的晶格错配度减小;与时效时间相比,时效温度对FGH95合金中γ'相尺寸及晶格常数的影响更大。     

Mechanical Behavior of Three-Dimensional Braided Nickel-Based Superalloys Synthesized <Emphasis Type="Italic">via</Emphasis> Pack Cementation

Braided tubes of Ni-based superalloys are fabricated via three-dimensional (3-D) braiding of ductile Ni-20Cr (wt pct) wires followed by post-textile gas-phase alloying with Al and Ti to create, after homogenization and aging, γ/γ′ strengthened lightweight, porous structures. Tensile tests reveal an increase in strength by 100 MPa compared to as-braided Ni-20Cr (wt pct). An interrupted tensile test, combined with X-ray tomographic scans between each step, sheds light on the failure behavior of the braided superalloy tubes.     

C元素对FGH96粉末高温合金显微组织和力学性能的影响

对C质量分数分别为0.05%和0.09%的FGH96合金进行了显微组织和力学性能的分析。结果发现:C元素含量较高时,除了碳化物数量明显增多外,还会在晶界处形成较大尺寸的块状MC碳化物;但是,C元素含量并未对原始颗粒边界(prior particle boundary,PPB)、晶粒度及γ′相产生明显的影响。C元素含量较高会提高FGH96合金在650℃时的抗拉强度和屈服强度,但会降低其塑性。在低周疲劳试验中,C元素含量较高,形成的大块MC型碳化物分布于表面或亚表面,将会作为裂纹起源从而显著降低合金的低周疲劳性能。     

Microstructure and Properties of an Advanced Nickel-base PM Superalloy

The need for nickel-base powder metallurgy （PM） superalloy turbine discs is becoming increasingly evi dent. With the eventual aim of improving thrust-to-weight ratio of aeroengines for power generation, well integration of significantly high strength, high damage tolerance and high-temperature capability would be reasonably required. An advanced PM superalloy, which was designed for applications up to 815- 8 5 0 ℃, was experimentally investigated. Emphasis was primarily put on microstructure and mechanical properties. The results indicated the measured phases in the sample were composed of γ,γ＇, MC, and Ma B2. With uniform coarse grain microstruc ture （ASTM 5-6）, the sample appeared to exhibit overwhelming superiority over the prior art materials FGH95, FGH96, FGH97 and FGH98. The dominant embodiments consisted of high tensile strength （Rm = 1000 MPa and Rp0.2 800 MPa at 850℃）, strong creep resistance （ξp 0.12% at 815 ℃/400 MPa/50 h）, and considerable stressrupture life （τ=457.4 h at 815 ℃/450 MPa）. The technical practicability of applications up to 815-850 ℃ of this alloy was conclusively proved.     

Alloy Composition Screening for Ni-Base Turbine Disc Superalloys Using the Creep Property of Single Crystal

This paper proposes a method for alloy composition screening using the creep property of a single crystal (SC) for designing new Ni-base powder metallurgy (P/M) turbine disc superalloys. A commercial Ni-base disc alloy, U720Li®, a Ni-Co-base disc alloy, TMW-4M3, and a Ni-base conventionally cast alloy, TM-47, were selected for investigation. Their SC and P/M samples were prepared such that their γ/γ′ structures were similar. Moreover, tensile creep tests were performed on SC samples, and compressive creep tests were performed on SC and P/M samples. The tensile creep test results of SC samples at 1073 K (800 °C) and 735 MPa indicate that 0.2 and 1 pct creep times, as well as rupture life, are long in the order of TM-47 SC, TMW-4M3 SC, and U720Li SC. These results simulate the intragranular creep resistances of the corresponding P/M alloys. Furthermore, there is no significant difference in 0.2 and 1 pct compressive creep times between the SC and P/M samples of each alloy. Additionally, the 0.2 and 1 pct creep times of tensile and compressive creep tests of every alloy had an identical order. Therefore, alloy composition screening using SC creep property enables the design of new disc alloys with excellent creep resistance.