选区激光熔化FGH4096高温合金的组织与性能

以等离子旋转电极法制备的FGH4096粉末为原材料,利用选区激光熔化(selective laser melting,SLM)技术制备了FGH4096合金,合金致密度达99. 3%。研究了SLM沉积态、直接时效态、固溶+时效态的组织和拉伸性能。SLM沉积态FGH4096合金由柱状晶构成,垂直熔池边界生长,柱状晶内排列着精细的树枝结构或等轴结构,以奥氏体γ相为主,少量的γ′相和碳化物沿树枝结构和等轴结构边界析出;直接时效处理后,大量三次γ′相析出,树枝结构或等轴结构边界粗化;固溶+时效后,回复和再结晶的发生,合金晶粒呈不规则形状,树枝结构和等轴结构消失,少量一次γ′相和碳化物在晶界析出,晶内分布少量二次γ′和大量均匀的三次γ′相。SLM沉积态FGH4096室温拉伸塑性好,热处理后强度明显提高,塑性下降,直接时效态屈服强度和拉伸强度最高,接近锻造状态。3种状态拉伸断口呈穿晶断裂,随着强度的提高,直接时效态拉伸断口出现数量较多的沿晶断裂区域。     

时效处理对一种新型粉末高温合金组织和性能的影响

对一种新型粉末高温合金进行不同时效处理,观察析出相和显微组织,测试合金室温、高温(750、815℃)拉伸和高温(750℃/750 MPa、815℃/450 MPa)持久性能,分析不同时效处理对合金组织和性能的影响。结果表明:过高的二级时效温度导致γ′相发生Ostwald熟化,减弱了γ′相的强化效果,导致合金的室温、高温强度降低,持久寿命明显缩短。单纯的一级时效,导致二次γ′相未发生进一步长大,三次γ′相微量析出,合金的强度提高,高温塑性显著降低。试样经HT2制度热处理后,二次与三次γ′相匹配良好,γ′相尺寸适当,未发生熟化,强度略有降低,塑性明显提高,综合力学性能优异。     

淬火转移时间对油淬热处理FGH4095合金制件组织与力学性能的影响

采用不同淬火转移时间对热等静压+挤压+等温锻造工艺制备的FGH4095合金进行固溶淬火处理，并对处理后的合金进行显微组织分析与力学性能测试。结果表明，淬火转移时间对合金的晶粒组织、一次γ′相和三次γ′相的影响不大，但会影响二次γ′相的尺寸分布。淬火转移时间30 s的FGH4095合金二次γ′相的平均尺寸为142.9 nm，淬火转移时间40 s的FGH4095合金二次γ′相的平均尺寸为161 nm。淬火转移时间越短，合金的淬火冷速越快，析出的二次γ′相平均尺寸越细小。淬火转移时间30 s的FGH4095合金室温屈服强度优于淬火转移时间40 s的FGH4095合金，室温抗拉强度二者相近；淬火转移时间30 s的FGH4095合金的650℃屈服强度、抗拉强度、持久寿命以及持久塑性均高于淬火转移时间40 s的FGH4095合金。淬火转移时间越短，合金中二次γ′相的数量越多，尺寸越小，阻碍位错运动的临界剪切应力越高，使得合金的拉伸强度更高，持久寿命更长。     

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。     

热处理工艺对GH4706合金显微组织与力学性能的影响

为掌握热处理工艺对GH4706合金组织性能的影响规律,研究了A、B、MST三种热处理工艺与合金组织性能的相关关系.结果表明,GH4706合金的主要强化相为γ＇相与γ＇/γ″共析出相,η相附近易形成γ＇、γ″相贫化区.A工艺在中间时效阶段析出的大尺寸γ＇相与时效阶段析出的小尺寸γ＇/γ″共析出相能够起到错配强化的效果,增大合金的室温拉伸强度.室温下η相为脆性相,不利于室温拉伸塑性与冲击韧性,因而B工艺的室温塑性与冲击韧性最佳.高温下η相能够起到协调晶内与晶界变形的作用,提高合金的650℃/690 MPa持久寿命与塑性,但过量η相析出不利于合金的持久寿命.     

铼对定向合金组织和性能的影响

以一种定向合金为基础成分，加入不同含量的Re，采用定向凝固工艺浇注性能试棒，通过SEM研究了含Re合金的微观组织特征及Re在不同相中的分布情况，比较了不同Re含量的室温拉伸和高温持久性能。研究结果表明：通过加入Re可以有效提高合金的室温拉伸屈服强度和高温持久寿命，但室温和高温塑性有所降低。加入Re后合金的铸态组织变化不大：γ γ′共晶相数量随Re含量的增加而略有增多，并且尺寸变小。Re主要分布于γ基体中，在强化相γ′中的分布很少，并通过在γ基体中阻碍位错运动有效提高合金的高温强度。     

Ti60合金板材电子束焊接接头组织性能研究

研究了Ti60合金板材电子束焊接接头的显微组织与力学性能.研究表明,焊接接头熔合区中的显微组织由针状α′相、α相和β相组成,热影响区的显微组织为β相转变组织、针状α′相及部分未溶解的等轴初生α相组成的混合组织.焊接接头硬度呈不均匀分布,焊缝熔合区的硬度最高,热影响区次之,母材区最低.焊接接头的室温和高温拉伸均断裂于母材区,焊接接头处拉伸强度等同于接头处母材区的强度.焊接接头的持久断裂均发生于焊缝区域,接头的持久寿命均100 h.     

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。     

热处理制度对粉末高温合金性能的影响

对比研究了FGH95合金在不同热加工工艺和热处理制度下γ′相的分布，观察了不同热处理制度处理后合金的组织及时效后小γ′相的中心暗场像相，测试了室温（20℃）和高温（650℃）下材料的拉伸性能，并对高温（650℃）瞬时断裂区断口进行了对比分析。结果表明：相同热处理工艺，热等静压温度较高时，时效析出的γ′相尺寸大；不同热处理制度能改变γ′相的分布，盐浴冷却明显增大中等尺寸γ′相数量和合金的高温塑性。     

钛对GH150合金组织和性能的影响

采用金相显微镜、透射电镜、化学相分析和力学性能测试等方法，研究了钛含量对ＧＨ１５０合金组织和性能的影响。结果表明，在１．６３％～２．９６％Ｔｉ范围内，随钛含量的提高，γ′相析出量增加，进入γ′相中的钛［Ｔｉ（γ′）］从０．９２％增至２．１７％，可见钛在ＧＨ１５０合金中主要起时效强化作用，并显著影响力学性能。随钛含量的增加，合金的室温屈服强度、７００℃拉伸强度和持久强度均提高，同时固溶状态的室温拉伸塑性和持久塑性下降，这是γ′相和μ相综合作用的结果。     

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1060~1120℃温度范围变形时,热加工性能较好。1140℃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.     

Effects of Cobalt on Structure,Microchemistry and Properties of a Wrought Nickel-Base Superalloy

Cobalt in a 17 pct cobalt containing wrought nickel-base superalloy is systematically substituted for by nickel in order to determine the role of cobalt. The eventual goal is to reduce the levels of cobalt, a critical strategic element, in superalloys. It is found that the strengthening γ microstructure is highly heat treatment sensitive. Reducing cobalt did not result in a reduction of the fine γ precipitates after a coarse grain type (blading) heat treatment, but did after a fine grain type (disk) heat treatment. Representative mechanical properties were determined for each case to isolate microstructural and microchemistry effects. Ambient yield strength and tensile strength were seen to decrease by no more than 15 pct and 7 pct, respectively, even when all the cobalt was removed. The decrease in strength is quantitatively discussed and shown to be consistent with the observed microstructural results and microchemistry results obtained using STEM/EDS. Elevated temperature creep and stress rupture resistances were concluded to be affected by alloy cobalt content through its effect on strengthening γ volume fraction. Significant decreases in these properties were observed for the lower cobalt content alloys. Long term aging, precipitate coarsening, and carbide stability results are also presented and discussed.