一种镍基单晶高温合金高温持久性能的各向异性

测定了一种镍基单晶高温合金[001],[011]和[111]三个取向的高温持久性能。结果表明,[001]方向塑性最好,[111]方向寿命最长,而[011]方向各性能指标都较低,组织分析显示,[111]取向启动多个滑移系,形成界面位错网,且分切应力低,因而寿命长;[001]取向等价滑移系最多,可有效钝化微裂纹,因而塑性最好;而[011]取向切应力高,滑移系少,形变孪晶易促进裂纹萌生,所以寿命短且塑性也低,三种试样在持久过程中都形成一种沿枝晶方向的藤状γ′,是由各枝晶间的微小取向差引起的,这些滕状γ′可以成为一种重要的裂纹源。     

固溶处理对1种镍基单晶高温合金组织的影响

采用光镜、扫描电镜对1种镍基单晶高温合金的铸态组织和不同温度固溶处理后的组织进行了观察，研究了不同温度固溶处理对γ′相尺寸、γ／γ′共晶、成分偏析的影响。结果表明：合金枝晶间γ′相的固溶温度高于枝晶干γ′相的固溶温度，随固溶处理温度的升高，γ′相尺寸略有增加，γ／γ′共晶量及成分偏析降低；1290℃，4h，AC固溶处理后合金枝晶干、间γ′相全部固溶，1310℃，4h，AC固溶处理后合金中γ/γ′共晶全部消除，1320℃固溶处理时，合金中出现初溶现象；确定1310℃，4h，AC为合金的固溶处理工艺。     

钴、钨和钛对镍基单晶高温合金持久性能的影响

采用正交实验设计方法，探讨了Co，W和Ti及其含量对镍基单晶高温合金持久性能的影响，通过数学分析，对合金成分进行了优化。结果表明：此合金系中Ti含量对持久寿命影响最大，Co次之，W对持久寿命影响最小；当Co，W和Ti含量（ω，％）分别为10，8和0时合金具有较好的持久性能。此合金长期时效后还显示出良好的组织稳定性。     

熔体过热处理对DD98镍基单晶高温合金持久性能的影响

研究了在不同熔体过热处理条件下一种镍基单晶高温合金的高温持久性能,并观察了持久断裂后的断口及变形组织。结果表明:随着熔体处理温度的提高和保温时间的加长,γ’筏型组织的完善程度增加,厚度减小;断口上韧窝数量、尺寸、形状均不同,显示出韧性断裂特征;热处理态单晶高温合金在1010℃,248 MPa下的高温持久寿命有大幅度提高、高温伸长率增加38.9%。     

两种热处理对镍基单晶高温合金CMSX-4微观组织和持久性能的影响

研究了第2代镍基单晶高温合金CMSX-4的标准多级预处理+固溶热处理(多级固溶)和一种超初熔点固溶热处理工艺对其组织、元素偏析和持久性能的影响。结果表明:合金经1280℃/1 h+1290℃/2 h+1300℃/6 h,AC+1140℃/4h,AC+870℃/16 h,AC多级固溶热处理(工艺1)后,元素偏析得到较明显改善,在980℃/250 MPa和1070℃/140 MPa条件下的持久寿命分别为207.50 h和280.84 h。工艺1的固溶热处理过程中形成较多固溶微孔,铸态微孔尺寸增大,这些显微孔洞在持久实验中成为合金的裂纹源,使合金发生微孔聚集型断裂,是CMSX-4合金发生持久断裂的关键原因。合金经1320℃/3 h,AC+1140℃/4 h,AC+870℃/16 h,AC超初熔点热处理(工艺2)后,改善合金元素偏析情况不如工艺1,但采用的固溶处理制度形成的微孔数量较少,持久寿命更高,在980℃/250 MPa和1070℃/140 MPa条件下的持久寿命分别为293.08 h和310.10 h。     

熔体过热处理对M963合金组织和高温持久性能的影响

对M963合金熔体进行了过热处理并在1248K／225 MPa条件下测试了其持久性。结果表明，随熔体过热温度的升高，铸态组织中的初生MC碳化物不断细化和均匀分布，合金的持久断裂寿命和塑性明显提高，但温度高达2023K的熔体过热处理，使合金中的气体含量升高，导致显微疏松增加，持久性能降低。在1923K温度下进行熔体过热处理，可使M963合金在1248K／225MPa条件下的持久寿命和持久塑性同时提高一倍以上。     

固溶热处理对新型镍基粉末FGH98Ⅰ高温合金组织与性能的影响

对新型镍基粉末高温合金(FGH98Ⅰ)在不同温度下进行固溶热处理,采用热力学相计算、光学显微镜、场发射扫描电镜及化学相分析等研究了亚固溶和过固溶合金的析出相和显微组织,并综合分析了组织与性能的关系。结果表明:FGH98Ⅰ合金经1130℃亚固溶和1190℃过固溶处理后的析出相均为γ’、MC、M23C6和M3B2等,未发现TCP(拓扑密堆)相。FGH98Ⅰ合金亚固溶热处理后晶粒稍有长大,存在尺寸不同的初次、二次和三次γ′相;过固溶热处理合金的晶粒明显长大,存在单模分布的二次γ′相;前者由于晶粒较小使强度更高,后者因减小二次γ′相尺寸和消除初次γ′相,PPB(原始颗粒边界)和残余枝晶,提高了合金的高温塑性和持久性能,说明不同晶粒尺寸和γ′相特征是FGH98Ⅰ盘件获得双性能的关键因素。     

Al含量对镍基单晶合金组织及持久性能的影响

研究了铝含量对一种镍基单晶合金铸态和热处理态显微组织的影响,测试了单晶合金的高温持久性能,利用金相显微镜、SEM、TEM、XRD等考察了持久断裂试样的微观形貌.结果表明,单晶合金的铸态组织由粗大的γ'、细小的γ'和γ组成,随Al含量的增加,粗大的γ'相数量增多、尺寸增大.固溶处理不能使粗大的γ'完全固溶,持久断裂裂纹主要在粗大的γ'/γ界面产生,并沿γ'/γ界面扩展,严重损伤合金的高温持久性能.     

Al、Ti和Ta含量对镍基单晶高温合金时效组织的影响

研究了几种不同含量γ′相形成和强化元素(Al、Ti和Ta)的单晶高温合金在热处理以及长期时效处理后的组织演化.结果表明:在经过相同的热处理后,随着Al、Ti和Ta总含量的增加,γ′相的尺寸逐渐增大,γ′相形貌由圆形向立方形再向不规性形状转变.在950 ℃的长期时效处理过程中,γ′相的尺寸明显增大,立方度降低,直到1000 h,γ′相也没有发生连接和形筏.1050 ℃、500 h后,γ′相形貌尺寸明显增大、立方度降低.合金A和E仍保持原来形状,合金B、C和D的γ′相发生连接和形筏.在2种时效条件下,合金E中均有TCP相(μ相)析出.     

热处理工艺对镍基单晶合金性能的影响

通过能谱分析和拉伸蠕变试验研究了热处理工艺对1.8Re-4.0W镍基单晶合金性能的影响.试验结果表明,合金的最佳固溶处理温度为1320℃;合金经1280℃×4h空冷均匀化处理,1320C×4h空冷固溶处理,再1080℃×4h空冷时效和870℃×8h3次时效后,在1072℃、137 MPa条件下的蠕变寿命达221 h.该...     

Ru对镍基单晶高温合金高温持久性能的影响(英文)

在真空定向炉中浇注了具有[001]方向的不含Ru和含Ru两个单晶高温合金,其它合金元素的含量基本相同,研究Ru对单晶高温合金在(980℃,250 MPa),(1100℃,140 MPa)和(1120℃,140 MPa)条件下持久性能的影响。结果表明,加入Ru能提高单晶高温合金的高温持久性能,提高作用随着温度的升高而降低。在断裂后的两种合金试样中都观察到γ′相定向粗化和筏排化,并且在(1100℃,140 MPa)和(1120℃,140 MPa)条件试样中有针状的TCP相析出,而在(980 ℃,250 MPa)条件试样中无TCP相析出。加入Ru减少了TCP相的析出数量。最后,讨论了加入Ru带来的合金组织变化进而提高合金持久性能的原因。     

Temperature dependence of deformation mechanism in single crystal Ni-base superalloy

The tensile behavior of a new single crystal Ni-base superalloy was studied at various temperatures.Specimens were strained to fracture in the temperature range from 20 ℃ to 1 000 ℃. σ0.2 is essentially unaffected by temperatures between 20 ℃ and 400 ℃. At higher temperatures it increases until it reaches a maximum at about 800 ℃. Beyond 800 ℃ a sharp decrease of strength is observed. There is a slight fluctuation in ductility between 20 ℃ and 800 ℃. The elongation to fracture increases from 10% to 36% as the temperature increases from 800 ℃ to 1 000 ℃. The deformation is dominated by γ' shearing and the high-density dislocations are observed in matrix channels at low temperatures. The dislocation microstructure is inhomogeneous due to the formation of dislocation concentrations with high-density tangling at intermediate temperatures. The networks deposited at the γ'/γ'interfaces prevent dislocations from entering the γ' precipitates at high temperatures.     

真空热处理后Ni-Co-W-Ta-Al-Cr-Mo-Re-Nb-Hf系镍基单晶高温合金表面的氧化状态分析

将Ni-Co-W-Ta-Al-Cr-Mo-Re-Nb-Hf系镍基单晶高温合金试样在真空炉中完成固溶和时效真空热处理,由于设备状态或是其他原因造成试样表面存在不同程度的氧化(即表现出不同的氧化色),利用光学显微镜、扫描电镜和能谱分析对不同氧化色的单晶高温合金试样表面氧化微观组织和氧化物成分进行观察和测试。结果表明:单晶高温合金试样随着氧化程度的加深表面氧化物的组织状态和成分存在不同程度的变化,对于该氧化问题应详细分析原因并对症处理,最终才能获得表面质量满足要求的单晶高温合金制件。     

Effect of carbon on microstructure and mechanical properties of DD99 single crystal superalloy

The effects of carbon on the microstructure and mechanical properties of DD99 single crystal superalloy were investigated. The results show that stress rupture life of DD99 alloy possesses peak value at carbon content of 0.03%（mass fraction）. As carbon addition is greater than 0.03%, the stress-rupture life decreases with the increase of carbon content. The tensile strength and yield strength of DD99 alloy reach peak value at 0.08% carbon and 760 ℃. On the contrary, the tensile strength and yield strength have minimal values at 0.08% carbon and 900℃. The tensile ductility of DD99 alloy basically decreases with the increase of carbon content at 760 ℃ or 900 ℃. The amount of carbides greatly increases with the addition of carbon content. Dislocation moving is retarded by carbides so that dislocation networks are apt to form, which has an important role on the mechanical properties in DD99 single crystal superalloy.     

热处理过程中DD6单晶高温合金的组织演化规律与力学性能

研究了DD6单晶高温合金在热处理过程中的显微组织演化规律以及初熔组织的生成机理。通过研究不同固溶时效处理对γ′相形貌、尺寸分布和体积分数的影响且分析了完全热处理后合金的显微硬度和拉伸性能,从而确定了合金最佳的热处理工艺。结果表明,通过差热分析法和金相观察法确定合金的初熔温度在1300~1310 ℃。在1315 ℃固溶处理4 h,枝晶间/枝晶干γ′相尺寸趋于一致,呈立方状均匀排列。在固溶处理过程中,γ/γ′共晶组织熔化生成了不规则初熔组织。在不同的一次时效工艺下,1120 ℃时效4 h空冷后,γ′相立方度更好,尺寸分布更均匀。合金最佳的热处理工艺为1290 ℃×1 h+1300 ℃×2 h+1315 ℃×4 h, AC+1120 ℃×4 h, AC+870 ℃×32 h, AC。合金在完全热处理后,随拉伸温度从室温升高至850 ℃时,强度达到峰值,温度继续升高,强度下降;在760 ℃拉伸时塑性最差,随着拉伸温度从760 ℃升高到950 ℃,塑性提高。     

Effect of anisotropy on microstructure and high temperature stress rupture properties of Ni3A1 base single crystal alloy

The effect of anisotropy on microstructure and high temperature stress rupture property of Ni3A1 base single crystal alloy was investigated. The single crystal specimens were produced by screw selection crystal method. The microstructures were examined by OM, SEM, TEM and X-ray EDS techniques. The stress rupture tests were can-led out in air by constant load creep machines under 1 100 ℃ and 130 MPa. The experimental results show that the dendrites preferential orientation deviates certain angles to heat flow orientation, and the secondary arms occur for different crystallographic orientations. The single crystal alloy with different orientations shows obvious anisotropy during tensile stress rupture tests under 1 100 ℃ and 130 MPa. The 〈111〉 orientation specimen has the best stress rupture life of 211 h. The high ductility at 1 100 ℃ of the 〈001〉 orientation specimen may be attributed to the most multiple equivalent slip systems.     

The microstructure of a single crystal superalloy after different aging heat treatments

To study the influence of aging heat treatments on the microstructure of single crystal superalloys with high content of refractory elements and optimal the aging heat treatment regimes, a single crystal superalloy containing 22 wt% refractory elements was investigated.Results show that for the experimental alloy, even the homogenization-solution heat treatment for 25 h cannot homogenize the alloying elements completely. During primary aging heat treatment, γ' phase grows larger and turns to regular cubes. Higher aging temperature induces larger γ' cubes. For specimens with primary aging heat treated at 1120 ℃,γ' morphology does not change apparently during secondary aging heat treatment. For specimens with primary aging heat treatment at 1150 ℃,γ'phase in interdendrite grows obviously comparing with that in dendrites. By analyzing the precipitating kinetics of γ'phase, it is found that owning to the dendrite segregation and different aging heat treatment temperatures, γ' phase at different regions grows under the control of different factors at different aging heat treatment stages. The two controlling factors that are driving forces of phase transformation and element diffusion rate induce obviously different growth rates of γ' phase. As a result, the γ'-precipitating behaviors are variable based on different solute concentrations and aging temperatures. For advanced single crystal superalloys that are supposed to be used at relatively high temperatures, the final γ' size after aging heat treatment is suggested to be close to the crossing point of diffusion controlling curve and driving force controlling curve corresponding to the serving temperature. And then,high-temperature properties can be improved.