蒸汽轮机用Waspaloy叶片材料长期时效组织及力学性能

研究了Waspaloy合金在标准热处理状态下,700℃长期时效过程中的组织和力学性能变化。结果表明,长期时效过程中Waspaloy合金析出相主要为MC型碳化物,M23C6型碳化物和γ'相,时效过程中并未发现有害TCP相。M23C6型碳化物在晶界呈链状分布,长期时效过程中其大小、分布基本不变,稳定性良好;γ'相在时效100 h后充分析出,尺寸随时效时间延长而长大,γ'粗化规律符合L-S-W理论,5000 h时效后γ'相形貌仍然为球形。时效100 h合金强度有小幅上升,随后随时效时间延长合金强度变化不大。     

新型高温合金700℃时效组织及力学性能

利用微观组织分析和高温力学性能测试方法，研究了1种新型Ni—Cr—Co基高温合金在700℃长期时效过程中的组织稳定性及其一些力学性能。结果表明：试验合金在700℃时效过程中，析出物有MC，M23C6和γ’；晶内和晶界碳化物MC和M23C6的稳定性好，γ'的粗化为扩散控制的生长过程；在700℃时效初期，室温硬度变化小，随时效时间的增加而减小，这与γ'的粒度、形貌和分布有关；合金的高温拉伸强度和持久强度比Nimonic 263显著提高，且韧塑性好；试验合金在700℃具有稳定的显微组织和较高的高温力学性能。     

热处理对一种镍基高温合金组织和持久性能的影响

研究1220℃×4h固溶+1150℃×4h时效+870℃×24h时效、1220℃×4h固溶+870℃×24h时效和直接进行1100℃×4h三种热处理制度对一种新型镍基高温合金组织和性能的影响.结果表明,这三种热处理制度都能明显提高合金在1100℃/40 MPa的持久寿命,分别将其由24h提高到65、64和53 h.合金的组织铸态由γ、γ'以及少量的MC碳化物和M382硼化物组成.γ'体积约占58％.合金经过固溶+二级时效的处理,MC碳化物主要以颗粒状分布在晶界.同时γ'分为两种尺寸和形态.经过高温固溶+时效热处理后,发生了MC向M23C6退化的反应,使合金的塑性降低.γ'形状为规则的立方体,且尺寸只有0.4 μm.直接1100℃时效也使合金析出两种尺寸和形态的γ',而且使碳化物变得细小.     

长期时效对FGH96粉末高温合金组织稳定性及性能的影响

研究了FGH96粉末高温合金经750℃长期时效1000和3000 h后的晶粒尺寸、晶界形貌、晶粒取向、γ'强化相和碳化物的演变规律及长期时效对合金650℃使用温度下拉伸性能的影响.结果 表明:750℃长期时效对合金的晶粒尺寸、晶界形貌和晶粒取向没有明显影响.然而,长期时效后,合金中γ '相形貌、尺寸和分布发生了显著的变化,大尺寸γ'相先长大后分裂再变小,平均尺寸变大、尺寸梯度降低、间距变大,由双峰分布最终演变为单峰分布;形貌由近球形、方状和蝶状先演变为不规则状,最终又演变回近球状、方状与蝶状.未长期时效合金的晶内和晶界处存在大量富含Ti、Nb元素的块状MC型的碳化物,并与MB型硼化物共存,经750℃长期时效3000 h后没有明显变化.而富含Cr元素的M23C6型小颗粒碳化物经750 ℃长期时效3000 h后,析出量增加并呈链状分布于晶界.长期时效后,FGH96合金650℃拉伸强度降低,塑性提高,主要原因是合金中的γ'相分裂、粗化及晶界处M23C6型碳化物析出呈链状分布所致.     

高温合金服役及修复过程中组织演化规律

研究了ЖC6y合金服役过程中的组织演化规律与恢复热处理后组织形貌的变化.结果表明:经过高温长时服役后合金主要强化相的γ'粒子出现显著退化,γ'粒子的粗化存在Ostwald熟化机制与粒子聚集机制,它的粗化行为可以通过γ'相的形貌特征参数进行表征.MC碳化物在服役中发生分解,转变为周围包覆一层γ'膜的M6C型碳化物.在一定条件下,基体中可直接析出M6C型碳化物.晶界处碳化物有更强烈的分解趋势,晶界处形成包覆一层γ'膜的不连续M6C型碳化物.此种恢复热处理工艺优化了γ'粒子的形貌、尺寸、分布,有效恢复合金的组织退化及显微硬度,形成锯齿晶界,使合金持久性能得到恢复,提高了合金使用寿命.     

LTES700R改进型合金700℃时效组织与性能北大核心CSCD

在LTES700R基础上发展了一种新型镍基耐热合金,并研究了该改进合金700℃时效后的组织与力学性能。结果表明:合金热处理后主要析出相为γ'、TiC、M_(23)C_6;在5000 h时效过程中合金组织结构稳定,Cr_(23)C_6在晶界处不连续分布,γ'粗化不明显;合金硬度随时效时间的延长先增加后缓慢降低。改进合金的室温和高温拉伸强度略低于LTES700R合金,长期时效的冲击韧性大于Nimonic263,晶界处不连续分布的碳化物增加合金晶界结合力,提高改进合金冲击韧性。     

焊接热循环及时效处理对一种Ni-Fe基高温合金的组织和力学性能的影响

采用焊接热模拟实验,研究了焊接热循环对一种700℃超超临界火电机组高温部件候选材料—Ni-Fe基高温合金组织和力学性能的影响.结果表明,固溶态Ni-Fe基高温合金在经过峰值温度为1249℃的焊接热循环后,25和700℃屈服强度和抗拉强度都降低,延伸率升高.对经过焊接热循环后的合金再进行时效处理发现,在25℃时,焊接热循环后再时效样品的屈服强度和抗拉强度与母材时效态相当;在700℃时,焊接热循环后再时效样品的强度高于母材时效态的强度.Ni-Fe基高温合金在高温焊接热循环过程中,强化相γ'以及难溶相MC发生溶解,导致强度下降.经过时效处理后,强化相γ'再次大量析出,同时晶界析出了M23C6.M23C6存在于晶界,并没有造成拉伸性能的弱化.高温焊接热循环使MC发生部分溶解,为M23C6的时效析出提供了C元素.     

LTES700R改进型合金700℃时效组织与性能

在LTES700R基础上发展了一种新型镍基耐热合金,并研究了该改进合金700℃时效后的组织与力学性能。结果表明:合金热处理后主要析出相为γ'、TiC、M_(23)C_6;在5000 h时效过程中合金组织结构稳定,Cr_(23)C_6在晶界处不连续分布,γ'粗化不明显;合金硬度随时效时间的延长先增加后缓慢降低。改进合金的室温和高温拉伸强度略低于LTES700R合金,长期时效的冲击韧性大于Nimonic263,晶界处不连续分布的碳化物增加合金晶界结合力,提高改进合金冲击韧性。     

Ni-Cr-Co基高温合金704℃和760℃时效组织稳定性

利用热力学计算、SEM、TEM和相分析研究了一种新型Ni-Cr-Co基高温合金在704℃和760℃长期时效至2000h后的组织变化。结果表明：该合金标准热处理态和在704℃长期时效后的析出相有MC，M23C6，M6C和γ，在760℃长期时效后还析出了η相。随时效时间增加，γ( η)及碳化物MC，M23C6和M6C的含量变化很小，化学组成稳定，但γ相粗化明显。该合金在760℃时效时，η相的析出随时效时间的增加而加剧，并且呈魏氏体分布。新合金在704℃长期时效时具有良好的组织稳定性，但在760℃时效时组织稳定性较差。     

长期时效对Haynes 282耐热合金组织和力学性能的影响

研究了Haynes 282耐热合金700 ℃下经100、300、1000、3000 h时效处理后组织和力学性能的变化规律。结果表明：282合金主要析出相为M23C6、MC和γ￠相,700 ℃长期时效后,晶界M23C6型碳化物和晶内MC型碳化物发生长大,γ￠相随时效时间的延长长大缓慢。282合金冲击吸收能量随时效时间的延长逐渐下降,晶界链状分布的M23C6型碳化物是造成其冲击吸收能量下降的原因之一。282合金硬度随时效时间的增加而增加,时效过程中γ￠相的含量及尺寸变化对合金硬度影响较大。     

Effects of Hf additions on high-temperature mechanical properties of a directionally solidified NiAl/Cr(Mo) eutectic alloy

In order to improve the high-temperature mechanical properties of NiAl/Cr(Mo) alloys, the effects of Hf additions on microstructure and mechanical properties were systemically examined. Two directionally solidified alloys with composition of Ni-32Al-28Cr-(6−x)Mo-xHf (x = 0.2 and 0.5 at.%, respectively), named as 0.2Hf and 0.5Hf hereafter, were prepared. The Hf additions disturbed the cellular structure. The 0.2Hf alloy consisted of dendritic structure, while the 0.5Hf alloy had an intercellular structure. In the 0.5Hf alloy, the Ni₂AlHf and Ni₁₆Hf₆Si₇ precipitates were also confirmed. The high-temperature strength and brittle-to-ductile transition temperature (BDTT) increased with increasing of Hf additions, due to the different strengthening mechanism. In contrast, the ductility and creep resistance decreased with increasing of Hf because of the disturbance of cellular structure.     

Optimization of mechanical properties of cast NiAl-28Cr-5.5Mo-0.5Hf alloy

The effects of different processing techniques on the microstructure and compressive properties of NiAl-28Cr-5.5Mo-0.5Hf alloys were evaluated. These processing routes can all improve the compressive properties of NiAl-28Cr-5.5Mo-0.5Hf alloys. The microstructural refinement and the stronger precipitation strengthening mechanisms are responsible to the improvement of the compressive properties under the condition of higher undercooling degree. In addition, high magnetic field treatment and trace rare earth elements addition can significantly optimize the mechanical properties of NiAl-28Cr-5.5Mo-0.5Hf alloy. The improvement of NiAl-28Cr-5.5Mo-0.5Hf alloy seems to be realized by a complicated combination of different processing route. A directional solidification at a high drawing rate under high magnetic field for NiAl-28Cr-5.5Mo-0.5Hf alloy containing minor rare earth element is a desirable route to the high performance NiAl-28Cr-5.5Mo-0.5Hf alloy.     

Microstructure and Mechanical Properties Determined in Compressive Tests of Quasi-Rapidly Solidified NiAl-Cr(Mo)-Hf Eutectic Alloy After Hot Isostatic Pressure and High Temperature Treatments

The effect of high cooling rate of approximately 10² K/s and subsequent hot isostatic pressure (HIP) and high temperature (HT) treatment on the microstructure and mechanical properties of NiAl-based intermetallic alloys was investigated. The results reveal that rapid solidification refines the microstructure of the NiAl-Cr(Mo)-0.5Hf eutectic alloy and transforms the Ni₂AlHf Heusler phase, which is present in the equilibrium state to a metastable Hf(Ni, Al, Cr) solid solution phase. Simultaneously, the shape and distribution of the Hf(Ni, Al, Cr) solid solution phase were considerably improved. After the HIP treatment, the Hf(Ni, Al, Cr) solid solution phase has changed from continuous distribution along eutectic cell boundaries into semicontinuous distribution, and the primary NiAl(Cr, Mo) phase has coarsened. The HT treatment reduces the volume fraction of the primary NiAl(Cr, Mo) phase and optimizes the distribution of the Hf(Ni, Al, Cr) solid solution phase. Rapid solidification and the resulting fine-grained microstructure will significantly improve the mechanical properties of the alloy in compression tests. However, additional HIP and HT treatments enhance the high-temperature strength properties obviously.     

Hf含量对DD6单晶高温合金组织和持久性能的影响

研究了Hf含量对DD6单晶高温合金热处理组织和持久性能的影响。结果表明,在本实验研究范围内,随着Hf含量的增加,热处理后合金残余共晶量增加,枝晶干的γ′相尺度无明显变化,枝晶间的γ′相尺度有所减小。在1100 ℃, 140 MPa条件下,随着Hf含量的增加,合金的持久寿命先升高后降低, 持久延伸率先快速增加, 然后慢速增加。讨论了不同Hf含量合金的显微组织与持久性能的关系     

Microstructure and room temperature mechanical properties of NiAl–Cr(Mo)–(Hf,Dy) hypoeutectic alloy prepared by injection casting

The NiAl–Cr(Mo)–(Hf,Dy) hypoeutectic alloys were prepared by conventional casting and injection casting techniques respectively, and their microstructure and room temperature mechanical properties were investigated. The results reveal that with the addition of Hf and Dy, the Ni₂AlHf Heusler phase and Ni₅Dy phase form along the NiAl/Cr(Mo) phase boundaries in intercellular region. By the injection casting method, some Ni₂AlHf Heusler phase and Ni₅Dy phase transform into Hf and Dy solid solutions, respectively. Moreover, the microstructure of the alloy gets good optimization, which can be characterized by the fine interlamellar spacing, high proportion of eutectic cell area and homogeneously distributed fine Ni₂AlHf, Ni₅Dy, Hf solid solution and Dy solid solutions. Compared with conventional-cast alloy, the room temperature mechanical properties of injection-cast alloy are improved obviously.     

Effects of incorporation of Si or Hf on the microstructure and mechanical properties of Ti-Al-N films prepared by arc ion plating (AIP)

Ti-Al-N, Ti-Al-Si-N and Ti-Al-Hf-N films were deposited on 1Cr11Ni2W2MoV stainless steel by arc ion plating (AIP) with a Ti₇₀Al₃₀, a Ti₆₀Al₃₀Si₁₀ and a Ti₆₈Al₃₀Hf₂ cathode, respectively. The effects of Si or Hf addition on the composition, microstructure and mechanical properties of the Ti-Al-N films were investigated by EPMA, TEM, SEM, XRD, micro-hardness and wear tests. The results show that all the deposited films possessed B1 structure. With the incorporation of Si or Hf, the texture of Ti-Al-N films remarkably changed from preferred orientation of (220) to mixture broadened orientations of (111), (200) and (220), the mean crystallite size of Ti-Al-N decreased from ~ 90 nm to ~ 30 and ~ 15 nm and no peaks of crystalline Si₃N₄ were detected from XRD analyses. Due to the addition of Si or Hf, the micro-hardness of Ti-Al-N films increased remarkably from 23.5 Gpa to 33.6 or 29.5 GPa, and the wear resistance was also enhanced. The effects of incorporation of Si or Hf on the microstructure and mechanical properties of Ti-Al-N films are discussed.     

铂族金属高温固溶强化型合金

讨论了高温固溶强化机制和合金元素对Pt固溶强化效应.介绍了铂族金属和Pt-Rh、Pt-Ir和Pt-Pd-Rh固溶型合金的的高温力学性能.借助不同的强化机制,在Pt-Rh或Pt-Pd-Rh合金中添加少量Ir、Ru、Mo、Au等组元,或微量稀有金属Zr、Hf或稀土金属,可以提高合金的高温强度性质和改善抗蠕变能力.     

Microstructure and mechanical properties of HfC reinforced W matrix composites regulated by trace Zr

In this study, the W-HfC-Zr composites with various Zr content were fabricated via plasma activated sintering. The relative density, microstructure, microhardness, as well as mechanical properties of these composites were investigated. The W-HfC-Zr composite with 1.0 wt% Zr content had high relative density of 97.56%, exhibited the higher microhardness of 614 Hv, compressive yield strength of 1.85 GPa and bending strength of 880 MPa, which attributing to Zr captured impurity oxygen and generated solid-solution oxide (Hf, Zr)O. The enhancement mechanisms of trace Zr addition on microstructure and mechanical properties were proposed.     

热处理对Hf-基非晶合金力学性能的影响

采用铜模浇铸法制备Hf44.5Cu27Ni13.5Ti5Al10块体非晶合金,并对其进行等温退火处理。利用X射线衍射仪（XRD）和透射电镜（TEM）对非晶合金的晶化行为进行了分析,并通过MTS810实验机及场发射扫描电子显微镜（FESEM）研究了等温退火对合金力学性能的影响。结果表明,该非晶合金等温退火相转变进程为：非晶→非晶＋Al16 Hf6Ni7→非晶＋Al16 Hf6Ni7＋CuTi2→CuHf2＋CuTi2。合金断裂强度随退火温度的升高先增大后减小。743 K等温退火后,合金断裂强度达到最大值2400 MPa,弹性应变为3.0%。在Hf44.5Cu27Ni13.5Ti5Al10块体非晶合金压缩断口上观察到纳米级韧窝及周期性条纹结构。随着退火温度的升高,周期性条纹间距逐渐减小直至消失,断口形貌呈现为脆性解理断裂的河流状花样。     

Synthesis,properties and XPS analysis of Cu-,Ni-,Ti-based metallic glasses

Metallic glasses（MG）represent an interesting group of materials as they possess outstanding physical,chemical and mechanical properties compared to their crystalline counterparts.This paper reviews the synergistic influence of Ni and Nb elements on thermal stability of supercooled liquid and corrosion resistance of as-cast Cu-Zr（Hf）-Ti-Ni-Nb bulk metallic glasses（BMGs）.Additionally,in-situ second phase reinforced Cu-based BMG composites with high corrosion resistance and excellent mechanical properties are investigated.On the other hand,this paper reports the development of ultra-high corrosion resistant Ni-based metallic glasses at high temperatures for their potential applications.Corrosion resistance and XPS analysis of the Nifree Ti-based BMG are also introduced.