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直流电场对一种镍基单晶高温合金力学性能的影响 总被引:1,自引:0,他引:1
采用电场凝固技术在自制电场定向凝固装置上进行电场单晶生长,研究了直流电场对一种镍基单晶高温合金室温拉伸性能和高温持久性能的影响.结果表明,随着电流密度增大,合金的室温屈服强度明显提高,但抗拉强度无明显改善,且塑性降低;在980℃和221MPa条件下,高温持久时间显著延长,持久塑性得到改善.利用扫描电镜和电子探针对该合金的凝固组织、合金成分分布和断口形貌进行了分析.结果表明,直流电场引起枝晶间距及γ′相尺寸减小、成分偏析减轻,共晶和亚晶界减少.直流电场作用导致的γ′相尺寸减小及成分偏析减轻导致的γ/γ′错配度变化,对合金的屈服强度和高温持久性能的提高有贡献. 相似文献
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镍基单晶合金CMSX-2高温蠕变后的显微组织及合金元素分布特征 总被引:5,自引:0,他引:5
对单晶合金CMSX-2在1000℃下分别进行了载荷为95,120,165和216MPa的拉伸蠕变实验,在SEM下观察了合金试样枝晶干的枝晶间区域中γ′相的形态,有EDS方法分析了上述枝晶区域中合金元素的分布特点,对枝晶干和枝晶间区域中γ′形成元素Al,Ti,Ta的原子分数与基体固溶元素Cr,Co,W的原子分数的比值(CA1+CTi CTa)/(Ccr CCo Cw)和同一元素在枝晶与在枝晶干中的原子分数比(Ci/Cc)Ta,Cr,Co,W以及共格错配度的变化对γ′相粗化程度和筏形化形态的影响分别进行了讨论。 相似文献
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利用四轴X射线衍射仪(XRD)测定片状DD10镍基单晶高温合金减薄至不同厚度时基体相(γ)和沉淀强化相(γ′)的晶格常数.根据减薄过程中两相间约束变化得到晶格常数和错配度变化规律,计算出合金从三维块体错配应力状态向二维平面应力状态转化达到失稳状态的临界厚度以及与不同应力状态对应的晶格错配度.依照一定的假设条件,推算出与应力松弛条件对应的无错配应力状态下两相的晶格常数.分析结果表明:合金减薄达到临界厚度后,γ′相晶格常数随厚度减小而线性变小,γ相晶格常数无明显变化,与此对应的晶格错配度绝对值变大;减薄过程伴随γ/γ′两相间约束的减弱和相间微观应力松弛,晶格取向差和晶体嵌镶度增大,表层应力状态向平面应力状态转化.测量得到的临界厚度与无错配应力状态下的晶格常数可为高温合金单晶材料的应用设计和残余应力测试提供参考. 相似文献
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镍基单晶合金枝晶型区域相成分最优化测算法 总被引:1,自引:0,他引:1
建立了用测算镍基单晶高温合金枝晶典型区域相成分的最优化数学模型,根据电子探针对枝晶典型区域成分的测定结果,运用BFGS拟Newton法及CONSTR约束优化算法,可以计算枝晶各典型区域中γ和γ′相成分,以镍基单晶合金CMSX-2和CMSX-4为对象,对优化测算结果进行了分析,证实了该方法的可行性。 相似文献
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Ru和Cr对镍基单晶高温合金γ/γ′热处理组织演变的影响 总被引:1,自引:0,他引:1
通过对6种不同Ru(0—5.1%,质量分数,下同)和Cr(0—5.7%)含量的镍基单晶高温合金1100℃的时效和热处理组织观察与γ/γ′两相的成分分析,研究了Ru和Cr的独立和交互作用对合金元素成分分配比及热处理组织演变的影响.经1100℃/8 h时效后,在枝晶干处,不含Ru和Cr的基础合金γ′相接近球形,Re在该合金γ/γ′两相中的成分分配比较低,错配度接近于0.在基础合金中加入高Ru后,γ′相立方度和Re的成分分配比略有增大,错配度变负;在不含Ru合金与含Ru合金中,随着Cr含量的增大,γ′相的立方度和Re的成分分配比均显著增大,错配度明显变负.1100℃非加载下的长期热处理研究表明:γ′相接近球形且错配度接近于0的合金γ′相形貌稳定,在2000 h内只出现了粗化,没有发生筏排化现象;γ′相呈中间态并且错配度较小的合金γ′相粗化趋势较为明显;γ′相接近立方体形且错配度中等的合金在热处理800 h后形成近似筏排组织;同时加入Ru和Cr,随着Re的成分分配比和错配度的增大,γ′相为立方体形或长方体形的合金筏排化时间提前;其中高Ru中Cr合金热处理200 h就出现筏排化趋势,而错配度最高的高Ru高Cr合金热处理... 相似文献
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镍基单晶高温合金CMSX—2原始树枝状晶中γ相的定向粗化 总被引:3,自引:0,他引:3
在760-1050℃和750-140MPa范围内,选择不同温度和应力的配合对CMSX-2合金进行持久拉伸至断裂,观察了试件原始树枝状晶区域(枝晶干、枝晶屑及枝晶间)中γ相的定向粗化及合金元素的分布特征。结果表明,γ的定相经程度在枝晶干内最大,在枝晶内次之,在枝晶间最小,在所有这些区域中,试验温度较高者的暄向粗化程度较大;各试件在持久试验后,γ形成元素W,Cr和Co,γ形成元素A1和Ta,在原始支状 相似文献
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研究了3种不同含Ti量单晶高温合金的铸态、热处理态组织及持久性能。结果表明:Ti含量对合金的微观组织和持久性能都有明显的影响。随着钛含量的增加,铸态合金枝晶间区域的共晶尺寸和含量明显增大、增多,枝晶间区域的面积也逐渐增大。热处理后,3种合金的枝晶干处的γ′相形态基本一致,都为规则的立方体γ′相,尺寸大约为400nm-500nm。随着钛含量的增加,合金的持久寿命略有降低,延伸率略有增加。 相似文献
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Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang 《金属学报(英文版)》2019,32(6):684-694
In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone. 相似文献
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After nearly two years'tense construction the first phase of industrialized base of Shenyang Research Institute of Foundry 《中国铸造》2008,5(1):63-64
After nearly two years' tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry (SRIF), located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation. 相似文献
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Z. Sun S.L. Zheng Y. Zhang 《金属学报(英文版)》2007,20(3):187-192
Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process. 相似文献
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R. González-Martínez 《金属学报(英文版)》2007,20(4):235-240
The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke. 相似文献
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The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C). 相似文献
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The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel. 相似文献
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This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
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Chao Yang He-Fei Huang Massey de los Reyes Long Yan Xing-Tai Zhou Tian Xia De-Liang Zhang 《金属学报(英文版)》2015,28(7):809
Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties. 相似文献
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Lei Li Bo Xu Wei-Ping Tong Hui Zhang Chun-Yan Ban Li-Zi He Zhi-Hao Zhao Yu-Bo Zuo Qing-Feng Zhu Jian-Zhong Cui 《金属学报(英文版)》2015,28(6):725
A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed. 相似文献
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综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。 相似文献