Microstructural Stability and Creep Performance of a Novel Low-Cost Single Crystal Superalloy

Z. H. Tan,X. G. Wang,Y. L. Du,Y. M. Li,Y. H. Yang,J. L. Liu,J. D. Liu,J. G. Li,Y. Z. Zhou,X. F. Sun 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The increasing pursuit of advanced aero-engines with lower ratio between the cost and performance has greatly promotedthe demanding of single crystal superalloys characterized by low cost and outstanding temperature capability. In this study,a novel low-cost single crystal superalloy was designed and the creep tests as well as micro-characterization were carried outon the experimental alloy. The results illustrated that the novel single crystal alloy exhibited an ideal microstructural stabilitywithout precipitating TCP phases, after long-term thermal exposure at the ultimate service temperature of third generationsingle crystal superalloys. Moreover, the experimental alloy with only 3 wt% Re addition demonstrated remarkable creepresistance and maintained a very low minimum creep rate at 1100 °C/137 MPa and 1120 °C/137 MPa, while the accumulationand coalescence of micro-pores had eventually led to the alloy fracture. Apart from that, the compact interfacial dislocationnetworks the 2nd γ′ phase were observed after high-temperature creep rupture, and the typical a < 010 > superdislocationswith relatively poor mobility was found at 1120 °C. At 760 °C/800 MPa, both the minimum creep velocity and entire creepstain was increased evidently, however, the ultimate creep rupture life of the alloy had still reached 200 h. The correspondingdeformation mechanism was identified as the combination of superdislocation pairs shearing and a/3 < 121 > partial dislocationcutting the γ′ phase with a SISF being generated. In general, the novel single crystal alloy characterized by remarkablemechanical properties and cost reduction possesses a great potential for future application in the advanced aircraft engines.

REAL-TIME PERSONAL DOSE MEASUREMENT AND MANAGEMENT SYSTEM RESEARCH IN CHINA

Z.Y. Zhang,C.Cheng,Z.S. Liu,H.T. Yang,C.M. Deng,X. Zhang,Z.J. Guo 대한방사선방어학회 2001 방사선방어학회지 Vol.26 No.3

Comparison of Gene Expression Patterns in Longissimus dorsi of Pigs between the High-parent Heterosis Cross Combination andrace×Large White and the Mid-parent Heterosis Cross Combination Large White×Meishan

Liu, G.Y.,Xiong, Y.Z.,Deng, C.Y.,Zuo, B.,Zhang, J.H. Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.9

In order to detect the molecular mechanism of heterosis in pigs, the mRNA differential display technique was performed to investigate the differences in gene expression of pig's Longissimus dorsi between the high-parent heterosis cross combination Landrace${\times}$Large White and the mid-parent heterosis cross combination Large White${\times}$Meishan. Three pig purebreds, Large White, Meishan, and Landrace and four types of reciprocal $F_1$ hybrids were analyzed using nine 3'-end anchored primers in combination with ten 5'-end arbitrary primers and nearly 7,000 reproducible bands were examined. The patterns of gene expression of each cross combination were analyzed and eight common patterns (fifteen kinds) were found. When the results from the two cross combinations were put together and compared, eight different typical expression patterns were observed, these indicated that the patterns of gene expression of these two cross combinations had obvious differences. Gene expression correlation and cluster analyses of the two cross combinations indicated that the gene expression of the mid-parent heterosis cross combination was correlated with maternal effect, but in the high-parent heterosis cross combination, paternal effect acted in the gene expression of the hybrids or the gene expression of the hybrids was biased towards one parent.

SOME FIXED POINTS FOR EXPANSIVE MAPPINGS AND FAMILIES OF MAPPINGS

Liu, Z.,Feng, C.,Kang, S.M.,Kim, Y.S. The Youngnam Mathematical Society Korea 2002 East Asian mathematical journal Vol.18 No.1

In this paper we obtain some fixed points theorems of expansive mappings and several necessary and sufficient conditions for the existence of common fixed points of families of self-mappings in metric spaces. Our results generalize and improve the main results of Fisher [1]-[5], Furi-Vignoli [6], $Is\'{e}ki$ [7], Jungck [8], [9], Kashara-Rhoades [10], Liu [13], [14] and Sharma and Strivastava [16].

Improving solution-processed n-type organic field-effect transistors by transfer-printed metal/semiconductor and semiconductor/semiconductor heterojunctions

Liu, C.,Xu, Y.,Liu, Z.,Tsao, H.N.,Mullen, K.,Minari, T.,Noh, Y.Y.,Sirringhaus, H. Elsevier Science 2014 Organic Electronics Vol.15 No.8

Solution-processed n-type organic field effect transistors (OFETs) are in need of proper metal contact for improving injection and mobility, as well as balanced hole mobility for building logic circuit units. We address the two distinct problems by a simple technique of transfer-printing. Transfer-printed Au contacts on a terrylene-based semiconductor (TDI) significantly reduced the inverse subthreshold slope by 5.6V/dec and enhanced the linear mobility by over 5 times compared to evaporated Au contacts. Hence, devices with a high-work-function metal (Au) are comparable with those with low-work-function metals (Al and Ca), indicating a fundamental advantage of transfer-printed electrodes in electron injection. We also transfer-printed a poly(3-hexylthiophene) (P3HT) layer onto TDI to construct a double-channel ambipolar transistor by a solution process for the first time. The transistor exhibits balanced hole and electron mobility (3.0x10<SUP>-3</SUP> and 2.8x10<SUP>-3</SUP>cm<SUP>2</SUP>V<SUP>-1</SUP>s<SUP>-1</SUP>) even in a coplanar structure with symmetric Au electrodes. The technique is especially useful for reaching intrinsic mobility of new materials, and enables significant enlargement of the material tanks for solution-processed functional heterojunction OFETs.

EFFECTS OF ALTITUDE ON COMBUSTION CHARACTERISTIC DURING COLD START OF HEAVY-DUTY DIESEL ENGINE

Z. C. KAN,D. M. LOU,Z. Z. CAO,Z. Y. HU,S. LIU,Z. H. YANG 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.2

Altitude has a significant effect on combustion of heavy-duty diesel engines, especially during cold start. An experimental study on a heavy-duty diesel engine operating at different altitudes was conducted. Tests were based on a direct injection (DI) turbocharged diesel engine with intake and exhaust pressure controlled by the plateau simulation test system to stimulate altitude conditions including 0 m, 1000 m, 2000 m, 3000 m and 4000 m. Results indicated that the compression and expansion resistance moment reduced and the speed increased during the cranking period. The peak pressure of several cycles was increased during the start-up period; however, the expansion pressure dropped more and the indicated mean effective pressure (IMEP) reduced as the altitude rose. While at an altitude of over 2000 m, the peak pressure fluctuated obviously during the start-up period. The higher the altitude was, the more the fluctuation amplitude and cycle number increased and combustion instability enhanced, which resulted the start-up period time increasing at high altitude. When the altitude rose, the cycle-to-cycle variation of the peak pressure and speed fluctuation increased during the idle, the ignition and CA50 were delayed and the combustion duration was shortened. The effect of altitude on combustion characteristics of the diesel engine was more significant during the start-up period than during its idle period.

Unsteady separated and reattaching turbulent flow over a two-dimensional square rib

Liu, Y.Z.,Ke, F.,Sung, H.J. Academic Press 2008 Journal of fluids and structures Vol.24 No.3

The spatio-temporal characteristics of the separated and reattaching turbulent flow over a two-dimensional square rib were studied experimentally. Synchronized measurements of wall-pressure fluctuations and velocity fluctuations were made using a microphone array and a split-fiber film, respectively. Profiles of time-averaged streamwise velocity and wall-pressure fluctuations showed that the shear layer separated from the leading edge of the rib sweeps past the rib and directly reattaches on the bottom wall (x/H=9.75) downstream of the rib. A thin region of reverse flow was formed above the rib. The shedding large-scale vortical structures (fH/U<SUB>0</SUB>=0.03) and the flapping separation bubble (fH/U<SUB>0</SUB>=0.0075) could be discerned in the wall-pressure spectra. A multi-resolution analysis based on the maximum overlap discrete wavelet transform (MODWT) was performed to extract the intermittent events associated with the shedding large-scale vortical structures and the flapping separation bubble. The convective dynamics of the large-scale vortical structures were analyzed in terms of the autocorrelation of the continuous wavelet-transformed wall pressure, cross-correlation of the wall-pressure fluctuations, and the cross-correlation between the wall pressure at the time-averaged reattachment point and the streamwise velocity field. The convection speeds of the large-scale vortical structures before and after the reattachment point were U<SUB>c</SUB>=0.35U<SUB>0</SUB> and 0.45U<SUB>0</SUB>, respectively. The flapping motion of the separation bubble was analyzed in terms of the conditionally averaged reverse-flow intermittency near the wall region. The instantaneous reattachment point in response to the flapping motion was obtained; these findings established that the reattachment zone was a 1.2H-long region centered at x/H=9.75. The reverse-flow intermittency in one period of the flapping motion demonstrated that the thin reverse flow above the rib is influenced by the flapping motion of the separation bubble behind the rib.

Unambiguous Evidence for Existence of Antiferromagnetic Interlayer Coupling in Pt/Co Multilayers with Perpendicular Anisotropy

Z.Y. Liu,F. Zhang,N. Li,B. Xu,D.L. Yu,J.L. He,Y.J. Tian 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Measurement of the ICRH antenna phasing using antenna strap probe based diagnostic system in EAST tokamak

Liu L.N.,Liang Q.C.,Yang H.,Zhang X.J.,Yuan S.,Mao Y.Z.,Zhang W.,Zhu G.H.,Wang L.,Qin C.M.,Zhao Y.P.,Cheng Y.,Zhang K. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

To operate the ion cyclotron resonance heating (ICRH) antennas in a better heating state and produce relatively low impurities, it is necessary to control the antenna spectrum by changing the antenna phasing. As the electrical length of the antenna feeding transmission lines is changing as a matter of the standing wave pattern at the ceramic supports, 90 elbows, T-connectors and antenna loops, we chose to measure the current at the grounding points of the antenna loops by antenna strap probe. The voltage drops along a small, several millimeter-long paths at the end of the antenna loops give a signal that is proportional to the current in the antenna loop. Through the simulation of the antenna strap probe and the actual measurement of the antenna phasing under vacuum conditions, the reliability of the antenna strap probe based diagnostic system have been successfully proved. Moreover, this system was successfully applied to the ICRH daily experiments in the spring of 2021. In the near future, the active realtime feedback control of the antenna phasing system will be developed based on this diagnostic system in the EAST tokamak.

Solidification and Evolution of β-NiAl Phase in a Re-Containing Single Crystal Superalloy

Y. M. Li,X. G. Wang,Z. H. Tan,Y. H. Yang,J. L. Liu,J. D. Liu,J. G. Li,Y. Z. Zhou,X. F. Sun 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

The β-NiAl phase, which may exacerbate the high-temperature mechanical properties of Ni-based superalloy, was observedin a designed Re-containing single crystal superalloy. The solidification mechanism of β-NiAl phase and its evolutionafter solution treatment as well as long-term aging at 1120 °C were systematically investigated. The β-NiAl phase wasconfirmed by the analyses of XRD and TEM in as-cast specimen. Combined the analyses of TEM, DSC, phase diagramsand chemical segregation behaviors obtained via EPMA, the solidification path in interdendritic region was determined asL → (β-NiAl + Cr) eutectic, L → β + δ, L + β → γ′, L → γ′. The β-NiAl phase could be diminished by solution treatment and/or long-term aging treatment. After the solution treatment at 1330 °C for 30 min, the β-NiAl phase split into small bulks andthe δ phase dissolved, contributing to the formation of the γ + γ′ structure and large blocky δ phase. During the long-termaging at the 1120 °C, the β-NiAl phase transformed into γ and γ′ phase. With aging time prolonging, the Cr-rich phase dissolved,which promoted the precipitation of TCP confirmed as μ phase with three morphologies.