航空材料学报

MICROSTRUCTURE AND HIGH TEMPERATURE COMPRESSION BEHAVIOR OF Ti 48Al PST CRYSTALS

Lin Jianguo, Zhou Yajian, Zhang Yonggang, Chen Changqi

1998, 18(1): 1-6.

[Abstract](1360) [PDF 242KB](179)

Abstract:
Ti-48at%Al crystals containing a single set of lamellae with parallel planes (PST crystal) were grown by a magnetically suspended flowing zone method.The compressive yield stress of PST crystals was measured at 800℃.The results show that the compressive yield stress of the PST crystal depends on the angle between the lamellar boundaries and compressive axis.The yield stress is lowest for =45°,and highest for =90°.The yield stress for =90° decreasing by a big margin at 800℃ is related to the decrease of the CRSS for {1121}〈1126〉.

A STUDY OF AGING CHARACTERIZATION OF Ti 15 3 ALLOY

Wang Qingru, Ma Jimin, Zhang Qingling

1998, 18(1): 7-14.

[Abstract](1358) [PDF 292KB](254)

Abstract:
The relationship between aging temperature,time,Al equivalent and mechanical properties of Ti-15-3 (Ti-15V-3Cr-3Sn-3Al) alloy at different heats was investigated.The variety of tensile strength with aging temperature is characterized by a linear relationship at the temperature range of 500～540℃,and the average slope is about(-3MPa/℃).The linear equation between strength and Al equivalent has been obtained,and the optimum Al content is calculated as 3.1%～3.3%.The relationship between strength and ductility was studied by statistical method,and the effect of cold processing on aging characterization was also investigated.The studied aging treatment 520℃/10h/AC reaching the strength grade 1080MPa possessies satisfactory mechanical properties,and this aging treatment was applied to manufacturing a decelerating umbrella beam of aircraft.

TENSILE FRACTURE BEHAVIOUR OF SINGLE CRYSTAL ORIENTATION DD100 AT SLOW STRAIN RATE AT HIGH TEMPERATURE

Zhou Candong, Dong Xianping, Yu Jinxing, Zhang Yuanhu, Yuan Fuhe, Zhou Longjiang, Li Tiefan, Sun Chuanqi, Li Qijuan, Wu Changxin, Liu Zeyao

1998, 18(1): 15-22.

[Abstract](1437) [PDF 540KB](229)

Abstract:
An investigation has been made of tensile fracture behavior of single crystal orientation DD100 at slow strain at high temperature.Oxygen in air has little influence on the properties of DD100 at 760℃ and the strengths of DD100 at 850℃,but it made the tensile elongation of DD100 reduce at 850℃ as compared with it in vacuum.Oxygen did not affect the fracture of DD100 but strongly influenced the propagation of the crack at the specimen surface.The main crack sources lied in the margin of fracture surface in air and were situated in the middle region of fracture surface in vacuum.Both in vacuum and in air,the tensile fractures of DD100 have many holes surrounded by square facets.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF SPRAY DEPOSITED SUPERALLOY

Mi Guofa, Li Zhou, Zhang Zhihui, Liu Zhongwu, Zhang Guoqing, Tian Shifan

1998, 18(1): 23-28.

[Abstract](1349) [PDF 223KB](241)

Abstract:
The technique of preparing three typical superalloy deposits is introduced.The microstructure and the mechanical properties were analysed and tested.The results indicate that the deposits are integrally dense,and have a low oxygen content,homogeneous chemistry,a refined microstructure,and preferable mechanical properties.

EFFECT OF LASER FORMED HOLES ON STRESS RUPTURE PROPERTIES OF A DIRECTIONALLY SOLIDIFIED SUPERALLOY

Zhang Hongwei, Chen Rongzhang

1998, 18(1): 29-31,50.

[Abstract](1401) [PDF 196KB](178)

Abstract:
The effect of laser-formed holes on the thin-wall stress-rupture properties of a directionally solidified superalloy is studied by using tubular thin-wall specimens (δ=1.2mm) with shape and thickness similar to the hollow turbine blades made by the near-shape investment cast procedure. The results show that stress-rupture properties of specimens with one row of holes do not reduce remarkably and that of those with two row of holes reduce slightly, comparing that of ones without holes. It is found that the microstructure are not influenced by the holes and the net loading area reduce slightly as in these specimens with two row of holes.

MECHANISM OF TEMPER EMBRITTLEMENT IN 16NiCo STEEL

Zhong Ping, Gu Baozhu, Jin Jianjun, Wang Hongtao

1998, 18(1): 32-38.

[Abstract](1436) [PDF 274KB](393)

Abstract:
The tempering process of 16NiCo steel has been studied by means of SEM,TEM and Auger spectrocopy.The results show that one-step temper embrittlement (OSTE) occurs at 440℃.The fracture path is qusi-cleavage.It is caused by inter lath films of Fe3C and M3C carbides.Tempering at 550℃ results in a second drop in impact toughness.This tempered embrittllement is reversible. It is due to impurity (P) segregation to prior austenite grain boundaries leading to intergranular fracture.

INVESTIGATIONS ON THE OPTIMIZATION OF COLD PRESSING OF Ag CLAD Bi 2223 SUPERCONDUCTING TAPES

Ma Yanwei, Wang Xianjin, Wang Zutang

1998, 18(1): 39-44.

[Abstract](1383) [PDF 226KB](179)

Abstract:
Optimum procedures of cold pressing of Bi-2223 Ag-clad superconducting tapes fabricated by Powder-in-tube method were investigated.Cold pressing was necessary to produce tapes with good texture and high J C values.The optimum technical parameters are sintering three times at 838℃ for 60h and pressing twice with pressure 2.0GPa and 2.5GPa for the first and second compaction respectively.Reduction rate of cold pressing was 1.75×10-4 mm/s.Meanwhile,experimental results exhibited that high density and degree of grain alignment of the tapes were mainly attributed to cold pressing.

THE INFLUENCE OF THE Cr CONTENT AND STRUCTURE IN NiCrAlY COATINGS ON ITS LIFE OF HOT CORROSION RESISTANCE

Fan Ruilin

1998, 18(1): 45-50.

[Abstract](1359) [PDF 225KB](193)

Abstract:
Three kinds of Cr content and different structure in NiCrAlY coatings and their hot corrosion resistance has been studied in the paper.It is found that the average life of hot corrosion resistance of the coating rises 40 percent when Cr content in coating increases 2 percent. However, the life of the coating rises 2 to 3 times with suitable coatings structure at the same content.

THE DEVELOPMENT OF A THIN ONE LAYER RADAR ABSORBING COATING FOR X AND Ku BANDS

Wang Zhiyong, Xiong Kemin, Liu Junneng, Ren Shufang, Xing Liying, Deng Longjiang

1998, 18(1): 51-55.

[Abstract](1462) [PDF 187KB](265)

Abstract:
A new kind of radar absorbing coating is developed.The thickness of this coating is not more than 0.5mm, and less than -4dB reflectivity for normally incident energy can be obtained within a wide range of 8～18GHz.The coating,whose comprehesive properties are very high,is an applicable stealth material for aircrafts.

SIMULATION OF SIMPLIFIED EPOXY MOLECULES IN TEMPERATURE FLUCTUATION AT 400K

Tang Bangming

1998, 18(1): 56-62.

[Abstract](1364) [PDF 252KB](170)

Abstract:
Based on the structure of tetraglycidyldiaminodiphenylmethane(TGDDM),series of simplified epoxy molecules are constructed by substituting the hydrogens at phenyls with side groups or segment between two phenyls with different sub-structures in this paper.Parameters of these molecules such as bond length,bond angle,torsion angle and non bonded distance in the temperature fluctuation at 400K are simulated dynamicly. The change in the temperature fluctuation of these parameters are analyzed.The stabilities of these molecules characterized by parameters mentioned above are also discussed.The conclusion showed that the-CO-substructures between two phenyls are the best for the stability of molecules based on TGDDM.

1998 Vol. 18, No. 1