航空材料学报

SKIN EFFECT OF Hf-RICH MELTS IN Hf-BEARING CAST NICKEL BASE SUPERALLOYS

Zheng Yunrong

1988, 8(2): 1-7.

[Abstract](1397) [PDF 2096KB](236)

Abstract:
Hf-rich melts often flow out from surface of cast or heat treatment parts along the capillary channels of interdendrites and form a Hf-rich liquid film when Hf-bearing cast nickel base superalloys melt or solidify in temperature range of 1250～1290℃.The liquid film has a"seelf recovery effect"to the cracks formed,therefore improves the weldability of Hf-bearing alloys obviously.The number and density of cracks in alloy with H-f are a magnitude order lower than ones in alloy without Hf.Skin liquid can also react with sell mold and form a layer of HfO2.

A STUDY OF MECHANISM OF OVERAGE BEHAVIOR IN A SECONDARY HARDENING STEEL

Zhao Zhenye, Zhong Bingwen

1988, 8(2): 8-13.

[Abstract](1365) [PDF 1130KB](191)

Abstract:
The overage behavior existing in Cr-Mo-V secondary hardening high strength steel during tempering in the range of 620-640℃ has been investigated.Its mechanical behavior displays a trough on the curve of the U-notch impact toughness and an increase in fracture toughness with the decreasing of the tensile strength.This trough is related to the decrease of the impact initiaton energy.The coarsing of the carbides,which are segregated along grain boundaries,martensite packet boundaries and interfaces between martensite laths is the cause of the overage phenomenon.A combination mechanism model which can explain the contradiction behavior betweer the impact value and the fracture toughness has been suggested.

EFFECT OF Pre-HIP HEAT TREATMENT OF ALLOY POWDER ON PPB CARBIDE PRECIPITATION OF P/M RENE'95 SUPERALLOY

Mao Jian, Yu Kelan, Zhou Ruifa

1988, 8(2): 14-18,24.

[Abstract](1402) [PDF 980KB](156)

Abstract:
The effect of various Pre-HIP heat treatments on the size and distribution of Prior Particle Boundary(PPB)carbide precipitaties,γ'volume fraction and grain size of HIP billets of Rene'95 PM alloy has been studied.And the possibility of the elimitation of PPB carbide segregation by using pre-HIP heat treatment has been explored.The results show that pre-HIP heat treatment canreduce the degree of PPB carbide segregation,increase the γ'volume fraction,but leave the grain size unchanged.This is mainly due to the changes in Pre-HIP powder surface state,and precipitating enviornment of carbides on PPB.

CHARACTERS OF SOLIDIFICATION AND CRYSTALLIZED MICROSTRUCTURE OF Al-Li ALLOY IN THE MICROGRAVITY CONDITION

Qiang Jun, Pan Mingxiang, Wu Yilei

1988, 8(2): 19-24.

[Abstract](1365) [PDF 989KB](270)

Abstract:
Comparison investigation of Al-Li alloy specimens melted and solidified in the reentrant satellite and on the earth was carried out with optical metallo-graphy,TEM,SEM,Auger electron spectrometry and X-ray diffraction.It was found that to compare with the specimen on the earth the specimen solidified in the microgravity condition had less and concentrited shrinkage,coarser surface,larger grains,more T1(Al2CuLi)phase and less AlCu4 phase.Some of the reasons for the differences were discussed.

A STUDY ON EPON/DICY-PSF-PPO POLYBLEND ADHESIVE SYSTEM

Cai Jianfen, Zheng Ruiqi, Fan Tang

1988, 8(2): 25-32.

[Abstract](1396) [PDF 2037KB](193)

Abstract:
The introduction of PPO into Epon/Dicy-PSF system with Epon/Dicy-PSF-PPO being a certain ratio can increase the peel strength within the temperature range of-55—175℃ by 15%,and decrease the initial crack length in wedge test by 5mm and the crack growth rate to a great extent while keeping its shear sterngth,temperature resistance and hydro-thermal aging resistance the same as those of adhesive SY-14,the results of stress-strain test show that the fracture stress increasds by 30%,the elongation to break 33% and fracture energy 82%,In thesystem only chemical reaction between Epon and Dicy takes place,there by a three dimensional network is formed.While Epon,PSF and PPO are partly compatible and their molecular chains diffuse and get cntargled with each oth-er.Further more,PPO,PSF are of high tensile strength and good toughness,thus a macrohomoganeous but microheterogeneous IPN polyblend system is formed,the toughening mechanism of the system is explored briefly.

THE INFLUENCE OF RARE-EARTH ELEMENT LANTHANUM ON THE ENDURANCE LIFE OF Ti-6242S

Wu Chongzhou, Xue Zhixiang

1988, 8(2): 33-38.

[Abstract](1424) [PDF 1479KB](157)

Abstract:
The influence of rare-earth element lanthanum on the endurance life of Ti-6Al-2Sn-4Zr-2Mo-0.1Si was studied and some mechanisms were also proposed.Expe-riments show that with the addition of lanthanum,colony becomes fine,the num-ber of colony boundary increases and some small La2O3 particles precipitate in the matrix.All these factors make the movement of dislocations more difficult.So the endurance life of this ailoy gets prolongel.Alloying element silicon can increase creep resistance,with the help of Si and La,the endurance life can be further increased.

MICROSTRUCTURAL INFLUENCE ON LOW-CYCLE FATIGUE DWELL-EFFECT OF TC11 WROUGHT TITANIUM ALLOY

Kou Chouqi, Cao Chunxiao

1988, 8(2): 39-45.

[Abstract](1420) [PDF 2369KB](160)

Abstract:
The influence of four kinds of microstructures in TC11 wrought titanium alloy on the low-cycle fatigue dwell effect has been investigated.The experimental result shows that the low-cycle fatigue dwell effect of the basket-weave structure is much weaker than that of the other three kinds of structures.

INVESTIGATION OF PEEL STRENGTH OF ADHESIVE BONDS

Yi Xiaosu

1988, 8(2): 46-50.

[Abstract](1401) [PDF 369KB](111)

Abstract:
The"BELL" and"T"specimens for peel tests can be both used to compare relative strengths of adhesives and as a process inspection tool for surface preparation,but the"BELL"test is for this reason scnsitiver.Because of the friction of the floating roller,a larger peel force is required by"BELL" specimens than"T"specimens' the failure layer is near the interface.The strong acoustic emission is recorded at the initiation of failure.A peeling speed of 80 to 100 mm/min is recommended.

RELAXATION MODEL OF RESIDUAL STRESS BY SURFACE DEFORMING STRENGTHENING AND ITS EFFECT ON THE FATIGUE RESISTANCE

Li Jinkui, Yao Mei, Wang Renzhi

1988, 8(2): 51-60.

[Abstract](1425) [PDF 673KB](189)

Abstract:
The different relaxation models of residual stress produced by surface defor-ming strengthening during the static and alternating load have been discussed and evaluated.The effect of compressive residual stress produced by shot peening and its relaxation on the fatigue crack nucleation,fatigue crack propagation and fa-tigue propagation threshold have been presented and discussed.Finally,the opti-mum compressive residual stress field and the relationship between the residual stress field and the fatigue resistance have been introduced.

A STUDY OF THE PROCESSING OF ALUMINIUM ALLOY POWDER PRODUCED BY A SUPERSONIC GAS ATOMIZER

Chai Shichang, Li Yuren, Wang Tianzhen, Yu Guifu, Yan Minggao

1988, 8(2): 61-65.

[Abstract](1422) [PDF 432KB](149)

Abstract:
The effect of the processes and the geometry size of the jet on the particle size distribution and appearance of rapidly solidified Al-5.6Zn-2.2Mg-1.7Cu-0.12 Mn-0.6Co-0.5Zr-0.3Ti alloy powder produced by a supersonic gas atomizer was investigated.The relationship between size and solidification rate of the Pow-der was also studied.The alloy powder produced by a supersonic gas atomizer exhibited fairly-good spherical appearance,the proportion of powder is the size ranged from 40 to 200μm was estimated to be 90 percent(weight)with the average diameter of about 60μm,and the cooling rate of the powder was 105-103K/sec.During ato-mizing the liquid alloy temperatuure was 820℃ and the gas atomizing pressure was 3Mpa.

THE RELATIONSHIP BETWEEN FRACTURE MORPHOLOGY AND EXTRUSION RATE IN RAPIDLY SOLIDIFIED P/M ALUMINUM ALLOY

Feng Yushu, Li Yuren, Huang Huiyuan

1988, 8(2): 66-70.

[Abstract](1366) [PDF 1764KB](155)

Abstract:
The relationship between fracture morphology and extrusion rate in rapidly solidified P/M aluminium alloy was investigated.The fracture morphology appeared to be interpartical substantially under extrusion rate of 10:1,and it was found to be transgranular under extrusion rate of 25:1 or more than.

THE INFLUENCE OF PHYSICOCHEMICAL PROPERTIES OF WATER DISPLACING ADDITIVE ON THE CAPABILITY OF REMOVING WATER FROM METAL SURFACE

Lu Feng, Tang Junqi, Situ Zhenming

1988, 8(2): 71-79.

[Abstract](1513) [PDF 739KB](171)

Abstract:
The mechanism of water displacement has been studied in present investi-gation,and some effective test method for studing water displacement has be-en proposed.By means of determining and caculating water displacing time,surface and interracial tension,contact angle and ESCA for determining action and ef-fect between the water displacing additive and the metal surface some import-ant conclusions have been made:good water displacing additives can greatly de-crease oil/water,oil/metal irterfacial tension and make the contact angle in-crease to at least above 90°,water displacing additive is slightly soluble in wa-ter and has some action with metal surface.Finally,if additive has good emul-sibility,it will affect the efficiency of water displacement from a metal surface.And an equipmet which can quantitatively determine water displacing time and sift water displacing additive simply has been designed.

1988 Vol. 8, No. 2