航空材料学报

INFLUENCES OF TRACE ADDITION OF Na,Sr,OR P ON NUCLEATION AND GROWTH OF STAR-SHAPED PRIMARY SILICON IN Al-22%Si ALLOY

Gui Manchang, Jia Jun, Li Qingchun

1997, 17(4): 1-7.

[Abstract](1591) [PDF 271KB](317)

Abstract:
The influences of trace addition of Na, Sr, or P on the nucleation and growth of primary silicon in Al-22%Si alloy fabricated by high pure aluminum and silicon, in which the primary silicon mainly appeared in five petal star-shaped morphology, were studied. Na strongly restrained the fivefold twinning agglomeration of Si clusters, and retarded the nucleation of the five petal star-shaped primary silicon. Meanwhile Na also influenced the growth of the primary silicon. Sr hardly restrained the agglomeration of Si clusters by which the nuclei of five petal star-shaped primary silicon can be formed. During the growth of primary silicon, Sr embedded the growing surface and induced more twin, to result in the change of the morphology of five petal star-shaped primary silicon. P formed AlP in the hypereutectic melt, and promoted the nucleation of primary silicon, but it had no affection on the growth of primary silicon.

STUDY OF THE INTERFACIAL SOLID REACTION BETWEEN THE Ti₃Al SUBSTRATES AND THE NiCrAlY COATINGS

Wang Xiaohong, Liu Haiping, Hao Shanshan, Feng Zixiu, Li Jingui

1997, 17(4): 8-14.

[Abstract](1474) [PDF 265KB](268)

Abstract:
The effect of heat treatment time and temperature the interfacial reaction between NiCrAlY coatings and Ti3Al substrates have been investigated. The Ti3Al substrates were coated with catholic arc ion plated NiCrAlY and then heat treated in vaccum at different temperature and length of time. SEM observation and EDS、EMPA、XRD analysis results showed that:there were great difference in the interfacial reaction between under and above 870℃.Typical solid reaction occurred after heat treatment at 870℃or above. An investigation of the interfacial reaction suggested that the decisive factors were different at different temperature period and at different part of the interface.

EFFECT OF THERMAL EXPOSRURE ON THE MICROSTRUCTURES AND TENSILE PROPERTIES OF HIGH TEMPERATURE TITANIUM ALLOY IMI834

Cui Wenfang, Bian Weimin, Luo Guozhen, Hong Quan, Zhou Lian

1997, 17(4): 15-20.

[Abstract](1451) [PDF 598KB](342)

Abstract:
The tensile priperties of IMI834 alloy were measured after thermal exposures in air at temperatures between 600 and 750℃ for time up to 100 hrs .All of the specimens with oxidized surface exhibited drastical reduction in the ductilities ,while the oxygen-rich scales were removed, the specimens displayed the ductilities in varing degrees. Examinations using optical, scanning and analytical transmission microscopy have shown that oxygen-rich scale on the surface of alloy cause brittle cleavage fracture. The precipitation of ordered α2 phase (Ti3Al) in the alloy exposured at 600℃ developes heterogeneous plannar slip within α plates, and silicides on the α plate bounderies enhance the tendency for plannar slip. The fracture facet exhibites the characteristic of lamellar along α platelet colony. The higher the exposure temperature is , the less the amount of α2 phase within α platelet is ,and the better the ductilty matrix shows. However, if the exposure temperature is above 700℃,both coarser silicides and α2 precipitates will also decrease the strength and ductility of the alloy. 

GROWTH OF PRIMARY α PHASES IN Ti-60 ALLOY AFTER HEAT TREATMENT

Li Geping, Li Dong, Liu Yuyin, Wang Qingjang, Guan Shaoxuan, Li Qingchun

1997, 17(4): 21-24.

[Abstract](1092) [PDF 158KB](246)

Abstract:
The Ti-5.6Al-4.8Sn-2Zr-1Mo-0.32Si-1Nd(Ti-60)high temperature titanium alloy heat treated at 1010℃/2h-WQ and 760℃/2h-AC has been studied. The results of low temperature aging show that the phase boundaries between primary α phase and β transformed phase move into the interior of β transformed phase,and result in bow-shaped phase boundaries. A row of Si and Zr rich particles remains along the phase boundaries in water quenched condition, and some dislocations pinned at the particles are also observed.

EFFECT OF Mn, Zn AND Ag ON THE MICROSTRUCTURES AND TENSILE PROPERTIES OF Al-Mg-Li ALLOYS

Tian Baohui, Lu Zheng, Yan Minggao, Liu Bocao, Wei Bingchen

1997, 17(4): 25-30.

[Abstract](1638) [PDF 373KB](178)

Abstract:
The effect of Mn, Zn and Ag on microstructures and tensile properties of Al-Mg-Li alloys was investigated. The results show that the extent of age hardening and the tensile strength increase, while the plasticity decreases accompanied by increasing transgranular fracture when adding these elements. These behaviors could be related to enrichment of Zn, Ag in δ′ particles and formation of Al6Mn precipitates, respectively.

RELATIONSHIP OF THE LATTICE CONSTANT OF γ PHASE, THE δ CONTENT AND THE AMOUNT OF ALLOYING ELEMENTS IN γ PHASE IN INCONEL718 ALLOY

Liu Wenchang, Yao Mei, Chen Zonglin, Jiang Zhaoqun, Wang Shaogang, Li Weihong

1997, 17(4): 31-36.

[Abstract](1606) [PDF 211KB](286)

Abstract:
The lattice constant of γ phase and the δ phase content in Inconel 718 alloy at 910℃ for different times after cold rollong are measured by X-ray diffraction techniques .The lattice constant of γ phase as a function of the δ phase content, the lattice constant of γ phase as a funciton of the alloying elements of γ phase, and the alloying elements of γ phase as a function of the δ phase content are presented. 

GRAIN BOUNDARY SEGREGATION AND Mg-H INTERACTION DURING CATHODIC H-PERMEATION IN 7175 ALUMINIUM ALLOY

Song Renguo, Geng Ping, Zhang Baojin, Zeng Meiguang

1997, 17(4): 37-43.

[Abstract](1501) [PDF 263KB](303)

Abstract:
The relationship between solid solution Mg segregated on grain boundary and the content of H-permeation in 7175 aluninium alloy under various aging conditions was studied by means of energy spectra, ion mass microprobe analysis and cathodic H-permeation. It was found that the value of H-permeation increases with an increase of the concentration of Mg segregated on grain boundary. This implied that there may exist Mg-H interaction in the process of cathodic H-permeation.

COMPUTER SIMULATION OF ISOTHERMAL FORGING of AS-HIPED RENE′95 ALLOY

Li Yuanchun, Cui jian, Yan Minggao

1997, 17(4): 44-48.

[Abstract](1533) [PDF 208KB](200)

Abstract:
In the present paper, the process of isothermal forging of as-HIPed Rene′95 is simulated by using large deformation rigid-viscoplastic finite element method (FEM). The flowing law and the strain distribution of the workpiece are analyzed. Finally, the importance and advance of design based on simulation is described in comparison with empirical design.

INVESTIGATON ON THE IMPACT DAMAGE AND POST-IMPACT COMPRESSION OF STITCHED COMPOSITES

Chen Wei, Shen Baohua, Wang Binbin, Liu Weiping

1997, 17(4): 49-53.

[Abstract](1501) [PDF 174KB](252)

Abstract:
The stitching process was applied to improve the properties in the through-thickness direction of composites based on prepreg materials. Drop-weight impact damage and compression impact test was couducted. It appears that the damage area size can be decreased by incrasing stitching density and using high strength thread; the CAI strength rises remarkablely when the stitching density was increased instead that high-stremgth thread used. 

STUDY ON MODE Ⅱ INTERLAMINAR FRACTURE TEST METHOD OF COMPOSITES

Yu Zhicheng

1997, 17(4): 54-61.

[Abstract](1510) [PDF 277KB](471)

Abstract:
In this paper,test method of mode Ⅱ interlaminar fracture toughness of composites was studied. The results indicated that crack length should be selected in the range of 0.4≤a/L≤0.85 when using ENF method to determine GⅡC,GⅡCdata obtained from crack tip precrecked with mode Ⅰloading and unprecracked crack tip are great than that from crack tip precracked with mode Ⅱ loading,the crack tips precracked by fatigue and static loading induce same GⅡC results,and the specimen geometry and loading rate have no influence on ENF test results.

1997 Vol. 17, No. 4