航空材料学报

THE BEHAVIOUR AND MECHANISM OFTRANSFORMATION OF THE STRENGTHENINGPHASE IN RS Al-Fe-Mo-Zr-Ti ALLOYS

Dai Shenglong, Yu Guifu, Yan Minggao

1995, 15(1): 1-8.

[Abstract](1455) [PDF 2523KB](174)

Abstract:
The behaviour and mechanism of transformation of the strengthening phase in RS Al-Fe-Mo-Si-Zr-Tialloy were studied in detail using TEM, EDX and X-ray diffraction and measurement of accurate lattice pa-rameters. It was found that the transformation is unusual and complex. The process of transformation isnot only related to the temperature.but also to the exposed time at the ternperature. Several phases appearin various shapes and sizes during the process. five of which are proved to be new phases. A new mecha-nism of transformation was put forward according to transformation behaviour and related microstructure.The mechanism indicates that the process of transformation is the process of gradual divorce of Zr,Ti,Mofrom the strengthening Al12(Fe, Mo, Zr, Ti)3Si phase. which occurs during the coarsening of the phase.

SOLID-LIQUID INTERFACE SHAPE AND MORPHOLO-GICAL DEFECTS OF SINGLE CRYSTAL SUPERALLOY

He Guo, Li Jianguo, Mao Xiemin, Fu Hengzhi

1995, 15(1): 9-14.

[Abstract](1458) [PDF 371KB](315)

Abstract:
A series of SC superalloy DD8 samples were directionally solidified in a furnace with high thermal gra-dient and wide velocity scope. And the effects of solidified velocities on the S/L interfacial shape and themorphological defects were gualitatively measured and systematically discussed. The results indicate that aflat S/L interface can be obtained at high cooling rates and low solidified velocities(below critical velocity V*),but concave S/L interface will occur above the V*. The concave interface will lead to the forrnationof low angle boundaries, subgrains, splaying and shrinkage. And the deeper concave interface at high so-lidified velocity will lead to unstable directional solidified processing.

INVESTIGATION OF THERMAL CIRCLING CURVE OFAL UMINUM-MATRIX COMPOSITES FORELECTRONIC PACKAGING

Yu Xuebin, Zhang Guoding, Wu Renjie

1995, 15(1): 15-21.

[Abstract](1421) [PDF 369KB](296)

Abstract:
The effects of thermal circling on the curve of heat expansion and cold contraction are investigated. Itis found that the thermal circling curves of aluminum-matrix composites reinforced with carbon fiber forelectronic packaging are not close. The curve shape and close extent of thermal circling are related to rein-forcernents,sarnple orientation,thermal circling number of times and temperature range. These phenomenaare explained by micro-mechanics.

THE STRENGTHENING MECHANISMS OF HOLE EXPANSION IN TOUGHENING TREATED STEEL 300M

Song Deyu, Luo Zhiping, Zhao Zhenye

1995, 15(1): 22-27.

[Abstract](1381) [PDF 385KB](226)

Abstract:
The strengthening mechanisms of hole expansion in toughening treated steel 3 00M have been studiedby x-ray diffractometer and TEM. It was shown that the fatigue strength was improved from σ0.1=410MPa to σ0.1=530 MPa after the expansion. The strengthening mechanisms came from many aspects, in-cluding the formation of residual compressive stress, the tension and compression of crystal plane, thebending and distortion of crystal lattice, the increase of dislocation density,the formation of cellular dislo-cations, the transformation of part of the residual austenite to deformation martensite, and the decrease ofthe hole surface roughness,Due to the comprehensive effects of these factors during the fatigue test, thefatigue strengths was thus improved.

INVESTIGATION OF MECHANICAL PROPERTIES OF HIGH ALLOYING Al-Si ALLOY IN ROOM AND HIGH TEMPERATURE CONDITION

Li Peijie, Gui Manchang, Jia Jun, Li Qingchun, Zhu Jian

1995, 15(1): 28-34.

[Abstract](1386) [PDF 417KB](183)

Abstract:
The microstructures and mechanical properties of high temperature and short exposing time tensilesamples of cast AlSi6Cu2Mg alloy are analyzed by TEM and SEM. With appropriate content alloyimg elements, the mechanical properties of the alloy at room temperature, meanwhile,the high temperaturestrength can be improved due to retardation of accumulation and growth of Mg2Si phase.

THE HREM STUDY OF THE PRECIPITATES IN AN Al-Zn-Mg ALLOY

Jiao Huisheng, Li Chunzhi

1995, 15(1): 35-38.

[Abstract](1343) [PDF 284KB](225)

Abstract:
A study of precipitate phases in an Al-Zn-Mg alloy in the T74 condition has been conducted by meansof high resolution electron microscopy. It has been observed that G.P. zones,η′ and η phases exist simultaneously in the matrix. The G.P. zones are plate-like forming on (111) matrix plane. The η′ phase has ahexagonal structure with a=0.496nm,c=1.403nm and the orientation relationship with the matrix is (001)η//(111)m,[120]η//[110]m.A new orientation relationship between the η phase and the matrix isfound to be (001)η//(111)m,[120]η//[110]m.

A UNIFIED VISCOPLASTIC DAMAGE CONSTITUTIVE MODEL FOR CREEP ANALYSIS

Li Zhenhuan, Zhang Keshi

1995, 15(1): 39-44,34.

[Abstract](1543) [PDF 2521KB](151)

Abstract:
By means of strain effective hypothesis,a damage internal variable was included the unified viscoplas-tic constitutive model possessing overstress characteristics proposed by the authOrs in this paper, and anew damage model based on combinatory work density concept has been suggested. Compared with otherphenomenal model,it has a clearer micro physical meaning, can reflect the effect of strain rate and stressstate on the damage,and can be used to describle the three phase of creep.

INFLUENCE OF SYNTHESISING TECHNOLOGY ON DIAMOND FILMING QUALITY

Huo Xiao, Ren Jialie, Lu Anli

1995, 15(1): 45-50.

[Abstract](1378) [PDF 349KB](144)

Abstract:
The influence of synthesising technology on the nucleation of diamond film deposited by microwaveplasma CVD was investigated. The effect of substrate’s position in the plasma, substrate holder styles, H2 plasma pretreatment and start-up conditions on diamond nucleation uniformity was discussed in detail. Finally, a set of synthesis procedure to assure formation of uniform diamond film had been established.

THE INVESTIGATION OF HIGH TEMPERATURE FATIGUE CRACK GROWTH RATES da/dN IN ALLOY DA4169

Xie Jizhou, Shen Zhumin

1995, 15(1): 51-55,50.

[Abstract](1434) [PDF 325KB](119)

Abstract:
The fatigue crack growth behaviours of alloy DA4169 in direct ageing were studied at 550℃, 650℃,and the experiment of hold time on peak load was also carried out.The experimental resuIts show that theda/dN value in continual cycle is basically the same as conventional 4169,while it is a little better at 650℃.The da/dN value with 15s hold time on upon peak load at 650℃ appears more rapidly than that of continual cycle.

THE CHARACTERIZING PARAMETERS OF IMPACT RESISTANCE DAMAGE COMPOSITE LAMINATES

Zhang Yanzhong, Ning Rongchang

1995, 15(1): 56-62.

[Abstract](1383) [PDF 406KB](271)

Abstract:
For the CFRP composite laminates with quasi-isotropic ply sequences of [02/902/452/-452]s, whichis often available in airplane,the characterizing problems on the damage caused by low velocity impact areinvestigated in this paper. The parameter alteration of the laminates before and after impact may be char-acterized by damage degree D which is induced by drop-weight impact tests. Three characterizing parame-ters determined by quasi-static bending tests-intraply cracking critical energy E1c, interlaminer crack-ing (delamination) critical energy E2c and delamination progating resistance R are given to judge the impactresistance of the CFRP composites. These characterizing parameters are valuable for the design of thedamage tolerance of composite structures and components as well as the development of composites withhigh impact resistance.

1995 Vol. 15, No. 1