航空材料学报

AN INVESTIGATION ON THE REFINEMENT OF COARSE WIDMANSTATTEN STRUCTURE OF Ti-6A1-4V ALLOY CASTINGS

Zhang Fan, Zhang Bao-chang, He Ming, Xue Zhi-yang, Wang Jin-you

1985, 5(2): 1-7.

[Abstract](1247) [PDF 3776KB](70)

Abstract:
In this present work, effects of heat treatment on the microstructure and mechanical properties of Ti-6Al-4V alloy castings have been studied and the optimum heat treatment regime for refining the coarse Widmanstatten structure of the alloy is proposed as follows:t+(5~15℃)/10min WQ+970℃ /10min750℃/10min,cycling five times，AC from 750~800℃.By means of this regime，the coarse Widmanstatten structure of the alloy way changed into basketwave structure.Compared with the mechanical properties of as-casted alloy, the elongation and reduction in area were increased by 144% and87% respectively, while the tensile strengh had only dropped by 4%.The low cycle fatigue life was doubled.The impact toughness, high temperature tensile properties, heat stability and high cycle fatigue life were all enhanced to different extent.Quenching the specimen from phase region followed by annealing at 850℃ for 2~24 hours have also obtained good comprehensive mechanical properties.Compared with the properties of as casted alloy,the elongation and reduction in area were raised by 117% and 75% separately,while the tensile strengh didn/t dron or even rised sliehtly.

THE EFFECT OF COOLING RATE. AND REFINING ELEMENTS ON THE DENDRITE ARM SPACINGS AND N1ECHANICAL PROPERTIES

Xu Cai-lu, Zhu Yun-hao

1985, 5(2): 8-15.

[Abstract](1219) [PDF 4214KB](63)

Abstract:
The effect of cooling rate and refining elements on the dendrite arm spacings and mechanical properties of Al-5.0Cu alloys has been in pesiigated in present work.The results show that the dendrite arm spacings in all alloys used is inversely proportional to the cooling rate，the linear relationship between the togarithms of spacings and cooling rate is clearly re、Baled.And refining elements have evident influence on the dendrite arm spacings.The addition of refining ele-menu, at same cooling rate，will reduce the dendrite arm spacings, when the cooling rate changes，the sensitivity of alloys with refining elements to the cooling rate is decreased.The cause of the phenomenon is the restricting action of refining elements on the growth of dendrites.The relationship between mechanical properties and the dendrite arm spacings for ZL201 and ZL202 alloys,simultaneously.is studied.The experiment reveal that the ultimate tensile strength and elongation of two alloys decrease linearly，with inereasing the dendrite arm spacings，while the yield strength of two aloy specimens remains essentially unaffcted by the change in the dendrite arm spacings.

STUDY ON THE COMPATIBILITY OF PRIMER AND ADHESIVES

Zhu Li-hua, Fan Tang, Zheng Rui-qi

1985, 5(2): 16-22.

[Abstract](1161) [PDF 3822KB](74)

Abstract:
When primer adhesive system is used to bond aluminium alloys，primer thickness has obvious effects on the bonding strength，especially on low temperature peel strength.Generally，when primer thickness exceeds certain value，the low temperature peel strencth will decrease obviously.These effects reflect the compatibility of the primer and the adhesive.In this paper, the effccts of the chemical composition and degree of pre-curing of the primer and the composition and mechanical properties of the adhesive on the compatibility of the primer and the adhesive are studied and thereby the factors influencing the susceptibility of bonding strength on primer thickness and the wav of reducing the susceptibility of bonding strength on primer thickness are discussed

THE EFFECT OF MICROSTRUCTURES ON FATIGUE CRACK PROPAGA'T'ION RATE IN TC6 TITANIUM ALLOT

Tao Chun-hu, Zhang Shao-qing

1985, 5(2): 23-29.

[Abstract](1161) [PDF 3962KB](74)

Abstract:
This paper presents the result of an investigation on fatigue crack propagation rates (da/dN) at room and 400℃ for four conventional microstructures in a TC6 titanium alloy.The fatigue propagation paths and the plastic zone round fatigue crack tip in fatigue tested specimens have been observed by means of OM and SEM, The microstructure types are eztremely sensitive to da/dN at room temperature.To sum up，at room temperature the microstructures in sensitive to da/dN order is as follows:duplex, equiaxed, basket-weave and Wdmanstatten.The microstructure is not sensitive to da/dN at 400℃.Because there is littledifference in plastic zone around fatigue crack tip for four microstructures.The crack propagation in specimens with Widmanstatten and basket-weave micr ostructures was proceeded by cross-cutting - phase boundary along slip bands,The coarse grain boundary a phase presented much impedance to sliping and crack propagating at room temperature while there was little impedance to them at 400℃.Because there is little. difference in plastic zone around fatigue crack tip for four microstructures.The crack propagation in specimens with Widmanstatten and basket-weave microstructures was proceeded by cross-cutting - phase boundary along slip bands,The coarse grain boundary a phase presented much impedance to sliping and crack propagating at room temperature while there was little impedance to them at 400℃.Many voids appeared in front of the fatigue crack tip in specimen with equiazed and duplex microstructures.Crack propagated by linking-up of voids by the way of renucleation mechanism.

THE EFFECT OF ALLOYING ELEMENTS ON WELDING-SOLIDIFICATION-CRACK SENSITIVITY OF GH99 ALLOY

Ke Ming, Duan Shi-xun, Zhang Yan-sheng

1985, 5(2): 30-35.

[Abstract](1182) [PDF 3947KB](79)

Abstract:
The welding-solidification-crack sensitivity of GH99 alloy has been studied,Cruciform test and Tigamajig test were used for the evaluation of effect of A1/Ti ratio on the welding-solidification-crack sentivity in five feats of slightly different compositions, The microstructure was studied by optical and electron metallography and the composition of fracture was examined with Auger electron spectroscopy and energy-dispersive electron microanalysis.The mechanism of welding-solidification-crack of GH99 alloy was investigated,The result have shown that the welding-solidification-crack sensitivity of CGH99 alloy depends strongly on its A1 and Ti contents，and shows a minimum when A1/Ti=1 .7.When the A1/Ti is fixed, the higher is the Al+Ti value,the larger is the welding-solidification-crack sensitivity, The cracks is caused by the formation of a liquid film of a Ti-rich low melting point constituent due to its segregation between dendrites.

THE EFFECTS OF HAZ LIQUATED ON THE HYDROGEN-INDUCEd

Zhang Ming, Zhang Yan-sheng

1985, 5(2): 36-41.

[Abstract](1162) [PDF 3685KB](72)

Abstract:
In this paper, occurcnc condition of HAZ liquated micro-cracking and its effects on hydrogen-induced cracking in ultra-high strength steel GC4 were investigated with dynamic thermal simulation test and hydrogen charged slowtensile test.It was found that the occurence of liquated cracking is mainly depended on the time range in which the HAZ stay at high temperature and the segragation degree of base metal.Moreover, HAZ liquaced micro-cracks will become the starting position or the propagating pathes of hydrogen-induced cracking, and promotes the hydrogen embrittlemcnt during later process

AN INVESTIGATION ON THE BEHAVIOR OF COMBINATION OF HIGH AND LOW CYCLE FATIGUE FOR GH36 ALLOY AT ELEVATED TEMPERATURE

Wang Zhang-an, Ouyang-Jie, Song De-yu, Yan Ming-gao

1985, 5(2): 42-47.

[Abstract](1190) [PDF 3568KB](71)

Abstract:
In this investigation the behaviors of low cycle fatigue.LCF, high cycle fatigue,HCF,and combined fatigue of LCF and HCF,CF,of a turbine disc material GH36,at 600℃ were studied,The results inducated that the high cycle loading had a certain strengthening effect upon the LCF when the stress ratio Q, Q=2,HCF/,max,LCF,was less than a critical value,Qc.The lives of combined fatigue specimens became shorter than that of LCF when Q was higher than the critical value.The fracture surface of the fatigue semples were observed and analysed by means of micro-fractographic methods.It is found that the failure mechanism changes from creep-fatigue in HCF and LCF separately into combined fatigue as Q value increases and the fracture surface of the tenon tooth of turbine disc is very similer to that of CF specimens.It appears that the damage of the tenon tooth is induced by a combined action of high cycle,vibration,and low cycle，aircraft take off-cruise-landing, loads.

THE INVESTIGATION OF ACOUSTIC EMISSION CHARACTERISTICS OF ALUMINIUM ALLOY LC9

Yang Min, Li Chun-yan, Deng Ri-hong

1985, 5(2): 48-53.

[Abstract](1183) [PDF 3750KB](53)

Abstract:
This paper studied the characteristics of acoustic emission during the dciormation of aluminium alloy LC9, by means of comparing various heat-treat states,as w ell as various strain rates.The results show that the AE characteristics of LC9 aluminium alloy is determined by the heat-treat state of alloy and the strain rate of de for m ation;the crack of inter metallic compounds have little influence

THE EFFECT OF SILICON ON THE HOT CORROSION RESISTANCE OF THE AI-Si COATING

Zhang Yi-fan, Du Fa-yi, Xiao Xu-chang

1985, 5(2): 54-61.

[Abstract](1309) [PDF 4636KB](56)

Abstract:
The hot corrosion behavior of the alu minide coatings contained different conteat of silicon has been investigated in this paper.The results of the in vesitigation showed that，in givea eztent of silicon content，the hot corrosion resistance of the A1-Si coatings increased with increasing of silicon content.The analysis results showed that the major reason why silicon enhance the hot.corrosion resistance of the coatings was due to the formation of amorphous silica whick reacted with the melting salt deposited on the surface of materialsand decreased the ozide ion concentration of the melting salt therefore retarded the basic flu xing of the protective ozide scale.Besides this，the tungsten and molybdenum in the coatings were restricted by the silion to the inner zone of the coatings，w hick inhibited the acidic flu ring attack.

MICROMECHANISM DURING HIGH TEMPERATURE CREEP OF TWO-PHASE ALLOYS

Han Ya-fang

1985, 5(2): 62-70.

[Abstract](1363) [PDF 5897KB](63)

Abstract:
The creep resistance of metals and alloys can be effectively by the introduction of second phase particles.This increment can be attributed to the inhibition of second phase particles to dislocation motion and retentation of dispersed second phase to thermal recovery which is the rate-controlling process during high to m perature creep.Tlie theoretical models of steady state creep inhibition of and back stress during creep of two-phase alloys have been briefly discussed in this review.

THE LOW-CYCLE FATIGUE BEHAVIORS AT HIGH TEMPERATURE FOR ALLOY DZ4

Xie Ji-zhou

1985, 5(2): 71-75.

[Abstract](1186) [PDF 3082KB](57)

Abstract:

FINE STRUCTURE CHANGE IN SHOT PEENING AND EXTRUSION

Zhong Bing-wen

1985, 5(2): 76-78.

[Abstract](1139) [PDF 15827KB](57)

Abstract:

1985 Vol. 5, No. 2