航空材料学报

Study on IC-6 superalloy brazing joint micros tructure with Ni-B filler metal

XIE Yong-hui, LIU Xiao-fang, MAO Wei, YAN Ming-gao

2000, 20(1): 1-6.

[Abstract](1462) [PDF 280KB](287)

Abstract:
The brazing joint microstructure of IC-6 superalloy using Ni-B alloy at 1220℃ for different heating time was investigated.The results indicate that γ+γ' can be formed in the brazing seam by the diffusion of Al of IC-6 alloy alone.However,the high temperature stability of γ' is very poor,and a lot of grain boundaries exist in the brazing seam which are harmful to the joint property.There are two kinds of borides formed in the near-seam zone,with different Ni:Mo(at%).The appearance and distribution of the borides will change for different keeping time at the brazing temperature.

Influence of load frequency and heat treatment on fatigue crack propagation rate of die-casting alloy AZ91HP

LIU Zheng, LI Yan-chun, WANG Zhong-guang, WANG Yue, LIU Chong-yang

2000, 20(1): 7-11.

[Abstract](1518) [PDF 676KB](424)

Abstract:
On the condition of preserving the as die casting section,three different die casting magnesium alloys AZ91HP in the states of as dic-cast,solution and peak aging were analyzed,which are tested under different frequency.The result has shown that the fatigue crack propagation rate(FCPR)of die casting magnesium alloy increases with the frequency decreasing.FCPR can be reduced by solution treatment but accelerated by aging.

Investigation of threshold and wide range fatigue crack propagation rates in LY12CZ alloy

DING Chuan-fu, YU Hui, WU Xue-ren

2000, 20(1): 12-17.

[Abstract](1534) [PDF 253KB](291)

Abstract:
The thresholds and wide range fatigue-crack propagation rates in an aluminum alloy,LY12CZ sheet,at three stress ratio(R=0.5,0 and-1)by load-decreasing,load-increasing and constant-load amplitude test procedures were measured The results show that,(1)the da/dN-ΔK curves at each stress ratio showed three transitions and these transitions tend to occur at nearly the same crack-growth rate for all R-ratios tested,(2)the stress ratio against the crack gowth rate relation show a strong correlation,(3)crack-closure was found to be the major factor in causing the correlation of stress ratio with crack growth rate. The crack-opening stress calculated from the closure model was able to correlate fatigue crack growth rate against the effective stress-intensity factor range data quite well over a wide range in rates at three stress ratio(R=-1,0 and 0.5)in the LY12CZ alloy.

Eutectic Si-phase in Al-Si alloy modified by Na-salt

XU Jian-hui, LONG Wen-yuan, FANG Li-gao

2000, 20(1): 18-21,45.

[Abstract](1543) [PDF 646KB](498)

Abstract:
Al-10wt%Si alloy made of high purity aluminum and silicon(>99.99wt%)is modified by Na-salt.The result from analyzing the eutectic Si-phase indicates that the Si-phase lags behind the Al-phase when Al-Si alloy eutectic solidified.Modification not only changes the laminar Si-phase to fibrous Si-phase whose solidification lagged more than the former's,but also increases greatly the density of twin crystal in Si-phase.The twin crystal axis is(111)Si.The crystal orientation is(211)Si.The two phase,Si-phase and Al-phase in eutectic,accord with a regulation that [100]Al parallels to [110] Si.Further more,the modified eutectic Si-phase branches,refines,flexes in accordance with TPRE growing-mechanism,which is an important approach to form modified crystallization structure.

Precipitation study of gamma prime in continuous cooling process of FGH95 superalloy

HE Feng, WANG Wu-xiang, YANG Wan-hong, ZOU Jin-wen, WANG Xu-qing, HAN Ya-fang

2000, 20(1): 22-26.

[Abstract](1540) [PDF 198KB](172)

Abstract:
The relationship between the gamma prime phase content and the temperature was studied,obtained the relation between the gamma prime size and the cooling rate for the continuous cooling of FGH95 superalloy and the kinetic precipitation regularity of gamma prime phase.The results show the precipitation of gamma prime phase was not controlled by diffusion,but by nucleation mode.At the same time,for the quenching of FGH95 superalloy,it needs high speed cooling rate only when the temperature is higher than 1000℃,and at the temperature of 1000℃ below,the gamma prime phase almost ceased to grow up.According to this principle,we select the qualifying quenching medium for the heat treatment of FGH95 superalloy turbine disk.

Structure and high temperature hot corrosion of palladium modified aluminide coatings on nickel-base superalloy

HE Da-xiong, GUAN Heng-rong, JIANG Xiao-xia, SUN Xiao-feng

2000, 20(1): 27-32.

[Abstract](1468) [PDF 956KB](242)

Abstract:
Pd-modified aluminide coatings on casting nickel-based superalloy M38 were developed by conventional pack aluminizing technology.Pd-20wt%Ni was predeposited before aluminizing.The structure of coatings was thoroughly analyzed.A major difference between Pt-and Pd-modified aluminide coatings resides in the fact that the Pd zone is single phased and the constitutive phase is-(PdX,Ni1-X)Al.The corrosion-resistance of Pd-Ni-Al coatings was more 3.5 times in Na2SO4 melt,and obviously better in Na2SO4+NaCl melt than conventional aluminide coating at 1173K.Pd-Ni-Al coatings behave at least as well as commercial Pt-Al coatings under the same testing conditions.The hot corrosion mechanism was preliminary discussed.

Statistical analysis of porosity variations in plasma sprayed Cr₃C₂-NiCr coatings

LI Jian-feng, ZHOU Xia-ming, DING Chuan-xian

2000, 20(1): 33-39.

[Abstract](1499) [PDF 295KB](441)

Abstract:
Statistical analysis of porosity variations in plasma sprayed Cr3C2-NiCr coatings was carried out and effects of gun translation speed and coating thickness on porosity of the coatings were investigated.It was found that the porosity variations in all the coatings,which were sprayed using different gun translation speeds and with different thickness,followed the Normal,Lognormal and Weibull distributions.Their variance coefficients were from 0.17 to 0.48,and Weibull moduli from 2.0 to 6.2.The confidence intervals of porosity means estimated basing on the three kinds of distributions were somewhat identical.The porosity values were statistically higher for coating samples with thickness less than 75μm and then decreased to a constant.Among the three kinds of gun translation speeds of 50,75 and 100m/min,the gun translation speed of 75m/min produced the coating with the lowest porosity.

Study on curing agents and technology of liquid crystalline epoxy with aromatic ester mesogen

CHEN Li-xin, WANG Ru-min, LAN Li-wen, QI Shu-hua

2000, 20(1): 40-45.

[Abstract](1441) [PDF 955KB](261)

Abstract:
Liquid crystalline epoxy resin is a kind of structural and functional material with good applied prospect because it combines the liquid order with cross network advantages.The effects of curing agents,such as DDM,DDBA,DDS and technology on properties of liquid crystalline epoxy resin have been studied.The microstructure have been observed by SEM.The results show that the comprehensive properties of PHBHQ/DDM are the best.

Development of advanced polymer composites

CHEN Xiang-bao

2000, 20(1): 46-54.

[Abstract](5511) [PDF 1173KB](2160)

Abstract:
The advanced polymer composites community has made great progress during the past thirty years.An assesment on the state of the art of the advanced polymer composites as well as their applications in aviation industrial is presented.The future development and research prospects of advanced polymer composites are discussed.

Review and prospect on developments of cast superalloys

CHEN Rong-zhang, WANG Luo-bao, LI Jian-hua

2000, 20(1): 55-61.

[Abstract](5212) [PDF 906KB](1520)

Abstract:
A review on the 20th century development history of casting superalloys is presented.Several main events,vacuum melting,directionally solidified and single crystal superalloy,alloy design,Ni3Al-based casting alloys,numerical simulation technique and fine grain casting are described.Furthermore,some prospects on the developments of cast superalloy in the 21th century are proposed.

2000 Vol. 20, No. 1