航空材料学报

EFFECT OF CHEMISTRY MODIFICATIONS AND HEAT TREATMENTS ON THE MECHANICAL PROPERTIES OF DS MAR-M200 SUPERALLOY

Zheng Yunrong, Wang Yuping, Xie Jizhou, Pierre Caron, Tasadduq Khan

1989, 9(1): 1-9.

[Abstract](1538) [PDF 1871KB](217)

Abstract:
Hf and Zr can promote the formation of eutectic(γ+γ'), MC2, and Ni5M phases. In the alloy with equal atomic percent Zr and Hf, the solubility of Zr in eutectic γ'is lower than that of Hf, and Zr content in Ni5M is much higher thanHf. This distribution of Zr is beneficial to the formation of Ni5M and lowers the strengthening efficiency of Zr. A pretreatment of 1130℃/3hr efficiently eliminaets Ni5M and, as a consequence, increases the incipient melting temperature of the alloy. The precipitation treatment of 1100℃/4hr leads to cuboidal γ' precipitation of about 0.5μm size and causes the Hf-containing alloy to have a much higher creep strength than the Hf-free alloy in the temperature range of 760 to 1050℃. The Hf-containing alloy showed greater L CF(low cycle fatigue)life in comparison to the Hf-free alloy. A similar tendency was found when Zr was either partially or totally substituted for Hf. A higher rate of solidification facitlitates enhanced LCF life due to a finer structure and more perfect orientation. Surface slip analysis showed that intersection of two sets of slip in adjacent grans occurred in the Hf-free and Hf-containing alloys, but cracking at the columnar grain boundary easily took place in the Hf-free ally. The number of surface cracks of LCF specimens and their length per unit area are much higher in the Mar-M200 alloy. MC cracking preferentially oceurs at long rod-shaped carbides perpen-dicular to the stress axis, and then propagates through the interdendric region. The Hf-containing alloy cracks along the crystallogrphic planesby separation of slip bands.

THE PROPERTIES OF AIRCRAFT ORGANIC GLASSES AND THEIR TEMPERATURE RISE UNDER HIGH-ENERGY LIGHT SOURCE

Zhang Senlin, Qin Tieguang

1989, 9(1): 10-15.

[Abstract](1543) [PDF 373KB](236)

Abstract:
The ditermination has shown that YB-2, YB-4 and other aircraft organic glas s es have similar transmission ability in relation to monochromatic light with different wave length. This paper establishes a method for calculating reflection, absorption and transmisson abillty of aircraft organic glasses relating to high-energy light source and thus resolves the problem of calculating temperature rise of material(or structure)caused by composite light. Under high energy light exposure, aircraft organic glass has a temperture gradient from surface to iner which results in corresponding change in mechanical properties and certain heat stress of certain degree.

THE MICROSTRUCTURE AND STRENGTHTOUGHNESS OF ULTRA-HIGH STRENGTH STEELS

Zhong Bingwen, Zhao Zhenye

1989, 9(1): 16-22,15.

[Abstract](1557) [PDF 1403KB](198)

Abstract:
An observation of microstructure features in the quenched ultra high strength steel(300M)at different temperatures was made. The results show that the structure consists of lath martensite and bainite. Usually, there is four martensitic fields in an austenite grain. The orientation between A and two martensitic laths may follow different equivalent K-S relationship. The lower bainite in steel changes microstructure features and relative orientation of lath martensite in a packet and thus decreaes effective grain size or lath size. The strength and toughness of steel are improved.

THE INFLUENCE OF DEFECTS ON STRENGTH OF CARBON FIBRE

He Fu, Wang Rune

1989, 9(1): 23-30.

[Abstract](1485) [PDF 917KB](346)

Abstract:
Carbon fibre is known as a brittle material. Its surface and inner defects can be directly observed by SEM. Presence of these defects is not only the main factor controlling strength, but also the cause of scatter of strength values. Experiment indicates that the thinner the fibre diameter, the higher the strength; the shorter the gauge length or the more the density, the higher the strength too and vice versa. This work, using native carbon fibre, experimently proves that carbon fibre can be characterized by Weibull parameter m. The carbon fibre having high m value must be less brittle and more flexible.

DETERMINATION OF RESIDUAL STRESS CAUSED BY FORMING IN TRANSPARENT AIRPLANE CANOPIES——A GRAPHIC METHOD BY MEANS OF THE BIREFRINGENCE IN THE FIRST SLICE

Wang Ziming

1989, 9(1): 31-39,30.

[Abstract](1590) [PDF 644KB](278)

Abstract:
A graphic method based on principle of superposition and self-equilibrium of residual stress is used for cliscriminating the thermal stress fringe quantitatively from the frozen stress fringe in PMMA. The residual stress caused by forming can be calculated from the thermal stress fringe in transparent airplane canopi es according to the earlier work of the author. The method has been applied in engineering.

REPAIR WELDING OF LONG-TERM SERVICED INCOLOY 800H WELDMENTS

Shi Changjing, Sha Yunci

1989, 9(1): 40-46.

[Abstract](1547) [PDF 1184KB](183)

Abstract:
This paper investigated the cause of crack initiation which occured in INCOLOY 800H welded joints used in petrochemical plants after long-term service. Repair procedures for crack preventing were provided and put into practice during overhaul of plants in 1986. Satisfactory results were obtained and no cracks were found in welded joints by dye inspection after two years'operation.

THE CHANGING TENDENCY OF INTERNAL STRESS BETWEEN COATING AND SUBSTRATE AND ITS INFLUENTIAL FACTORS AT ELEVATED TEMPERATURE

Li Fengmei, Zhao Jiapei

1989, 9(1): 47-53.

[Abstract](1462) [PDF 437KB](237)

Abstract:
The aim of this work was to research the changing tendency of internal stress between coating and stainless steel for finding out the influence of the number of thermal shock and duration at elevated temperature on internal stress of coating. Result has indicated the influence of the number of thermal shock on internal stress was much more than the duration at elevated temperature, the magnitude of internal stress was proportional to the number of thermal shock and inverse proportional to duration. Reducing the number of thermal shock and increasing the duraton at elevated temperature was significant for the service life of coating.

THE EVALUATION OF THE STANDARD ANALYTICAL METHODS OF TITANIUM AND TITANIUM ALLOYS

Shi Yongqin, Zhang Kehshen

1989, 9(1): 54-58.

[Abstract](1494) [PDF 411KB](147)

Abstract:
The standerd analytical methods of titanium and titanium alloys formulated at home and abroad are discussed in respect of the technical charaeteristics and present condition. The technical brief, feature and advantage of the standard analytical methods of titanium and titanium alloys issued by Ministry of Aeronautical Industry are described in detail.

1989 Vol. 9, No. 1