ISSN 0412-1961
CN 21-1139/TG
Started in 1956

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    , Volume 15 Issue 2 Previous Issue    Next Issue
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    AN INVESTIGATION OF THE DIRECTIONAL SOLIDIFICATION OF A NICKEL-BASE SUPERALLOY
    Lin Dongliang;Lin Tung-liang;Yao Deliang Shanghai Jiaotong University
    Acta Metall Sin, 1979, 15 (2): 177-303. 
    Abstract   PDF (7075KB) ( 680 )
    The structure and properties of a directionally solidified high strength castnickel-base superalloy have been studied. Directional solidification significantly in-creased the resistance to thermal-fatigue and intermediate temperature rupture lifeas well as the ductility and the tensile strength and high temperature rupture lifeof the alloy. The improvement of rupture life at certain intermediate temperature(about 760℃) was found to be due to an extension of the secondary stage ofcreep, whereas at a high temperature (about 980℃) the same improvementcame from an extension of the tertiary stage. The absence of grain boundaries inthe transverse direction gave rise to better mechanical properties, in particular, the<100> preferred orientation of the columnar grains played an important part inthe increased strength at elevated temperatures. The secondary creep rate was lowered and the second creep stage extendedafter high temperature solution treatment. This was found to be due to the solu-tioning of the coarse γ' phase on heating and the subsequent reprecipitation of auniformly dispersed fine γ' particles in the cast alloy after cooling. In the above directionally solidified alloy, primary MC carbides seem to serveas the sites for creep and thermal-fatigue crack initiation. This rather suggests thatthe high temperature mechanical properties of the alloy may possibly be furtherimproved if its carbon content is lowered.
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    EFFECT OF CERTAIN ALLOYlNG ELEMENTS ON THE MECHANICAL PROPERTIES OF A WROUGHT NICKEL-IRON BASE SUPERALLOY
    Wang Yunshi;Wang Sukun;Zhang Shunnan;Zhao Yucai;Li Shijin
    Acta Metall Sin, 1979, 15 (2): 187-196. 
    Abstract   PDF (733KB) ( 620 )
    The effects of certain alloying elements such as titanium, aluminium, molyb-denum, carbon, boron, etc. on the tensile, impact and stress-rupture propertiesof a 42Ni-35Fe-13Cr superalloy have been investigated. Titanium or molybdenumincreased the 0.2% proof stress, the elongation, and the impact properties at roomtemperature as well as the stress-rupture life of the alloy at elevated temperatures.The presence of aluminium up to 0.3% accelerated the formation of γ'-Ni_3 (Ti, Al).Carbon and boron promoted the formation of fine grain size, with an optimumat 0.035% C and 0.010% B, where a maximum stress-rupture life of such analloy was obtained. The strengthening mechanism of the above alloying elementsand their optimum contents are discussed. It is emphasized that a close controllof the carbon and boron contents of the alloy and demand of high quality andcleanness of the ingot are particularly important.
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    THE EFFECT OF η-PHASE IN AN IRONNICKEL BASE SUPERALLOY
    Ge Yunlong;Zhang Yongchang;Hou Cuiping Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1979, 15 (2): 197-304. 
    Abstract   PDF (1423KB) ( 668 )
    The γ'-η transformation and the formation of the η-phase itself on the me-chanical properties and hot-workability of an iron-nickel base superalloy (Fe-42Ni-13Cr-6Mo-2.8Ti-0.3Al) has been studied. The formation of η-phase was promotedby increment of titanium content as well as by hot-working energy, and was re-tarded by the addition of aluminium, molybdenum and minute boron. when suchan alloy did contain certain amount of η-phase, its rupture strength and/or stress-rup-ture life were reduced although its ductility and hot-workability were increased.
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    AN INVESTIGATION OF THE OXIDATION AND HOT CORROSION OF A 3SNi-15Cr TYPE IRON-BASE ALLOY
    Guo Jianting Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1979, 15 (2): 203-305. 
    Abstract   PDF (1727KB) ( 536 )
    The oxidation behaviour of a 35Ni-15Cr type iron-base superalloy in air overthe temperature range of 700 to 1000℃ for period up to 200 hours has beenstudied. The results obeyed the conventional parabolic law from which the valuesof activation energy Q_(P1)=41 and Q_(P2)=46 kcal per mole were estimated. The dif-fusion of Cr ions in Cr_2O_3 was obviously the governing factor to oxidation rateand X-ray analysis indicated that the surface scale consisted mainly of Cr_2O_3 witha certain amount of (Cr,Fe)_2O_3, TiO_2 and NiCr_2O_4. The results were confirmedby electron probe, showing surface enrichment of Cr, Fe and Ti. The scale wasdense and tightly adhered to the surface of the oxidized specimen. If such an alloywas previously alumited, its oxidation-resisting and anti-corrosion properties weremarkedly improved and the scale, being enriched with Al, Cr and Ti, now con-sisted mainly of α-Al_2O_3 with minute Fe(Cr,Al)_2O_4 and TiO_2. With alumiting,the scale was more dense and more tightly adhered to surface than without alumiting.
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    THE BEHAVIOUR OF ALLOYING ELEMENTS IN MARINE LOW-ALLOY STEELS I. THE INFLUENCE OF ALLOYING ELEMENTS ON THE CORROSION POTENTIAL OF LOW-ALLOY STEELS IN ARTIFICIAL SEAWATER
    Joint Res. Gp. of Corrosion; Shanghai Institute of Iron and Steel Research & Changchun Institute of Applied Chemistry; Academia Sinica
    Acta Metall Sin, 1979, 15 (2): 215-226. 
    Abstract   PDF (863KB) ( 697 )
    The effect of alloying elements such as Cr, Mo, Ni, Cu, Si, Al, V and Nbon stable corrosion potentials of low-alloy steels in artificial sea water at 30℃with or without aerating has been studied by variance analysis. Under non-aerat-ing static conditions, Cr or Mo caused the corrosion potential of steel towards posi-tive direction. The effect of Ni and Cu was similar to Cr and Mo, although tosome extent differed with different factorial experimental specimens. Positive mov-ing was observed when Si content in the steel was about 1%, but it changed tonegative with Si<0.5%. The joint effect of two elements as Cr and Mo, Crand Al, Ni and Cu, Cr and Ni, Si and Cr, Si and Mo etc. was such that posi-tive moving was generally observed. Under conditions of violent blowing air, el-ements which very markedly shifted the corrosion potential to positive directionappeared to be Mo, Ni and Cu, and with Cr somewhat to lesser extent. The effectof Al upon corrosion potential was marked only in the simultaneous presence ofCr. But this was not the case with Si, and its effect was negligible irrespectiveof its content. It would appear that the mutual interaction of alloying elements,particlularly with such combinations as Cr and Ni and Mo, Cr and Ni and Cu, Siand Mo etc., produced greater effect on corrosion potentials in aerated than inunaerated conditions, but such a difference was not observed when V is substitut-ed by Nb. Cr-Al was a compound agent appropriated for shifting the corrosionpotential towards positive direction.
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    THE BEHAVIOUR OF ALLOYING ELEMENTS IN MARINE LOW-ALLOY STEELS Ⅱ. THE INFLUENCE OF ALLOYING ELEMENTS ON THE LOCALISED CORROSION PROPERTY OF LOW-ALLOY STEELS IN ARTIFICIAL SEAWATER
    Joint Res. Gp. of Corrosion; Shanghai Institute of Iron and Steel Research & Changchun Institute of Applied Chemistry; Academia Sinica
    Acta Metall Sin, 1979, 15 (2): 227-234. 
    Abstract   PDF (565KB) ( 455 )
    The effect of the alloying elements on localised corrosion properties of low-alloy steels has been studied by simulation of an occluded anode cell. Si or Alshowed very strong beneficial main-effect, and at the same time often exerted im-portant influence on the behaviour of other elements. In the latter respect, Si wasthe stronger of the two. The beneficial effect of Cr was marked when the Si con-tent was low (0.1-0.2%), and completely disappeared when Si was increased to0.8-1.0%. Cu behaved somewhat opposite to that of Cr. Mo promoted the benefi-cial effect of Si or Cr, although the main effect of itself alone was unbeneficial.The main effect of Ni is weak, however, it could match with Cu, Mo and Cr-Alto yield beneficial results. With regard to the two elements which were present insteel only in small amount, V was preferable to Nb.
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    APPLICATION OF ETCH-FIGURE METHOD FOR THE EXAMINATION OF SILICON-IRON
    Luo Yang;La Qichun Beijing Institute of Iron and Steel Research
    Acta Metall Sin, 1979, 15 (2): 235-308. 
    Abstract   PDF (6313KB) ( 672 )
    Certain improvements of the etch-figure method, suitable for such fine-grain-ed specimens as the matrix of primary recrystallization or the non-oriented siliconiron, are described. The determination of the geometrical parameters of the etch-figures by conventional metallographic microscope is also given. The usefulness ofthe etch-figure method is supported by many practical examples, e. g. determining themisorientation between the neighbouring grains, measuring the orientation and thetextures, analysing the fractures, examining the orientation effect of domain struc-tures, ascertaining the deformation extent of deformed grains as well as indicatingthe orientation relationships between the precipitants and its matrix, etc. Scanningelectron microscope is very helpful for detailed observation and exact measure-ments of the etch pits, because of its long depth of view.
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    AN INVESTIGATION OF MAGNETIC Ni-Fe-Mo AND Ni-Fe-Nb ALLOYS
    Xu Wenchong;Wang Junjian;Su Xiujin;Li Zhihua Beijing Institute of Iron and Steel Research
    Acta Metall Sin, 1979, 15 (2): 252-311. 
    Abstract   PDF (2458KB) ( 563 )
    An investigation of the structures of Ni-Fe-Mo and Ni-Fe-Nb alloys has beencarried out by means of TEM supplemented by electron diffraction and X-ray dif-fraction analysis. The results obtained have been correlated with magnetic proper-ties as follows: Both alloys showed modulated structures, in which the Ni-Fe-Nb alloy beingcoarser and more predominant. As the proportion of modulated structures increases,the hardness of the alloy also increases, but vice versa in the case of its mag-netic permeability. The introduction of solute atoms Mo and Nb would lower the degree of or-dering in Ni_3Fe alloy, but fortunately only certain degree of ordering was sufficientto yield conditions for high permeability. A preprecipitating phase possessing thefcc (ordered) Ni_3Nb (γ′) structure and being coherent with the matrix,was observ-ed in the Ni-Fe-Nb alloy. This phase appears to promote the formation of modu-lated structures and exert a strengthening effect on matrix.
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    AN INVESTIGATION OF QUASI-CLEAVAGE FRACTURE IN STEEL
    Liao Chienchu;Sun Fuyu;Lan Fenlan Beijing Institute of Iron and Steel Research
    Acta Metall Sin, 1979, 15 (2): 259-313. 
    Abstract   PDF (2436KB) ( 1204 )
    The quasi-cleavage fracture has been studied in conjunction with the stressstrain behaviour of steel specimens. Consideration of the results obtained on dif-ferent varieties of steel indicate that the quasi-cleavage fracture may be interpretedin terms of certain transition fracture mechanism as follows: Microcleavage cracks are nucleated at certain places of high tensile strss con-centration, subsequently each of them propagates along the cleavage plane in grainsalready deformed and finally they merge together by microplastic coalescence.According to the above conception, the interaction between the cleavage crack andthe plastic deformation may be regarded as the most important characteristics ofquasi-cleavage fractures. Using quantitative fractography, correlation between thefractographic features of specimens and the parameters of its certain mechanicalproperties may be established.
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    QUANTITATIVE PHASE ANALYSIS BY X-RAY WITHOUT ANY STANDARD IN TEXTURED MATERIALS
    Lin Shuzhi Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1979, 15 (2): 266-273. 
    Abstract   PDF (589KB) ( 644 )
    Formulae derived for X-ray quantitative phase analysis without any standardin the case of specimens with identical texture have been shown to be in completeagreement with those derived by Zevin for randomly oriented specimens. Thus,when it is practicable by some ways (for example, by certain heat treatments) tochange the composition of the alloy phases without altering the texture of thespecimen, the method of quantitative phase analysis for such a textured specimencan be taken as identical with that for randomly oriented specimens. In cases where the absorption coefficients of the phases in a specimen happento be large, corrections for microabsorption are necessary and such corrections aregiven in the present work. The method mentioned above has been applied to a cold-rolled Fe-25%Mnalloy as well as to certain compacting specimens of Mo-Cu powders with satisfac-tory results.
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    "SINGLE GRAIN" OSCILLATING CRYSTAL METHOD FOR ULTRAMICROANALYSIS BY X-RAY
    Wu Qixing;Qin Daoxiong Research Institute of Daye Steet Works
    Acta Metall Sin, 1979, 15 (2): 274-314. 
    Abstract   PDF (1581KB) ( 673 )
    X-ray identification of certain superfine grains weighing 0.003μg each hasbeen carried out by means of "single grain" oscillating crystal method in an ordi-nary Debye-Scherrer camera. The principle of this method, the measurement andthe calculation of the diffraction angles, the number of diffraction spots and theirrelative intensities in reference to the relevant ASTM cards are discussed in detail.Attempts have also been made to revealing the presence of certain rare earth inclu-sions by this method as well as to further verifying the proposed formula.
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    DETECTION OF THE INITIATION OF CRACK BY A. C. POTENTIAL METHOD
    Res. Gp. of Fracture Toughness; Institute of General Machinery Research
    Acta Metall Sin, 1979, 15 (2): 283-291. 
    Abstract   PDF (702KB) ( 458 )
    The principle and characteristics of the A. C. potential method for crack de-tection has been described. Various types of steel specimens including ferritic, fer-rite-pearlitic, martensitic or austenitic etc. have been examined by this method. At-tempts have been made to clarify the different patterns of potential curves associ-ated with the different steels, the relation between the peak values of potentialcurves and the initiation of cracking, and the relation between the increment ofpotential and the crack growth. Factors causing changes on the potential curvesare tentatively discussed.
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    CERTAIN CRITERION FOR THE FORMATION OF AMORPHOUS SOLIDS
    Zheng Zhaobo Dept.of Physics; University of Science and Technology of China
    Acta Metall Sin, 1979, 15 (2): 292-295. 
    Abstract   PDF (223KB) ( 547 )
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    AN EXPRESSION FOR CALCULATING CRACK EXTENSION
    Zhao Tingshi Central China Engineering Institute
    Acta Metall Sin, 1979, 15 (2): 296-298. 
    Abstract   PDF (181KB) ( 572 )
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