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

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    LATTICE CONSTANTS OF DISORDERED AND ORDERED PHASES IN Au-Cu SYSTEM
    XIE Youqing(Department of Materials Science and Engineering; Central South University of Technology; Changsha 410083)Correspondent:XIE Youqing; professor; Tel: (0731)8879287; Fax. (O731)8826136Manuscript received 1997-11-14; in revised form 1998-02-12
    Acta Metall Sin, 1998, 34 (12): 1233-1242. 
    Abstract   PDF (776KB) ( 996 )

    According to characteristic crystal theory of alloy phases, atomic state of acomponent is split into some characteristic atomic states in the solid solution. Lattice constantsof alloys may be obtained by characteristic lattice constaat additive law, characteristic atomicvolume additive law and characteristic atomic state additive law, but they are not equal in value.Nine lattice constant functions of disordered binary solid solutions are introduced. The functionssuitable for disordered An-Cu alloys and their components have been determined. Lattice constats of Au3Cu, AuCu, AuCu3 and relevant ordered alloys as a function of composition havebeen pradicated. Theoretical values are in good agreement with eXperimental values.

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    RELATIONSHIP BETWEEN PARTIAL AND AVERAGE ATOMIC VOLUMES OF COMPONENTS IN Cu-Ni ALLOYS
    XIE Youqing(Department of Materials Science and Engineering; Central South University of Technology; ChangSha 410083)CorrsPondent: XIE Youqing; pwtsson Tel: (O731)8879287; Fax: (0731)8826136Manuscript received 1997-12-1; in revised form 1998-0406
    Acta Metall Sin, 1998, 34 (12): 1243-1248. 
    Abstract   PDF (502KB) ( 651 )
    General equations of relationship between partial and average molar propertiesof alloy components and functions of partial molar properties in CC theory have been established.The differential equation and its constraining equation between partial and average molar proWerties and general Gibbs--Duhem formula have been derived. It has been proved that the partialmolar properties calculated from various combinative functions of average molar properties areequal, but in general the partial molar properties are not equal to the average molar propertiesof a given component. All equations and functions established in this paper have been provedto be correct by calculations of partial and average atomic volumes of components and averageatomic volumes of the solid solutions in the Cu-Ni system.
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    STM STUDY ON THE SURFACE RELIEF EFFECTS ASSOCIATED WITH WIDMANSTAT SAWTEETH
    BO Xiangzheng; XU Ning; FANG Hongsheng(Department of Materials Science and Engineering; Tsinghua University; Beijing 100084)Correspondent: BO Xiangzheng; Tel: (010)62782361; Fax: (010)62771160;E-mail. As -dms @m ailTsinghua. edu. cnManuscript received 1997-12-29; in revised form 1998-03-23
    Acta Metall Sin, 1998, 34 (12): 1249-1254. 
    Abstract   PDF (2374KB) ( 698 )
    Surface relief effects associated with the widmanstatten sawteeth in an Fe-0.37C(mass fraction,%) alloy were investigated by scanning tunneling microscopy (STM) for the firsttake. the relief of the widmanstatten sawteeth is made up of a group of platelets. The height ofthe relief is about 61-171 urn, which is lower than that of grain boundary allotriomorph fromwhich sawteeth devoloped. Configuration of face-to-face sympathetic nucleation was observed ingrain boundary allotriomorphs, and the maximum shape deformation of their reliefs is 0.39. Theformation of surface relief caused by sawteeth and allotriomorphs precipitation can be rationallyexplained by the ledgewise growth mechanism. Ledgewise groWth mechanlism is applied to explainqualitatively the formation of a tent-shaped, complex-shaped and single-tilt surface relief.
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    CYCLIC DEFORMATION BEHMIOR AND FATIGUE CRACK INITIATION IN COPPER BICRVSTALS
    HU Yunming;WANG Zhongguang(State Key Laboratory for Fatigue and Fracture of Materials; Institute of Metal Research; The Chinese Academyof Sciences; Shenyang 110015)Correspondent; HU Yunming; Tel: (024)23843531-55gg5; Fax: (024)23891s20Manuscript received 1997-12-17; in revised form 1998-01-30
    Acta Metall Sin, 1998, 34 (12): 1255-1260. 
    Abstract   PDF (2499KB) ( 623 )
    The fatigue cracking behavior and mechanisms in three types of [34] iso-axialcopper bicrystals have been studied by using scanning electron microscopy (SEM). One bicrystalcontains a grain boundary (GB) perpendicular to the loading direction and the two others containtilting GBs. The experimental results show that the intergranular fatigue cracking is the mainmode in the fatigue failure for the three types of copper bicrystals. However, the fatigue craCkingmechanisms are different for the perpendicular GB bicrystal and the tilting GB bicrystals. Theintergranular fatigue cracks are mainly formed by impingement of persistent slip bands againstthe GB in the perpendicular GB bicrystal. While the fatigue cracking initiation is predominatelydetermined by the stress concentration resulted from steps for the tilting GB bicrystal. The foregoing difference between the fatigue cracking initiation mechanisms in the two types of bicrystalsis closely related to the specimens geometry with respect to the primary slip systems.
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    DIRECTIONAL COARSENING OF THE γ'-PHASE DURING COMPRESSION CREEP OF A SINGLE CRVSTAL NICKEL-BASE SUPERALLOY
    (TIAN Sugui ; ZHOU Huihua; ZHANG Jinghua;YANG Hongcai;XU YOngboHU Zhuangqi(State Key Laboratory for Fatigue and Fracture of Materials; Institute of Metal ReSearch; The Chinese Academyof Sciences; Shenyang 110015)(Department of Materials Sciences and Engineering; Northeastern University; Shenyang 110006)(Department of Metal Materials Engineering; Shenyang Polytechnic University 110023)Correspondent:TIAN Sugui; associate professor; Tel: (o24)-25927399; Fax: (024)e3891s2oManuscript received 1997-12-23; in revised form 1998-03-16
    Acta Metall Sin, 1998, 34 (12): 1261-1266. 
    Abstract   PDF (2387KB) ( 667 )
    The microstructures of a single crystal nickel-base superalloy with [001] orientation at different creep stages of the constant loading compression were observed by meansof TEM and SEM. The results showed that the strip--like rafts were formed along the directionparallel to the stress axis in a mode of the side plane link in primary creep. The applied stressresulted in the decrease of coherent strain and energy of the 7i/7 interfaces parallel to the stressaxis The energy released was supposed to be the driving force for the diffusion elements. Bycompared compressive creep with tensile, the longer time and bigger stress were needed for ther' rafted.
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    CELLULAR SPACING SELECTION OF Al-0.53Zn ALLOY UNDER NEAR-RAPID DIRECTIONAL SOLIDIFICATION CONDITION
    FENG Jian; HUANG Weidong; LIN Xin; LI Tao; XUE Yeing; ZHOU Yaohe(State Key Laboratory of Solidification Processing; Northwestern Polytechnical University; Xi'an 710072)Correspondent:FENG Jian; Tel: (O29)-8494001; Fax: (0E9)-8491544;E-mail. Huang@nwpu.edu.cn Manuscript received 1998-03-10; in revised form 1998-06-01
    Acta Metall Sin, 1998, 34 (12): 1267-1272. 
    Abstract   PDF (2252KB) ( 550 )
    In order to investigate the response of primary cellular/dendritic spacing selection to the variation of growth velocity under near-rapid directional solidification condition, anAl-0.53Zn alloy is directionally solidified with Bridgman apparatus. The results show that atthe given temperature gradient the microstructures is cells and there exists a wide distributionrange of cellular spacing. The maximum, A..., minimum, and average cellular spacing,A, as fullctions of growth rate, v, can be given by λmax=948.51v(-0.4961),λmin=661.16 v(-0.5015),λ=412.41 v(-0.5049), respectively. The experimental results are compared with that predicted bythe current KGT model, and a good agreement is found. Moreover, it is found that the averagecellular spacing is also remarkably history-dependent.
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    ON CHARACTERIZATION OF MICROSTRESS MEASURED BY X-RM DIFFRACTION
    ZHANG Dingquan(Shaoxing College of Arts and Sciences; Shaoxing 312000)HE Jiawen(State Key Laboratory for Mechanical Behavior of Materials; Xi'an Jiaotong University; Xi'an 710049)Correspondent:ZHANG Dingquan; associate professor;Tel: (O575)8067050-2812; Fax. (0575)8067917;E-mail: ZX9915@163.NetManuscript received 1998-02-09; in revised form 1998-07-10
    Acta Metall Sin, 1998, 34 (12): 1273-1278. 
    Abstract   PDF (558KB) ( 1136 )
    Microstress measured by X-ray diffraction method is usually characterized bypeak profile. When the classification of internal stress is based on the model suggested by Macherauch, the second kind of internal stress in the crystalline should be associated with the statisticdeviation of strains in various grains with respect to macro-strain.The value of macro-strainleads to the evaluation of the first kind of internal stress. However, in some cases micro-strainalso results in the peak shift of X-ray diffraction profile. Therefore, besides of peak broadening,one should keep an eye on the effect of dricro-strain on peak shift when microstress is evaluated.The peak shift part stands for the average value and the peak broadening stands for its deviation.
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    INTERFACIAL CHARACTER OF PRIMARY α_2/γLAMELLAE FOR γ-TiAl-BASED(α_2+γ) TWO-PHASE AllOY
    QIN Gaowu; HAO Shiming(School of Material & Metallurgy; Northeastern University; Shenyang 110006)SONG DanMaterials Test Center; Northeastern University; Shenyang 110006)Correspondent:QIN Gaowu; Tel: (oB4)-2389000- : (o4)23906316;E-mail: gwqin@mail neu.edu cnManuscript received 1997-12-16; in revised form 1998-04-02
    Acta Metall Sin, 1998, 34 (12): 1279-1283. 
    Abstract   PDF (1641KB) ( 594 )
    The interfacial character and formation of primary α2/γ lamellae in the or orsupersaturated α2 matrix for γ-TiAl-based (α2+γ) two-phase alloy were investigated by opticalmicroscopy and TEM. The formation of primary α2/γ lamellae is through either α-α2γorα- α+γ -α2+γ transformation. Theγ lamella nucleates at grain boundary and growsthrough the ledge mechanism controlled by volume diffusion process. The growth velocity of 7lamellae along the longitudinal direction in the matriX is about (1.0 - 3.33) x 10(-7) m/s. Theprimary or2/7 interface was determined to be sendcoherent, and the α2/γ interfacial energy wasestimated to be about 0.274 J/m2.
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    MICROSTRUCTURAL CHARACTERISTICS AND WEAR PROPERLIES OF IN SITU FORMED TiC PARTICLE REINFORCED COATINGS BY LASER CLADDING
    WU Xiaolei; CHEN Guangnan(Institute of Mechanics; The Chinese Academy of Sciences; Beijing 100080)Correspondent: WU Xiaolei; postdoctor Tel: 6B547527; Fax: 6B561284;E-mail: xlwu@ccs5.imech. ac. cnManuscript received 1998-03-05
    Acta Metall Sin, 1998, 34 (12): 1284-1288. 
    Abstract   PDF (2963KB) ( 708 )
    A new method was realized to produce a Ni-alloy composite coating reinforcedby in situ reacted and gradiently distributed TiC particles (TiCp) by one step laser cladding.TiCp was introduced by an in situ reaction of titanium and graphite during laser clad process.It was observed that the disperse TiCp with size of sub-micrometer formed in the layer. And,TiC. possessed density--gradient distribution and a maximum volume fraction of 38% at thelayer surface. Furthermore, the in situ generated TiCp/matrir interfaCes is found to keep cleanand free from deleterious surface reactions. The microhardness revealed a gradient variationwith the layer depth,and the highest value was 1250 HV0.2. The wear properties of the layeris significantly enhanced due to a large amount of TiCp and strong phase interface combinationwithout evidently increasing the friction coefficient.
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    MICROSTRUCTURES AND PROPERTIES OF DZ40M Co-BASE SUPERALLOY AFTER LONG-TERM AGEING AT 950℃
    JIANG Wenhuil; YAO Xiangdong; GUAN Hengrong;HU Zhuangqi(Institute of Metal research; The Chinese Academy of Sciences; Shenyang 11O015)(Shenyang Polytechnic University; Shenyang 110023)Correspondent:JIANG Wenhui; Tel: (0U)2384353l-556o8; Fax: (024)23891320Manuscript received 1997-12-16; in revised form 1998-03-10
    Acta Metall Sin, 1998, 34 (12): 1289-1294. 
    Abstract   PDF (2768KB) ( 798 )
    DZ40M, a newly developed directionally solidified Co-base superalloy was agedat 950℃ for long term. Its microstructural charateristics and mechanical properties at roomand elevated temperatures were studied. Long-term ageing results in substantial increase intensile strength and sharp reduction in ductility at room temperature. Its effect oil mechanicalprOPerties at elevated temperatures is dependent on eXperimental parameters. At 980℃ , 83 MPa,stress-rupture life is prolonged and at 816 ℃, 215 MPa, it is shortened. However, in all of thecases, the alloy possesses a high stress-rupture ductility. During ageing, primary carbide M7C3and MC decomposed sluggishly, fine M23C6 precipitated copiously around them and M6C formedon the surfaCe of some M7C3. Decomposition of the primary carbides promoted the precipitationof M23C6 by supplying carbon atoms and segregation of tungsten caused the precipitation ofM6C. It is thought that the change of mechanical properties of the alloy is attributed to theM23C6 precipitation.
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