A CALCULATION METHOD OF PLE/NPLE TRANSTION TEMPERATURE IN γ→α TRANSFORMATION OF Fe-C-Xi SYSTEMS

根据局部平衡模型,Fe-C-Xi合金系铁素体生长模式可以分为合金元素Xi扩散控制的再分配局域平衡模式(partition local equilibrium,PLE)和C元素扩散控制的不分配局部平衡模式(no partition local equilibrium,NPLE).在基本热力学模型的基础上,建立了简便计算Fe-C-Xi合金系PLE/NPLE转变温度的方法.代入合金原始成分,即可准确计算这一成分对应的PLE/NPLE转变温度.应用这一方法计算了多种Fe-C-Xi合金系的PLE/NPLE转变温度.     

Fe-Mn-Al-Cr系亚稳奥氏体区γ→ε转变温度M_(εs)与成分的关系

在Fe-Mn-Al-Cr系亚稳奥氏体区内,用膨胀法测定了40种合金的γ→ε-马氏体转变温度M_(es)。以多元线性回归方法处理实验结果,建立了M_(es)与合金成分关系的经验公式。经验公式中,1Wt-％的Al,C,Cr分别使Fe-Mn合金的M_(es)降低约51,339,8℃;这个结果与以前研究它们对Fe-Mn合金γ→ε-马氏体转变的影响和Ishida计算它们对Fe-Mn合金γ→ε相变驱动力的影响一致。根据γ→ε-马氏体转变的层错机制,简要讨论了Al,C和Cr对Fe-Mn合金M_(es)的影响。     

PHASE COMPOSITION AND TRANSFORMATION STRESS OF PRIMARY LAMELLAR STRUCTURE IN γ-TiAl-BASED DUPLEX ALLOY DURING ISOTHERMAL DECOMPOSITION

应用Ｘ射线衍射测定了过饱和α２单相的Ｔｉ－４５％Ａｌ合金在９５０℃等温分解过程中,初生片层形成时的γ相转变分数及２和γ相晶格参数的变化。结果表明,初生片层中α２和γ相晶格参数的变化,结果表明,初生片层中α２相是亚稳相,其成分可以由自由能成分曲线的亚稳态α２相与γ相自由能成分曲线公切线的切点稳定,该成分的确定对定量计算合金自由能及发生不连续粗化的转变驱动有十分重要的作用;     

FORMATION OF PRECIPITATED AUSTENITE IN 9%Ni STEEL AND ITS PERFORMANCE AT CRYOGENIC TEMPERATURE

The formation of precipitated austenite in 9% Ni steel exposed at the temperature of α+γ re-gion and its influence on impact tonghness at cryogenic temperature have been studied.Austenite-rich and ferrite-rich bands are formed during soaking because of the re-distribu-tion of elements of C,N and Ni.The former phase is enriched of Ni,Mn,C and N,while thelatter one is relatively pure.Part of the austenite formed at intermediate temperatures trans-forms into martensite when the steel is cooled down to room temperature.The complex struc-ture which consists of fine martensite and austenite exhibits a moderate strength and highenough cryogenic toughness.The austenite enriched of C,N and Ni is still stable at thecryogenic temperature.The tearing ridges on the impact fracture surface is densely occupiedby the precipitated austenite,elongated along the tearing direction.One of the importantcause of the excellent eryogenic properties is that the precipitated austenite absorbs theimpurities and thus purifies the matrix of the steel.     

FORMATION OF PRECIPITATED AUSTENITE IN 9％ Ni STEEL AND ITS FUNCTION AT CRYOGENIC TEMPERATURE

研究了9％Ni钢在两相区温度保温时沉淀奥氏体的析出过程及其对低温冲击韧性的影响。结果表明:在两相区保温由于C,N及Ni的重新分布,形成富Ni,Mn及C,N的奥氏体富集区及相对纯化的铁素体富集区,两者呈深浅相间的条带状组织。中温转变的奥氏体冷却到室温时部分转变成马氏体。这种第二代马氏体与奥氏体高度细化,并交织在一起形成复杂的组织。而奥氏体中高度富集C,N及Ni,它在极低温度下仍很稳定。低温冲击断口的撕裂岭都是沉淀奥氏体密集的,它们沿撕裂方向拉长。说明细碎的马氏体与奥氏体交织的组织既保持一定的强度也提高了低温韧性,这同回转奥氏体吸收杂质纯化基体密切相关。     

IN-SITU OBSERVATION OF NUCLEATION AND GROWTH OF HIGH-TEMPERATURE δ PHASE DURING AUSTENITE → FERRITE+LIQUID PHASE TRANSFORMATION IN AN AISI304 STAINLESS STEEL

利用共焦激光扫描显微镜原位观察AISI304不锈钢加热过程中高温占相的形核与生长．结果表明，130m-1400℃之间δ相在，γ晶界处优先析出，而δ相在γ晶粒内“爆炸”形成需在1410℃以上；δ相形成主要受控于Ni原子的扩散；提高升温速率有利于δ晶粒细化，促使δ／γ平界面失稳并出现二次枝晶．δ相析出时以非小平面为主，另可见少量的小平面δ晶体；随着相变进行，小平面状δ相呈现出边缘钝化、向非小平面转变的趋势．利用平直界面稳定临界扰动理论探讨了δ相生长界面失稳的机制，并从结晶动力学对δ相生长方式转变的原因进行了分析．     

EFFECT OF HETEROGENEOUS DISTRIBUTION OF C AND ALLOYING ELEMENTS ON γ/α′ TRANSFORMATION IN A Fe-Mn-Cr-C ALLOY

The heterogeneous distribution of C and metallic alloying elements as well as the phase com- position changes before and after cold deformation of an Fe-Mn-Cr-C alloy have been stu- died by the use of Mssbauer spectroscopy.The austenites without and with C and metallic alloying elements are found in the alloy in as-solid solution state.While the martensites with- out and with C and alloying elements may be induced by cold deformation.The transforma- tion from austenite to martensite in the alloy is confirmed via theoretical computation and ex- periments to be controlled by the number of covalent electron pairs forming covalent bond in austenitic crystal cell of the alloy.The formation of strong covalent bond between C and me- tallic elements can vigorously retard the γ/α' transformation.     

ROOM TEMPERATURE AND 750℃ ISOTHERMAL SECTIONS OF Ag-Pd-Gd TERNARY SYSTEM (Gd≤25 at.-％) PHASE DIAGRAM

采用X射线衍射和金相显微镜分析方法研究了含0—25at.-％Gd的Ag-Pd-Gd三元系,作出了该体系部分相图的750℃等温截面和室温截面。发现在该二截面上都分别存在三个单相区、三个两相区和一个三相区。     

INTERACTION BETWEEN Cu AND LIQUID Sn(II)——SEM OBSERVATION OF INTERMETALLIC GROWTH

The features of Cu_6Sn_5 growing slowly at lower temperature and growing rapidly up over350℃,and or Cu_3Sn growing at higher temperatures,bave been detailedly observedunder SEM.The increase of Pb content seems to inhibit sequentially the growth ofCu_6Sn_5 in Pb-Sn alloy.     

STUDY OF(α-γ_r) REVERSE TRANSFORMATION TEXTURE IN Fe-30Ni ALLOY BY USE OF ODF THEORY

研究了Ｆｅ－３０Ｎｉ合金冷轧板由马氏体到奥氏体（α－γｒ）逆相变过程中的织构变化。原始材料的组织状态为形变马氏体、淬火马氏体及残余奥氏体。经过在不同温度加热后,利用Ｘ射线衍射精确测量了马氏体及奥氏体的取向密度分布函数（ＯＤＦ）。结果表明,逆相变过程中奥氏体的织构变化可分为两个阶段：低温区,奥氏体织构逆变为原冷轧奥氏体织构,相变的进行可解释为具有强烈取向选择的剪切机制;高温区,相变的进行为定向长大机     

ROOM TEMPERATURE AND 750℃ ISOTHERMAL SECTION OF Ag-Pd-Gd(Gd≤25 AT.-%)PHASE DIAGRAM

The room temperature section and the 750℃ isothermal section of the Ag-Pd-Gd ternaryphase diagram containing 0—25 at.-% Gd are constructed by X—ray diffraction analysis andoptical microscopy.Each section consists of 3 single phase regions,3 bi-phase regions and Itri-phase region respectively.     

MICROSTRUCTURE OF INTERFACE BETWEEN Y-MODIFIED REACTIVE ION PLATED Ti(Y)N COATING AND SUBSTRATE STEEL A3

The fine rnicrostrueture of the Y-modified ion plated Ti(Y)N coating/substrate steel A3system has been examined by means of TEM and microdiffraction technique.It was revealedthat the interface consists of 3 sublayers,i.e.α-Fe+Y_6Fe_(23),Ti+Y+FeTi and Ti_2N+YN+Ti_xN_y.The thicknesses of them are about 200,50 and 120 nm respectively.The phases inthe transition area seem to have certain orientation relations.The mechanism of interfaceformation has also been discussed.     

ROOM TEMPERATURE AND 700℃ ISOTHERMAL SECTIONS OF Gd-Pd-Pt(Gd≤33 at. -％) PHASE DIAGRAM

采用X射线衍射和金相显微分析方法研究了Gd-Pd-Pt三元系中含0—33at。-％Gd的区域,测定了它的室温和700℃等温截面。在该二截面上都分别存在5个单相区(固溶体Pd(Pt)或Pt(Pd),GdPd_3,GdPd_2,GdPt_2和GdPt_5),7个二相区(Pd(Pt)+GdPd_3,Pd(Pt)+GdPt_?,GdPd_3+GdPd_2,GdPd_2+GdPt_2,GdPt_2+GdPd_3,GdPt_2+GdPt_5和GdPd_3+GdPt_5),3个三相区(Pd(Pt)+GdPt_5+GdPd_3,GdPt_5+GdPd_3+GdPt_2和GdPd_3+GdPd_2+GdPt_2)。未发现任何新的三元金属间化合物。