CALCULATION ON THE YIELD STRENGTH OF A PRECIPITATION STRENGTHENING Ni－BASE ALLOYS

ＣＡＬＣＵＬＡＴＩＯＮＯＮＴＨＥＹＩＥＬＤＳＴＲＥＮＧＴＨＯＦＡＰＲＥＣＩＰＩＴＡＴＩＯＮＳＴＲＥＮＧＴＨＥＮＩＮＧＮｉ－ＢＡＳＥＡＬＬＯＹＳＬｉＢｏ；ＷａｎｇＺｈｉｘｉｎｇ；ＹａｎｇＨｏｎｇｃａｉ（Ｐ．Ｏ．Ｂｏｘ３２６，ＮｏｒｔｈｅａｓｔｅｒｎＵｎ...     

面心立方和体心立方金属的各向同性屈服行为

应用TBH理论揭示了在Lequeu等提出的五维应力空间中,各向同性fcc和bcc金属的任意两个切应力构成的屈服轨迹近似地为由主应力构成的π平面的屈服轨迹的内切圆,在此基础上,提出了以HHH屈服函数为基础的,其参数由M_p和τ_c两个微观参数完全确定的解析屈服函数     

ISOTROPIC YIELD BEHAVIORS OF BCC AND FCC METALS

Isotropic yield surfaces of bcc and fec metals have been simulated with TBH theory.Using thefive-dimensional stress space proposed recently by Lequeu et al.,the yield subsurfaces on anytwo of the three shear stresses can be considered as the inscribed circles of their correspondingsubsurfaces on n plane.Based on this concept,Hershey,Hosford and Hill (HHH) yield func-tion has been transformed into the formula where the parameters are uniquely determined bytwo crystallographic factors:the mean Taylor factor in plane strain (M_p) and the criticalshear stress (τ_) on slip systems.     

金属亚稳态孔蚀行为的电化学研究

综述了国内外近期在亚稳态孔蚀行为的研究方法,亚稳态小孔形核、生长的统计规律 ,亚稳态蚀孔生长和再钝化过程的机制及控制因素,亚稳态蚀孔向稳定蚀孔转变的临界条件等方面的 研究进展,并对进一步的研究作出了展望。     

铜镍合金海水腐蚀的表面与界面特征研究

采用金相（ＯＭ）、俄歇（ＡＥＳ）、扫描电镜（ＳＥＭ）及透射电镜（ＴＥＭ）等技 术手段对实海暴露试样进行探测分析,揭示了表面膜缺陷（如碳膜）、晶界缺陷（晶界析出物）等加速该 合金腐蚀进程的试验现象和内在根据,特别指出影响该合金海水腐蚀产物膜稳定性的主要因素,分析了其中的沿晶扩散及应变诱生调峰分解与沿晶腐蚀、沿晶脆断的相互关系。     

RANGE PARAMETERS IN METALS AND ALLOYS

The formulae for calculating the electronic stopping power.for heavy ion implanting into metalare derived by using Wigner-Sietz radius r_s,equivalent charge,Fermi velocity and Ziegler'svalues of hydrogen electronic stopping power.Meanwhile the.formulae of electronic stoppingpower S_e(E)for alloys with boride or CsCl structure are also proposed.The calculated resultsare found as follows:these formulae are suitable only for mono-or bi-borides,but not forborides with more complex structure such as Cr_5B_3 or W_2B_5;the coefficient γ,of S_e(E)for al-loys with CsCI structure deviating from Bragg's S_e(E)is directly proportional to charge trans-fer in alloy.This means the larger the charge transfer is,the more stronger the metallic bondis.Hence the S_e(E)created by metallic bond in alloys will increase; there is a tendency for it toincrease with increasing separation of two components in alloy on either side of Cr group atsame periods,when the two components are in different periods,the tendency is more larger.     

TRANSMISSION ELECTRON MICROSCOPY OF PHASE TRANSFORMATION IN METALS AND ALLOYS

簡单地叙述电子穿透金属薄膜所产生的衍衬成象(选择衍射成象)和选择区域衍射的原理,以及它們在研究相变与晶体缺陷方面的应用。这种方法的优点:能够把显微观察(6—8埃)与晶体結构分析結合起来;能够将相变与晶体缺陷联系起来。这对于了解相变的生核与长大过程有重要的作用。 对于透射电子显微术在研究过飽和固溶体中的脫溶沉淀及馬氏体相变两方面的应用以及所取得的进展,进行了綜合性的介紹。在脫溶沉淀方面討論的項目有: (1) 空位促进G.P.区以很高的速率生成; (2) 位錯綫及层錯带是沉淀相优先生核的地点; (3) G.P.区与共格沉淀使基体产生显著畸变,非共格沉淀会在基体中产生大量位錯。 在馬氏体相变方面討論的項目有: (1) 层錯与六角密堆馬氏体; (2) 馬氏体的精細結构(孿晶,层錯)与切变过程; (3) 鋼中馬氏体的結构与分解。     

EFFECT OF CONCENTRATION AND TRANSITION METALS ON CRYSTALLIZATION OF Fe-BASED AMORPHOUS ALLOYS

本文概要地总结了我们近年观测过的若干Fe-B基和Fe-Co-B-Si基非晶态合金的晶化行为,主要是成分对晶化温度T_(cr)和晶化激活能△E的影响.合金样品是宽1-2mm,厚30—50μm的液淬带.用差值扫描量热计(DSC)获得:(1)Fe-(100-x)B_x系的T_(cr)和△E都在x=16时出现最大值;(2)在所观测的几个合金系中凡过渡元素总含量的变化能使每原子的平均外层电子数减少的,T_(cr)和△E就随着上升.并依据近年被承认的理论模型作了讨论.     

高强度变形铝合金断裂韧度各向异性的机理和预测

本文运用断裂力学的基本理论和结果,结合材料的物理开裂机制,定量分析较弱晶粒界面、裂纹扩展途径偏斜和沿晶分层三种因素对高强度变形铝合金断裂韧度各向异性的影响,预测结果与大量实验数据都比较接近,说明合金强烈的断裂韧度各向异性主要来自以上三种机制,并可根据实际断裂机理可以预估合金半成品的短横向断裂韧度值。     

MECHANISMS AND PREDICTION OF FRACTURE TOUGHNESS ANISOTROPY OF HIGH STRENGTH Al ALLOYS

Contributions of weak grain boundary,cracking path deflection and grain boundarydelamination to fracture toughness anisotropy of high strength Al alloys were evaluated basedupon approaches of fracture mechanics in conjunction with physical cracking mechanisms.The predicted results are close to those experimentally determined in the literature and in thiswork.The strong anisotropy of fracture toughness of high strength Al alloys is therefore attri-buted mainly to weak grain boundary cracking,cracking path deflection and grain boundarydetamination.With the methods of this work,short-transverse fracture toughness values ofsome semi-products can he estimated from in-plane toughness values and corresponding frac-ture characteristics when it is difficult to be determined experimentally.     

FRACTURE STRENGTH OF WC-Co ALLOYS

ＦＲＡＣＴＵＲＥＳＴＲＥＮＧＴＨＯＦＷＣＣｏＡＬＬＯＹＳ①ＣａｏＳｈｕｎｈｕａＰｏｗｄｅｒＭｅｔａｌｕｒｇｙＮａｔｉｏｎａｌＬａｂｏｒａｔｏｒｙ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｃｈａｎｇｓｈａ４１００８３ＡＢ...     

退火及置换元素对Fe-Cr-Al基合金阻尼性能及强度的影响

制备了Fe-13Cr-6Al（原子分数,%）及用2%的Mo、Mn和Nb分别置换Fe-13Cr-6Al中的Cr,用0.5%和1%的Cu分别置换Fe-13Cr-6Al中的Al共6种合金.测试了各合金的阻尼性能和强度,通过金相观察和内应力分析研究了退火温度、冷却方式及合金元素对这两种性能的影响.结果表明：随着退火温度的升高,Fe-Cr-Al基阻尼合金阻尼性能升高,强度降低;随炉缓冷合金的阻尼性能高于水淬合金的阻尼性能,而前者的强度低于后者;0.5%Cu置换Al降低了位错与溶质原子之间的交互作用,但是提高了合金原子与基体原子的弹性交互作用,使合金的阻尼性能和强度都得到了提高.     

微观组织对7075铝合金的屈服强度和抗应力腐蚀性能的影响

利用透射电子显微术研究了7075铝合金在T6,CgS3和T73状态的微观组织,并讨论了组织结构与强度和应力腐蚀抗力(SCR)的关系.结果表明,影响合金性能的主要因素是基体析出相(MPt)的密度、尺寸和类型,在CgS3状态,MPt主要为η′过渡相,其密度约5×10~(16)/cm~3,尺寸5—7nm,合金的强度和SCR综合性能较佳.作者认为这应归因于位错绕过η′粒子的几率增大.     

DEPENDENCE OF HYDROGEN CONTENT ON HYDRIDE STRUCTURE AND YIELD STRENGTH OF TITANIUM PLATE

在540和650℃,含氢60—80ppm的纯Ti板材的屈服强度σ_(0.2)出现降低,进一步增加氢含量,σ_(0.2)不再降低。在室温和540℃,氢含量低于50ppm时,应力-应变曲线上有明显上下屈服点;在650℃或氢含量高于50ppm,明显的上下屈服点消失。由此算得纯Ti中氢原子与位错之间的最大互作用能为0.47—0.53eV。 纯Ti中的氢化物均为片状和针状。在氢含量低于80ppm时,氢化物为体心四方结构TiH_2;高于80ppm,为fcc结构TiH_2。在氢含量低至15ppm的试样中也发现了体心四方结构TiH_2。     

W, Co, Ni对时效合金强度和韧性的影响

研究了Ｗ,Ｃｏ,Ｎｉ对时效合金强度和韧性的影响。结果表明：高Ｃｏ的ＦｅＷＣｏ合金有强的时效硬化能力,但其韧性较低。以Ｎｉ取代部分Ｃｏ之后,合金的韧性得到大的提高。ＦｅＷＣｏ合金的Ｃｏ量约２３％,Ｗ,Ｍｏ总量超过１８％时,硬度增加甚少,韧性损害较大,而ＦｅＷＣｏＮｉ的Ｃｏ当量达２３％,Ｗ,Ｍｏ总量达２４％时获得最佳的强度和韧性的配合。萃取化合物的Ｘ射线衍射（ＸＲＤ）分析表明,时效合金的主要金属间化合物是Ｆｅ３Ｗ２型,还有Ｆｅ７Ｗ６和Ｆｅ２Ｗ型化合物。淬火态、退火态萃取物的化学分析表明,时效合金中,Ｗ,Ｍｏ主要存在于化合物中,而Ｃｏ,Ｎｉ主要存在于固溶体中。时效硬化主要通过Ｗ,Ｍｏ金属间化合物的析出引起。而Ｃｏ,Ｎｉ主要通过影响析出相的数量、析出物形态及分布状态来影响时效硬化。     

SURFACE YIELD STRENGTH AND FATIGUE LIMIT FOR STEELS

The surface yield strength(σ_(ms))for various carbon steels was studied by means of X-raydiffraction method.The results showed that it is.far below the bulk yield strength,and is theresistance against plastic deformation in the surface layer.The smooth fatigue limit is associ-ated with crack initiation which is a result of accumulation of plastic deformation.Experimen-tal results showed the relation of smooth fatigue limit for 50% survival with σ_(ms)is σ_(ms)=0.81tO 1.02 σ_(-1)for different steels.The smooth fatigue limit of a medium carbon steel for 99.9%survival with σ_(ms)is σ_(ms)=0.98 tO 1.10 σ_(-1).It is less expensive and time consuming to measureσ_(ms)than σ_(-1).     

轻质高强NiTi形状记忆合金的制备及其超弹性行为

采用球形尿素颗粒预造孔工艺结合梯级粉末烧结方法制备出孔形规则、孔径大的轻质高强多孔NiTi形状记忆合金.通过控制造孔剂(尿素)的含量可有效调节多孔合金的孔隙特征,获得孔径均匀,孔形圆整和孔隙率可控的样品,其中孔径为296-732 um,孔隙率为31%-61.6%;尿素形状和尺寸对多孔合金的孔隙特征有决定性影响,具有几何形态遗传性;尿素对多孔NiTi合金的组成相影响很小,相变仍具有马氏体相变特征;合金具有优良的力学性能和稳定的线性超弹性.     

金属多晶体塑性变形几何分析及双相TiAl基合金的室温塑性

通过对金属多晶体塑性变形几何分析表明,塑性应变量一定时,扫过单位体积晶体的位错线长度与晶粒尺寸成反比,从理论上证明了单位面积晶界所发射的位错线长度与晶粒尺寸无关,而晶粒间协调变形时晶界凸起或凹陷的畸变量与晶粒尺寸成正比。     

钛合金/不锈钢管接头结合性能评价方法

研究了钛合金/不锈钢管接头结合性能的试验方法,借鉴复合板的拉剪强度试验方法,经过大量实验,做出适合评价大直径多层复合管的结合强度的试验方法.