ON THE TENSILE MECHANICAL PROPERTY OF Si-Mn TRIP STEELS AT HIGH STRAIN RATE

二．互ntYO*llCtloliAs kn OWOWn,the beh yyiors of the strength and ductility of material under dynamic con－dltlon are obviously differs尬from those under static condition．几ensure the reft劝ility ofstructure under dynamic or impact loading It Is necessar     

LOCALIZED SUPERPLASTIC BEHAVIOUR INα-TITANIUM AT HIGH STRAIN RATE

The microstructure ofx-Ti/mild steel composite fabricated by using constant stand-off cladding technique was observed with optical microscopy, SEM and TEM analvses. Veryfine equiaxed grains (<0.1μm) with a low dislocation density were observed in the adiabatic shear bands (.4SB);this enables a thermomechanical response that may lead to a superPlastic de formation.     

PRECIPITATION OF TiC IN METASTABLE β-Ti ALLOY

In order to clarify that the IFP and the “Type 2”α phase are also arising from TiC,ametastable β-Ti alloy was selected for investigation in this work.The results showed that af-ter heating the alloy just below the α+β→β transus temperature and quenching,the TiC lay-er existed at the α/β interface.The morphology of TiC is similar to that of the IFP arisingfrom TiH_2 in the α-β two-phase alloys.The IFP TiC also provided an easy crack path orthe crack initiation sites.The fracture is also identical to that caused by IFP TiH_2.The arceddiffractions(characteristic of “Type 2”α)were found in the selected area diffraction pat-terns of some specimens which had been isothermally aged after solid solution treatment.Theparticles which bring on the arced diffractions may be TiC on the basis of structure and lat-tice parameter analysis,not the so called “Type 2”α phase.     

PRECIPITATION OF TiC IN METASTABLE β-Ti ALLOY

本文研究了Ti-3.84Al-6.2Mo-10.43V-1.85Fe合金中TiC的析出行为.当合金经低于α+β→β转变温度加热淬火之后,在α/β相界面上存在TiC膜,其形貌与α-β双相合金中TiH_2界面相类似.TiC界面相提供了裂纹易扩展途径和裂纹萌生点.断口也与TiH_2界面相引起的相似.经β固溶处理后再等温时效,在有些试样的电子衍射花样中观察到了弧形衍射(2α相的特征衍射).根据合金成分和点阵常数分析,产生弧形衍射的质点可能是TiC,而非所谓的2α相.     

EFFECTS OF TRACE Zr ON FATIGUE CRACK GROWTH RATE OF HIGH DAMPING Zn-Al ALLOY

ＥＦＦＥＣＴＳＯＦＴＲＡＣＥＺｒＯＮＦＡＴＩＧＵＥＣＲＡＣＫＧＲＯＷＴＨＲＡＴＥＯＦＨＩＧＨＤＡＭＰＩＮＧＺｎ－ＡｌＡＬＬＯＹ￥ＺｈｏｕＳｈａｎｃｈｕ；ＬｕｏＢｉｎｇｈｕｉ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅ...     

TEM OBSERVATION OF PHASE TRANSFORMATION IN 47121 β-Ti ALLOY

用透射电镜研究了Ti-4Al-7Mo-10V-2Fe-1Zr亚稳β-Ti合金中的相变规律。结果表明,淬火态存在无热ω相(ω_a)。低于500℃时效,发生β→B+ω_(iso)→β+α转变。在400℃以下,α相均匀长大,450—500℃时效,初期由等温ω相(ω_(iso))转变的α相不再是均匀长大,在原始β相晶界和晶内局部处发生选择性长大。高于550℃时效,发生β→β+α直接转变,在多数α相的片中有内挛晶。内孪晶的量随着时效时间延长或温度升高而减少,最终消失。伴随这一过程;在α相片的边缘产生台阶和错动。低温或商温转变的α相,其与β相的晶体学取向都符合Burgers关系。本工作仅在一只试样的选区衍射花样中有弧形衍射斑,这最可能是TiH_2析出的结果。     

EFFECT OF α-PHASE MORPHOLOGY ON STRENGTHENING AND FRACTURE BEHAVIOUR OF 47121 β-Ti ALLOY

用TEM,SEM,X射线衍射及拉伸试验等研究了47121β-Ti合金的拉伸性能与α相形貌及其断裂行为的关系。结果表明,低温时效由ω相转变成的弥散α相质点,随其体积分数增加,质点间共格应力场发生交叠,产生较强的内应力,在负荷作用下,导致宏观脆断,而微观断裂机制仍属于韧窝,因此可以把局部的内应力区认为是形成精细韧窝的核心。魏氏组织的α相具有强的加工硬化效应,位错切割α相是主要强化机制,但以孪生形变的α相片阻止位错切过。晶界两侧形成的无析出带,以及随后形成的羽毛状α相群,都使晶界区弱化,导致形成类似沿晶型断口。     

EFFECT OF STRAIN RATE(?) ON STRAIN HARDENING EXPONENT n OF SOME METALLIC MATERIALS

Fariabh strain rate tension tests for 4 metallic materials show that as the strain rate in creases the strain hardening exponent n decreases.The trend follows a two stage linear relation between n and lg(?).When (?)<(?)_(ep’)i.e.under quasi-statie loading,n can be consideredas a constant,but when(?)>(?)_(ep’),n decreases rapidlv till an ideal plastic state,n=0.Thecharacteri=ations and mechanisms of so fiening induced by high (?)are discussed.     

TENSILE DEFORMATION AND FRACTURE BEHAVIOR OF Ti_3Al-Nb ALLOY AT HIGH TEMPERATURE

ＴＥＮＳＩＬＥＤＥＦＯＲＭＡＴＩＯＮＡＮＤＦＲＡＣＴＵＲＥＢＥＨＡＶＩＯＲＯＦＴｉ３ＡｌＮｂＡＬＬＯＹＡＴＨＩＧＨＴＥＭＰＥＲＡＴＵＲＥ①ＷｕＹｉｎｇ，ＺｈｅｎＬｉａｎｇ，ＹａｎｇＤｅｚｈｕａｎｇＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎ...     

STRAIN RATE SENSITIVTTY OF POLYCRYSTALLINE AND SINGLE CRYSTAL NiAl

ＳＴＲＡＩＮＲＡＴＥＳＥＮＳＩＴＩＶＴＴＹＯＦＰＯＬＹＣＲＹＳＴＡＬＬＩＮＥＡＮＤＳＩＮＧＬＥＣＲＹＳＴＡＬＮｉＡｌＨＳＵＳｈｕｅｎ；ＹＡＮＧＳｙｃｈｅｒｎｇ；ＨＯＮＷｅｉｐｉｒｎ；ＷＡＮＧＣｈｉｅｎｙｉＬＥＥＴｓａｎｇｓｈｅａｕ（Ｃｈｕｎｇ－Ｓｈａ...     

DYNAMIC STRAIN AGING BEHAVIOR OF K40S ALLOY

The dynamic strain aging behavior during tensile tests of K40S alloy has been investigated in the temperature range of 25-1100℃ with the strain rate range from 10-4 to 10-3s-1. The results show that four different types of serration, identified as A, B, C and E type serration were observed in the temperature range of 300-600℃. The strain exponents for onset of the serrated flow were calculated as 1.21, 2.19 and 1.61, and the activation energies as 121, 40 and 67kJ/mol for E, B and C type serration respectively. The main mechanism for dynamic strain aging discussed in light of the strain exponent and the activation energy.     

MICROSTRUCTURE CHARACTERISTICS OF A HIGH DUCTILITY γ-TiAL ALLOY

研究了Ｔｉ－３３Ａ－３ＣＲ－０．５Ｍｏ合金经包套锻复合热机械处理后的显微组织与力学性能。结果表明，合金经１２５０℃，４ｈ及控制冷却的最终热处理，可获得以均匀细小等轴γ晶粒为主，含少量β２相和少量α２相的亚双态组织。由于晶粒细化和晶界结构２改善，该合金室位伸适性达到５．０７％。     

HIGH TEMPERATURE CORROSION OF PREOXIDIZED Ni-Al ALLOY IN CHLORINE

ＨＩＧＨＴＥＭＰＥＲＡＴＵＲＥＣＯＲＲＯＳＩＯＮＯＦＰＲＥＯＸＩＤＩＺＥＤＮｉ－ＡｌＡＬＬＯＹＩＮＣＨＬＯＲＩＮＥＨＩＧＨＴＥＭＰＥＲＡＴＵＲＥＣＯＲＲＯＳＩＯＮＯＦＰＲＥＯＸＩＤＩＺＥＤＮｉ－ＡｌＡＬＬＯＹＩＮＣＨＬＯＲＩＮＥ￥Ｔｕ，Ｊｉａｎｇｐｉ...     

CREEP BEHAVIORS OF Pt-RE ALLOYS AT HIGH TEMPERATURES

The creep behaviors of Pt-RE alloys have been studied at 1200℃ and 1400℃.The results show that asmall amount of RE elements improves the creep behaviors of platinum greatly.The creep behaviors of PtGd0.5,PtLa0.5 and PtLa0.3 Gd0.2,are best among all the alloys studied.As far as the creep behaviors are concerned,the traditional heat-resistance alloy PtGd10 can be replaced by PtGd0.5.Particularly,the properities of PtGd0.5are near to those of PtRb10.For most of the Pt-RE alloys,long-time,static,super high-temperature treatment inair is of no advantage to the creep rupture life.The mechanisms of the effects of rare-earths on high-temperaturecreep properties of platinum are discussed.     

THERMAL CONDUCTIVITY OF Al-Li ALLOY AT CRYOGENIC TEMPERATURES

ＴＨＥＲＭＡＬＣＯＮＤＵＣＴＩＶＩＴＹＯＦＡｌ－ＬｉＡＬＬＯＹＡＴＣＲＹＯＧＥＮＩＣＴＥＭＰＥＲＡＴＵＲＥＳ￥ＳｕｎＤｏｎｇｓｈｅｎｇ；ＬｉＦｅｎｇｚｈａｏ；ＳｈａｎｇＬｅｉ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅ...     

MECHANICAL PROPERTIES OF TiaSiC2 AT HIGH TEMPERATURE

Creep and stress relaxation behavior, the elastic modulus and fracture toughness of machinable Ti3SiC2 at various temperatures from 20 to 1250℃ were investigated by means of three-point bending tests. The experiments were performed respectively at: (i) fixed stress and changed temperatures, and (ii) fixed temperature and changed stresses. A creep resistance parameter that represents the probability of creep deformation in a given condition was defined as a function of both applied stress and the threshold stress, varying in a range from 0 to 1. Elastic modulus at high temperatures was measured through comparing relative slopes of loading curves in cyclic loading curve. The fracture toughness measured by SENB method showed a stable value in the range of 25-1000℃, but over 1000℃, it declined abruptly from ～6.7MPa.m^1/2 to～2.0MPa.m^1/2 at 1200℃.     

MICROSTRUCTURES OF A NOVEL HIGH STRENGTH AND WEAR-RESISTING ZINC ALLOY

ＭＩＣＲＯＳＴＲＵＣＴＵＲＥＳＯＦＡＮＯＶＥＬＨＩＧＨＳＴＲＥＮＧＴＨＡＮＤＷＥＡＲ－ＲＥＳＩＳＴＩＮＧＺＩＮＣＡＬＬＯＹＬｉＹｕａｎｙｕａｎ；ＸｉａＷｅｉ；ＮｇａｉＴｕｎｇｗａｉＬｅｏ；ＬｕｏＪｕｎｍｉｎｇ；ＺｈｅｎｇＬｉｎｇｙｉ（Ｄｅｐａｒｔｍｅ...     

ELECTRON DIFFRACTION ANALYSIS OF Ti_3Si-PHASE IN NEAR α-Ti ALLOY

<正> 在近α-Ti合金中加入适量的Si,能提高其高温强度。Si与Ti、Zr形成细小的硅化物相,分布于α相的内部和边界,起到强化作用。我们曾用电子衍射方法,对几种含Si的钛合金的弥散相进行分析。结果,除了(Ti,Zr)_5Si_3和Zr_5Si_3两种六方晶格的硅化物相外,许多含硅的钦合金也存在四方晶格的TiSi相。     

DETERMINATION OF STATES OF STRESS AND STRAIN AT POLE OF HYDRAULIC BULGE ORTHOTROPIC SHEET SAMPLE

ＤＥＴＥＲＭＩＮＡＴＩＯＮＯＦＳＴＡＴＥＳＯＦＳＴＲＥＳＳＡＮＤＳＴＲＡＩＮＡＴＰＯＬＥＯＦＨＹＤＲＡＵＬＩＣＢＵＬＧＥＯＲＴＨＯＴＲＯＰＩＣＳＨＥＥＴＳＡＭＰＬＥ￥Ｚｈｏｕ，Ｗｅｉｘｉａｎ；Ｚｈｏｕ，Ｘｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＡｅｒｏｎａｕｔ...     

PLASTIC DEFORMATION BEHAVIOR OF ELECTROFORMED COPPER LINER OF SHAPED CHARGE AT DIFFERENT STRAIN RATES

The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge, deformed at high strain rate (about 1×107s-1) and normal strain rate (4×10-4s-1). The crystallographic orientation distribution of grains in recovered slugs which had undergone high-strain-rate plastic deformation during explosive detonation was investigated by electron backscattering Kikuchi pattern technique. Cellular structures formed by tangled dislocations and sub-grain boundaries consisting of dislocation arrays were detected in the recovered slugs. Some twins and slip dislocations were observed in specimen deformed at normal strain rate. It was found that dynamic recovery and recrystallization take place during high-strain-rate deformation due to the temperature rising, whereas the conventional slip mechanism operates during deformation at normal strain rate.