固溶处理温度对7A85航空铝合金微观组织及力学性能的影响

运用光学显微镜、扫描电镜和透射电镜研究了固溶处理温度对7A85铝合金微观组织和力学性能的影响。试验结果表明:随固溶温度的提高,7A85铝合金的屈服强度、抗拉强度和断裂韧性均先增大后减小,450℃时达到峰值,分别为624 MPa、679 MPa和38 MPa·m~(1/2);随固溶温度的升高,基体再结晶晶粒的尺寸增大,晶粒的均匀性相对提高,粗大第二相粒子含量降低,人工时效过程获得更多弥散析出的纳米强化相粒子;不同固溶处理后的断裂方式均为穿晶断裂和沿晶断裂的混合断裂机制,固溶温度越高,弥散韧窝越多。     

Ti3Al基合金的拉伸形变和断裂

测试了三种显微组织Ｔｉ３Ａｌ基合金的室、高温拉伸性能；并用ＳＥＭ和ＴＥＭ详细观察样品的形变和断裂特征，结果发现，材料的力学性能与断口和位错组态的变化密切相关，随实验温度升高，强度降低，延性增加；随固溶温度提高，强度增加，延性降低，三种组织室温拉伸均为解理断裂，温度呈现解理与沿晶混合断裂。     

Ti-38644合金中硅化物的溶解析出及对力学性能的影响

研究了Ti-38644合金中硅化物的溶解和析出行为及其对室温拉伸性能的影响,并利用扫描电镜和透射电镜对显微组织、析出相及拉伸断口进行了观察和分析。结果表明,合金中的杂质Si导致(TiZr)_6Si_3硅化物的形成。在700~950℃之间固溶1 h后,合金中的硅化物随固溶温度升高逐渐溶解,而950℃固溶样品中未观察到硅化物。由于硅化物的溶解和β晶粒长大,800~950℃之间固溶后的合金强度随固溶温度升高而降低。合金经1100℃固溶1 h,再经750~900℃时效1 h后,硅化物在晶界处析出,而在700℃和950℃时效1 h的样品中未见硅化物的析出。800~950℃之间时效后的合金强度基本不变,晶界硅化物对合金抗拉强度影响不大,但合金塑性随晶界硅化物含量减少而提高,断裂模式由脆性断裂转变为韧性断裂。     

AuAgCu合金组织与性能研究

采用真空熔炼、轧制和固溶处理,然后冷加工75%制备Au Ag Cu35-5合金片材。研究合金固溶和时效处理对组织和力学性能的影响。结果表明:500℃固溶处理时,合金组织为纤维状回复再结晶结构。随固溶温度增加,组织发生完全再结晶并长大,形成贯穿晶粒的完整退火孪晶。炉冷和时效处理时,组织为等轴细小的球形晶粒。合金的硬度随固溶温度升高而降低,时效硬度随温度升高而增大。300℃时效时,硬度在3 h时效时达到峰值,然后随时间增加,缓慢降低。     

热处理工艺对Ti-3Al-6Mo-2Fe-2Zr合金组织和性能的影响

采用OM、SEM和XRD等方法研究了固溶时效热处理对近β型钛合金(Ti-3Al-6Mo-2Fe-Zr)显微组织、力学性能及耐腐蚀性能的影响。结果表明,随着固溶温度的升高,初生α相的含量逐渐降低,经930 ℃固溶处理后,合金为单一β相。固溶温度在830 ℃以下时,随着固溶温度的升高,初生α相逐渐转变为β相,第二相强化作用减弱,合金强度逐渐降低,塑性逐渐提高,断裂方式为微孔聚集型;固溶温度在830 ℃以上时,随着固溶温度的升高,β相晶粒逐渐粗化,合金强度降低,塑性下降,断裂方式由微孔聚集型断裂向解理断裂转变。随着固溶温度从780 ℃升高至930 ℃,初生α相的含量降低,β/α相界逐渐减少,耐腐蚀性能提升。经780 ℃固溶1 h(水冷),500 ℃ 时效6 h(随炉冷却)处理后,细小针状的次生α相于亚稳β相中沉淀析出,合金强度显著提高,但塑性下降。     

固溶-时效热处理工艺对近β钛合金显微组织演化与力学性能的影响（英文）

研究钛合金Ti-5Al-5Mo-5V-3Cr-1Zr(Ti-55531)在不同固溶(760～820℃)与时效(580～640℃)热处理条件下的显微组织演化、力学性能及断裂机理。结果表明,初生α相(α_p)的体积分数随固溶温度的升高而降低,而次生α相(α_s)的长度随时效温度升高而降低,其宽度则随时效温度升高而增加。Ti-55531合金的屈服强度和抗拉强度随固溶温度升高而降低,但随时效温度的升高而增大。合金在800℃固溶2 h、640℃时效8 h的条件下获得的抗拉强度(1434 MPa)与韧性(伸长率7.7%)达到最优匹配。随时效温度和时间的增加,α_s相发生粗化,使微观裂纹扩展路径变得曲折、崎岖,从而提高裂纹扩展阻力,最终提高合金的韧性与断裂韧性。     

固溶温度对超纯净18Ni(350)马氏体时效钢断裂韧性及微观组织的影响

研究了在1083—1483K温度范围内，固溶温度对超纯净18Ni(350)马氏体时效钢断裂韧性(KIC)的影响．通过透射电镜(TEM)研究了马氏体时效钢微观组织的变化，结合相变曲线和断口扫描电镜(SEM)观察，探讨了固溶温度对断裂韧性的影响机理．结果表明：超纯净马氏体时效钢的断裂韧性(KIC)随着固溶温度的升高或再结晶晶粒尺寸的长大而增加，不存在常见的Ti(C，N)在晶界偏聚而引起的“热脆”现象．固溶态马氏体时效钢由单一的马氏体板条组成，其形貌、间距以及位错密度不受固溶温度的影响．在时效过程中，随着固溶温度的升高或再结晶晶粒的粗化，Ni3(Mo，Ti)等时效析出相在晶界或板条界的偏聚程度逐渐加重并导致基体软化，合金元素Ni，Mo的富集诱发了逆转变奥氏体形成．这使裂纹尖端易于钝化而表现出韧窝状穿晶断裂和保持较高的断裂韧性．     

纳米多晶Cu-Ni合金三轴拉伸变形模拟

采用分子动力学对纳米多晶Cu-Ni合金三轴拉伸性能进行了模拟研究，从微观尺度探究了Ni含量及温度对合金拉伸性能的影响规律。结果表明，当Ni含量为10%时，最大拉应力达21.70 GPa,位错之间的相互作用是造成拉伸性能提升的重要原因。从能量、位错和堆垛层错方面对Ni含量为10%合金的性能进行了验证，表明Cu-Ni合金符合固溶弱化规律。当温度为100 K时，存在最大拉应力为22.21 GPa;当温度为900 K时，最大拉应变为0.1045。晶界原子百分比随加载温度的升高而增加，晶内原子百分比随加载温度的升高而减少；温度升高导致晶界熔化，原子无序度增加，对位错的阻碍作用下降。拉伸过程中位错密度不断降低，由位错缠结而引起的强化作用不断减少，导致高温时合金的拉伸性能下降。     

热处理工艺对GH4151合金冲击性能的影响

采用冲击实验研究了不同温度固溶处理及固溶和双级时效处理对GH4151合金冲击性能的影响，采用光学显微镜、扫描电镜和透射电镜等观察了合金经不同工艺处理后的显微组织、析出相和断口形貌。结果表明：对于仅固溶处理的合金，当固溶温度低于1140℃时，其冲击韧性值的变化不大，固溶温度高于1140℃时，冲击韧性值随固溶温度的升高而增加，断裂过程以裂纹的稳定扩展区为主，断口呈韧性断裂。对于固溶时效处理的合金，当固溶温度低于1160℃时，冲击韧性值的变化也比较稳定，固溶温度高于1160℃时，冲击韧性值随固溶温度的升高而降低，断裂过程不存在裂纹的稳定扩展区，断口呈典型的沿晶脆性断裂。这主要是因为当固溶温度低于1140℃时，合金的晶粒尺寸变化不大，而在1140℃以上时晶粒尺寸明显增大；双级时效后，当固溶温度高于1160℃时，晶界上连续或不连续分布的第二相显著降低了合金的冲击韧性。     

固溶时效对高铝青铜组织与性能的影响

采用光学显微镜、扫描电镜、X射线衍射分析和力学性能测试等方法研究了固溶时效对高铝青铜组织与性能的影响.试验结果表明,该高铝青铜随固溶温度升高,晶粒长大,K相和γ2相大量溶解;随时效温度的升高,强化相由部分析出到完全析出,甚至发生共析反应,导致力学性能降低.高铝青铜进行950℃×2h固溶和500℃×5h时效可获得高强韧性β相中均匀分布K相和γ2相的组织,因此该材料在该固溶时效条件下具有较高的综合力学性能.     

CRYOGENIC MECHANICAL BEHAVIOUR OF MARAGING STEEL CONTAINING HYDROGEN

Within the range of 77 to 295 K,the strength and plastieity of 18Ni maraging steel increasewith decreasing temperature and decrease with increasing hydrogen content.The susceptibilityto hydrogen embrittlement of the maraged specimens is superior to solid solution ones.Thedislocations after plastically deforming will tangle into dislocation cells which reducethermselves in size as the temperature decreases,and coarsen as the hydrogen content in-creases.No cryogenie deformation twin was found.The tensile fracture surfaces of the solu-tion and maraged specimens containing 5.90 ppm hydrogen under 295 to 223 K are revealedas quasi-cleavage and intergranular features respectively and as transgranular ones underother experimental conditions.The influence of hydrogen on the mechanical behaviour ofsteel and the mechanism of hydrogen induced deformation and fracture are discussed. Research Assistant,Institute of Metal Research,Academia Sinica,Shenyang 110015,China     

一种Al-Li-Zn-Zr合金在室温与低温下的反常拉伸断裂行为SCIEI

本文研究了一种Al-Li-Zn-Zr合金从室温到77K范围内的拉伸性能与断裂行为,结果表明,随实验温度的降低,合金的拉伸极限强度与延伸率均提高,屈服强度基本不变;合金在室温时为明显的穿晶断裂,而77K则主要为沿晶断裂形式;断口附近室温及低温下的变形模式基本相同,但室温时断裂主要与平面滑移有关,而低温时平面滑移倾向大大减弱,此时合金的断裂与位错和晶界的交互作用有关。     

温度对SAF2205双相不锈钢组织与性能的影响

采用慢速拉伸的方法研究了SAF2205双相(α γ)钢在293～77K温度范围内的拉伸性能与组织变化。结果表明:随着试验温度的降低,该钢的强度明显增加,面缩率则呈相反趋势,而延伸率在153K时达到极大值后随温度降低而减小;降低温度及变形能够促进马氏体转变。     

Experimental investigation of plastic deformation of stainless steel for cyclic loading at low temperature

Cyclic plastic deformation of stainless steel SUS 304 is experimentally investigated at low temperature of liquid nitrogen (77 K) under various cyclic loading conditions Thin walled tubular specimens are subjected to cyclic loading under constant strain ranges. At low temperature, the material shows remarkable hardening by cyclic loading comparing with cyclic loading at room temperature. The hysteresis curves of stress-strain relations by cyclic loading are saturated by increasing the cycle numbers. The saturation tendency depends on loading direction. The saturated stress values are related with cumulative plastic strain of cyclic loading. The prestraining is given at 77 K by axial and torsional loadings, and subsequent cyclic loading under constant strain range is conducted at 77 K. The cyclic stress-strain curves are saturated by increasing cyclic numbers. At small cyclic numbers, cyclic plastic deformation depends on the prestrain direction. The directional effect of pre-strain on cyclic loading becomes small with increasing number of cycles.     

In-situ neutron diffraction analysis on deformation behavior of duplex high Mn steel containing austenite and ?-martensite

The deformation behavior of Fe-17Mn-0.02C steel containing ?-martensite within austenite matrix has been investigated via in-situ neutron diffraction study at 298 K and 77 K. Based on the analyses of changes in phase fraction and lattice strain, it has been shown that the steel shows the deformation-induced phase transformation of austenite ?? ?-martensite ?? ????-martensite and the direct transformation of austenite ?? ????-martensite at both temperatures. However, the kinetics of such transformations vary with temperature, resulting in a higher and more persistent work hardening at 77 K than at 298 K.     

时效对JN1奥氏体钢超低温断裂韧度的影响

ＪＮ１ 奥氏体钢１３４８Ｋ固溶处理与９２３ 、９７３ 、１０７３Ｋ 时效５ｈ 后,４Ｋ 及７７Ｋ 断裂韧度测定结果表明,该钢有明显的时效脆化倾向。组织观察及Ｘ 射线衍射结果确认,时效脆化是Ｍ２３Ｃ６ 型碳化物沿晶界及退火孪晶界析出造成的。     

Corrosion behavior of titanium-clad carbon steel in weakly alkaline solutions

The electrochemical polarization curves and corrosion potentials during long-term immersion of Ti, carbon steel, carbon steel tightened-Ti and Ti-clad carbon steel specimens were investigated in bentonite-contacting solution (mixture of sodium sulfate and sodium carbonate solutions), sodium sulfate solution and borate solution adjusted to pH=9.0-9.84. Ti and carbon steel were passivated during immersion in borate solution, while carbon steel was corroded in the solutions containing SO₄²⁻ ions. The immersion potentials of Ti-clad steel and steel-tightened Ti specimens were controlled by the corrosion potential of carbon steel (about 0 V vs. RHE at 298 K). The Ti side of the clad specimen was, therefore, polarized cathodically at this immersion potential, and this caused hydration of and/or hydrogen penetration into the oxide film, resulting in degradation of its barrier property. Furthermore, the cathodic current on the Ti side was partially coupled with the anodic current in the corrosion reaction on the carbon steel side, resulting in acceleration of the overall corrosion rate.     

Effects of potential, temperature and pH on hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy in 0.9% NaCl solution

The effects of electrochemical potential, solution temperature and pH on the hydrogen absorption and desorption behaviors of Ni-Ti superelastic alloy immersed in 0.9% NaCl solution for 2 h have been investigated systematically by hydrogen thermal desorption analysis. For hydrogen cathodic charging under constant applied potential, upon increasing solution temperature, the critical potential for the hydrogen absorption very slightly shifts to a noble direction. As solution pH decreases, the critical potential for the hydrogen absorption shifts markedly to a noble direction and approaches to the corrosion potential; the critical current density for the hydrogen absorption slightly decreases. At a less noble potential than the critical potential for the hydrogen absorption, the amount of absorbed hydrogen increases markedly with decreasing applied potential. For hydrogen cathodic charging under constant current density, the amount of absorbed hydrogen increases with increasing solution temperature and decreasing solution pH. The basic hydrogen desorption behavior only slightly depends on solution temperature or pH. Nevertheless, hydrogen desorption at low temperatures for specimens subjected to cathodic charging under constant current density is observed distinctly as compared with that under constant applied potential.     

3种高强铝合金的低温拉伸力学性能研究

利用拉伸测试、扫描电镜与透射电镜等手段,研究了2519-T87、2219-T81以及7039-T6三种铝合金板材的拉伸力学性能.结果表明,当变形温度由室温293 K降至77 K时,3种合金的屈服强度与抗拉强度均有所提高,其中抗拉强度分别提高23.1%、12.0%及6.2%.同时3种合金的伸长率随着温度降低有所提高.由于低温变形过程中平面滑移受抑制,加工硬化指数增加,变形均匀性增强,导致材料的强度增加,塑性有所提高.     

High temperature deformation behavior of spray-formed and subsequently extruded Al-25Si based alloy

The high temperature deformation behavior of spray-formed and subsequently extruded Al-25Si based alloy containing fine Si and ultra-fine intermetallic phases was examined by compressive tests at temperatures between 523 and 743 K and strain rates between 1.0 × 10^-3 and 1.0 × 10⁰/s. The true stress-true strain curves obtained from the compressive tests revealed a peak stress at the initial stage of deformation. The peak stress decreased with increasing temperature or decreasing strain rate. A close relationship was observed between the peak stress and the constitutive equation for high temperature deformation. In the deformed specimens, fine equiaxed grains were observed with a mean grain size of 330~590 nm, which was much finer than that measured prior to deformation (1.4 μm). A dislocation structure within the grains was also observed in the deformed specimens, indicating the occurrence of dynamic recrystallization during high temperature deformation of the present alloy. The occurrence of dynamic recrystallization was also supported by the existence of a peak stress in the flow curve.