缺口对TC21钛合金全片层组织拉伸性能的影响

研究了缺口对具有全片层组织的TC21钛合金的拉伸性能的影响,采用扫描电镜(SEM)观察分析了其显微组织和断口形貌特征,计算出了不同退火状态下TC21合金的缺口敏感性系数,并建立TC21钛合金显微组织-缺口拉伸性能的定量关系。结果表明:缺口半径对全片层组织的TC21钛合金的拉伸强度和塑性有显著的影响;随缺口半径的增大,合金拉伸强度逐渐下降,塑性也降低,没有出现"缺口强化"效应;随退火温度增加,全片层组织的TC21钛合金的缺口敏感性减小;缺口对TC21合金的微观断裂机制影响不大,主要为准解理和延性断裂两种混合断裂机制,但随着缺口半径增加,合金断口的宏观特征脆性倾向越明显。     

X70管线钢电化学充氢后的力学行为研究

应用拉伸试验和慢拉伸试验，研究X70管线钢电化学充氢后材料拉伸性能的变化．结果表明：电化学充氢对X70管线钢的强度没有显著的影响，主要降低了材料的塑性，从而降低了材料的断裂延性和断裂强度．在静态电化学充氢条件下，材料的塑性随充氢时间的增加，依次降低．在慢拉伸条件下，动态电化学充氢显著降低材料的塑性．断口分析表明：静态电化学充氢后的断口以韧窝为主要特征，但韧窝直径变小；慢拉伸的动态电化学充氢断口出现准解理断裂．     

显微组织对TC11合金高温保时疲劳敏感性的影响

详细研究了等轴、三态、网三种组织对ＴＣ１１合金（Ｔｉ－６．５Ａｌ－３．５Ｍｏ－１．５Ｚｒ－０．３Ｓｉ）５２０℃高温保时疲劳敏感性的影响。结果表明,当在每次循环峰值保时３ｍｉｎ时,三种显微组织的ＴＣ１１合金均呈现疲劳寿命显著下降,其中等轴组织下降最大,三态组织其次,网篮组织最小。ＳＥＭ和ＴＥＭ观察显示,等轴和三态组织的保时敏感性是以大量准解理断裂和车辙状平面滑移为其断裂特征,且准解理断裂和平面滑移随     

静液挤压93W合金变形与断裂研究

对静液挤压93W合金的微观组织、力学性能、变形与断裂特征进行了分析研究。结果表明：钨合金的强度随挤压变形量的增大而增加，其增加的幅度随挤压变形量的增大而减小，而延伸率则随挤压变形量的增大而减小；变形起始于粘结相，合金的变形属于典型的双相协调变形；裂纹萌生于钨．钨界面之间；静液挤压态钨合金的拉伸断口上钨颗粒解理断裂的比例明显高于未变形态。     

固溶处理对Ti-22Al-25Nb合金棒材组织与拉伸性能的影响

以Ti-22Al-25Nb合金棒材为试验对象,研究了固溶温度对合金棒材组织和室温拉伸性能的影响。结果表明:随着固溶温度的升高,α2/O相颗粒含量明显减少,B2相体积分数增加;合金的拉伸性能也随之变化,强度随固溶温度的升高而增加,塑性略有下降;断口形貌显示,Ti-22Al-25Nb合金在拉伸断裂过程中以准解理断裂为主。     

TC11钛合金中氧铝偏析与脆性断裂

借助ＳＥＭ及ＥＤＡＸ、ＡＥＳ对某些ＴＣ１１钛合金棒材机械性能差的原因进行了研究。。结果表明材料延伸率、断面收缩率及冲击值低，显微硬度值高的拉伸和冲击断口上都呈现脆性解理断裂的断裂源，源区显微组织为条状α及空洞，且氧铝偏高。氧铝偏高造成α＋β→β相变温度和再结晶温度升高，使加工变形中形成的条状α在随后的热处理中得不到改变，并导致拉伸、冲击时的脆性断裂     

一种镍基第三代单晶高温合金的横向拉伸性能

在760℃到1100℃条件下,研究了一种镍基第三代单晶高温合金的横向拉伸性能。采用光学显微镜(OM)、场发射扫描电子显微镜(FESEM)与扫描透射电子显微镜(STEM)观察了合金的显微组织与断口形貌。结果表明：随着温度的升高,合金的拉伸强度降低,而拉伸延伸率增加。在760℃与850℃条件下的拉伸断裂均为类解理断裂。在980℃,1070℃和1100℃条件下,试样断口出现了反映凝固方向的枝晶形貌特征,且随着温度的升高枝晶形貌在断口上的面积增加。在980℃条件下,拉伸断裂为类解理断裂与韧窝断裂的混合断裂。在1070℃与1100℃条件下,拉伸断裂均为韧窝断裂。随着温度的升高,塑性变形过程中开动了更多滑移系,导致形成了不同的位错形貌。760℃拉伸,合金中出现了高密度大致平行分布的a/2<110>位错;980℃拉伸,合金中出现了位错缠结;1100℃拉伸,合金中形成了位错网络。     

温度对DO3型Fe—28Al合金力学性能的影响

研究了ＤＯ３型Ｆｅ－２８Ａｌ有序合金在２５￣６００℃温度范围内加热时温度对合金拉伸特性和断裂行为的影响，加热有利于合金强度和塑性的改善，合金的断裂行为也随温度的提高由穿晶解理型向韧窝型转变；不同温度下力学性能的变化趋势取决于合金的有序程度。     

循环次数对TC4钛合金组织和力学性能的影响

通过显微组织观察、室温拉伸和SEM断口扫描,研究了循环次数对TC4合金组织和力学性能的影响。研究结果表明,随着循环次数的增加,TC4合金的强度略有降低,伸长率和断面收缩率明显升高,条状α组织长径比逐渐减小,并部分球化;拉伸断口断裂形式由未循环时的解理断裂→解理+韧窝断裂→韧窝断裂转变。     

Sb对AZ80镁合金显微组织和力学性能的影响

研究了Sb对AZ80镁合金显微组织和力学性能的影响。结果表明,当加入0.5%Sb时,AZ80镁合金的晶粒最细小,冲击韧度和拉伸强度都达到最大值,硬度达到最低值。继续增大Sb含量,合金的冲击韧度和强度降低,硬度增加。而且Sb的加入可使镁合金的拉伸断口由解理断裂转变为准解理断裂。     

温度和氧含量对Ti-2Al合金拉伸力学行为和断裂方式的耦合影响

研究高氧含量(0.30%,质量分数,下同)、工业水平氧含量(0.16%)和极低氧含量(0.06%) 3种Ti-2Al合金在低温(77 K)、室温和高温(673 K)下的拉伸力学行为。结果表明：低温和室温下,随着氧含量的升高,材料强度提高,塑性降低。然而,高温673 K下,不同氧含量Ti-2Al合金强度和塑性基本相同,材料强度和塑性对氧含量的依赖性显著降低。氧含量较低时,温度对Ti-2Al合金塑性影响很小。微观组织观察表明,随着温度的升高,工业水平及高氧含量Ti-2Al合金拉伸断口由脆性解理转变为延性韧窝。高温环境下,固溶氧原子扩散速率提高使Cottrel气团对位错滑移的阻碍减弱,均匀变形的结果导致高氧含量Ti-2Al合金延性改善。     

Reaction synthesis of Ni/Ni3Al multilayer composites using Ni and Al foils: High-temperature tensile properties and deformation behaviour

The effects of temperature on the tensile properties and deformation behaviour of Ni/Ni₃Al multilayer composites have been systematically investigated. With increasing tensile test temperature from room temperature to 600 °C, the ultimate tensile strength decreased. The ‘abnormal’ strengthening of Ni₃Al gave rise to a reduction in the capability for cooperative deformation between the Ni and the Ni₃Al layers at elevated temperatures. As a result, the ultimate tensile strength of the multilayer composites decreased at elevated temperatures. A mixture of transgranular cleavage and intergranular failure at relatively low temperatures, and an intergranular failure at elevated temperatures were observed in the fracture surfaces of the Ni₃Al layers in the multilayer composites. The splitting of the coarse precipitates along the {0 0 1} planes at 800 °C resulted from the differences in solubility of Al in Ni between room temperature and 800 °C.     

EFFECT OF CHROMIUM AND BORON ON ENVIRONMENTAL EMBRITTLEMENT OF FORGED Fe_3Al

1.IntroductionIronaluminidesbasedonFe3AlandFeAlhaveexcellentresistancetooxidationandrelativelylowcost,whicharepr0misingcandidatesforuseasastructuralmaterialincor-rosiveenvir0nmelltsl1'2].H0wever,thesealloyshaven0tyetfoundwidespreadusebecausetheyexhibitpoorductilityatambienttemperatures,accompaniedbybrittlefracture-Thebrittlebehaviorhasrecentlybeenattributedt0environmenta1embrittlementinvolvinggen-eration0fatomichydr0genatthecracktipwhichisthentransportedintothespecimenduringloadingpr0ducingb…     

Effects of deviations from stoichiometry on the strength anomaly and fracture behavior of B-doped FeAl

Tensile tests were conducted at temperatures ranging from 145–1123 K on four different FeAl alloys, containing 40, 43, 45, and 48 at.% Al, each doped with 0.12 at.% B. The alloys were initially heat treated to obtain a relatively large grain size (˜200 μm), after which they were given a long, low-temperature anneal (673 K for 5 d), to minimize, respectively, the effects of grain boundary strengthening and thermal vacancies on the measured yield strengths. Each alloy displayed bcc-type behavior at low temperatures (yield strength decreasing with increasing temperature), followed by a strength anomaly at intermediate temperatures (yield strength increasing with increasing temperature), and a sharp drop in yield strength at elevated temperatures (beyond the anomalous strength peak). Thermal vacancies that are generated during the hold time at the test temperature may contribute to the production of the strength anomaly. In specimens not given the vacancy-minimizing anneal, quenched-in vacancies were found to substantially increase low-temperature strength, thereby masking the yield strength anomaly. As the Al concentration of FeAl increased, the prominence of the yield strength anomaly decreased. Ductility also exhibited a peak at elevated temperatures, first increasing with temperature until it reached a maximum value and then decreasing with further increases in temperature. The peak in ductility occured at lower temperatures as the Al content increased. The fracture mode in all four alloys was mixed (intergranular + transgranular) at cryogenic temperatures, predominantly intergranular at around room temperature, dimpled rupture at peak ductility, and intergranular cavitation at elevated temperatures where the ductility dropped.     

挤压态Mg-10Gd-3Y-0.5Zr镁合金的低温力学性能(英文)

研究多循环低温交变(液氮浸泡处理)和拉伸温度对挤压态Mg10Gd3Y0.5Zr镁合金的微观组织、力学性能以及断裂机制的影响。结果表明,Mg10Gd3Y0.5Zr合金经10d液氮浸泡或10个周期高低温交变循环后,合金室温力学性能基本不变;而经过20个周期高低温循环后,合金的室温抗拉强度由398MPa升高到417MPa。在196°C下拉伸时,挤压态Mg10Gd3Y0.5Zr镁合金的屈服强度和抗拉强度均大幅度提高,分别为349MPa和506MPa,分别增长了18%和27%。合金室温断裂机制为穿晶解理断裂,而低温条件下为韧性断裂和解理断裂并存的混合断裂机制。     

Damping behavior and mechanical properties of Mg-Cu-Mn alloy processed by equal channel angular pressing

Equal channel angular pressing(ECAP) was conducted at 250℃for 4 passes to the as-extruded Mg-3%Cu-1%Mn alloy with high strength and high damping capacity.After ECAP processing,the grain of as-extruded alloy is significantly refined to about 4μm,both yield strength and tensile strength of the as-extruded Mg-Cu-Mn alloy are decreased,but the ductility is improved.After the ECAP processing,the damping capacity of Mg-Cu-Mn alloy is decreased at room temperature,while is substantially increased at elevated te...     

成形气氛中氧含量对激光沉积TA15钛合金组织及力学性能的影响

采用激光沉积制造技术制备了TA15钛合金厚壁件,通过光学显微镜(OM)和扫描电子显微镜(SEM)及拉伸试验对其显微组织、断口及力学性能进行分析,研究成形气氛中氧含量对激光沉积TA15钛合金组织及力学性能的影响。结果表明:随着气氛中氧含量增加,沉积态和退火态试样的显微组织均为典型网篮组织无明显变化。沉积态试样的室温抗拉强度提高而塑性下降,氧含量保持在5×10~(-5)以下能获得较好的综合力学性能。退火态试样的显微硬度低于沉积态且两者均随氧含量增加逐渐提高。室温拉伸断口的断裂机制随着氧含量增加由韧性断裂变为半解理半韧性断裂。     

Fracture Features and Substructures of Ti-Al Ca Alloy

ＦｒａｃｔｕｒｅＦｅａｔｕｒｅｓａｎｄＳｕｂｓｔｒｕｃｔｕｒｅｓｏｆＴｉＡｌ＋ＣａＡｌｏｙＣａｏＰｅｎｇ，ＨｕａｎｇＢａｉｙｕｎ，ＨｅＹｕｅｈｕｉａｎｄＣｈｅｎＬｉｎｇｈｕｉ（曹鹏）（黄伯云）（贺跃辉）（陈令晖）ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒ...     

Temperature dependent mechanical properties of ultra-fine grained FeCo–2V

The tensile properties of ultra-fine grained ordered FeCo–2V have been investigated as a function of testing temperature. Samples with grain sizes of 100, 150 and 290 nm have been tested at temperatures ranging from 25 to 500 °C. Extremely high yield strengths (up to 2.1 GPa) were measured at room temperature with appreciable ductility of between 3 and 13%. These strengths were found to decline only gradually as the testing temperature was increased to 400 °C, while ductility was generally enhanced, up to 22%. The high strengths are attributed to grain boundary strengthening that is particularly effective due to ordering. Measured ductility was dependent on the relative values of yield strength, fracture strength and work hardening rate. Discontinuous yielding and appreciable Lüders strain (3–6%) were observed and were dependent on the initial structure and on the testing temperature.     

Effects of vanadium and titanium on mechanical properties of low carbon as cast microalloyed steels

Abstract

Tensile, hardness and room temperature Charpy V notch impact tests were conducted to evaluate the variations in the mechanical properties of a low carbon cast steel containing vanadium and combinations of vanadium and titanium in the as cast condition. Tensile and hardness test results indicated that good combinations of strength and ductility can be achieved by microalloying additions. The effect of titanium on the yield strength and hardness, however, strongly depended on Ti/N ratio. Ti in hyperstoichiometric amounts increased the yield strength and hardness whereas in hypostoichiometric amounts, it did not have a considerable effect on those properties. Scanning electron microscopy and optical microscopy studies revealed that coarse TiN particles were responsible for this behaviour. On the other hand, microalloying additions significantly decreased the room temperature impact energy and led to the dominance of cleavage facets on the fracture surfaces. Although coarse TiN particles were identified to act as cleavage nucleation sites in the Ti bearing heats, no distinct microstructural feature could be identified as cleavage initiators in the microstructure of the alloy containing only vanadium.