Ti14钛合金半固态下的变形行为研究

研究了Ti14钛合金半固态条件下的变形行为。半固态变形后．由于液相的出现，加快了原子扩散的能力．其变形激活能明显高于钛合金固态变形时的激活能。结果表明，变形后，晶界、晶内液相长大，形成了宽化的晶界和网格状结构。     

EBSD技术研究Ni-48Al金属间化合物超塑变形组织演变

采用电子背散射衍射(EBSD)技术研究在1075℃、初始应变速率1.5×10-3s-1条件下大晶粒Ni-48Al合金超塑变形过程中的组织演变。结果表明,变形前,大晶粒Ni-48Al合金以大角度晶界为主,小角度晶界比例极低。在超塑变形过程中,持续有取向差≤5°的小角度晶界产生。随变形量的增大,新形成的小角度晶界取向差增加,转变为取向差6°~15°小角度晶界,进而转变为取向差>15°的大角度晶界。小角度晶界的产生速率与小角度晶界转变为较大角度晶界的速率趋向一动态平衡。小角度晶界向较大角度晶界不断转变的结果使大角度晶界数量不断增加,最终导致晶粒显著细化。     

形变及冷却速率对热轧超高强汽车钢板中纳米析出的影响

为精确控制热轧780 MPa级Nb-Ti微合金化C-Mn钢中的纳米析出物(Nb,Ti)C,利用热力模拟实验技水,通过透射电镜观察及统计分析,研究形变及冷却速率对纳米析出的影响规律.结果表明,形变可显著地提高析出物形核率,并细化析出物平均直径;析出物数量随冷却速率的增大逐渐减小;既定的实验条件下,冷却速率达到15℃/s可完全抑制析出物在冷却过程中形核;随着冷却速率的增大,析出物的形核区间由奥氏体区形核向铁素体或贝氏区转变,析出物平均直径明显细化;在低冷却速率条件下的变形实验钢中,形变提高组织中的空位浓度,促进析出物空位形核的发生;晶界或亚晶界是过饱和空位的主要陷阱,但空位的扩散活性很高致使低冷却速率条件下晶界或亚晶界附近的空位浓度低于析出物形核的临界形核浓度,从而无法形核,形成晶界附近无析出带;无析出带宽度随冷却速率的增大而减小,这归因于空位扩散活力随冷却速率的增大而降低.     

Ti40阻燃合金粗晶超塑性变形行为及机理

借助OM、TEM研究了高温条件下Ti40阻燃合金的粗晶超塑性变形行为及机理。结果表明:在920℃下,应变速率为5×10-5～1×10-2s-1的Ti40合金表现出良好的超塑性行为,拉伸延伸率均超过250%,应变速率敏感指数m大于0.3。超塑变形后,粗大的等轴组织细化。TEM分析表明,在变形过程中,位错运动形成亚晶界,亚晶界通过吸收滑移位错形成小角度晶界甚至大角度晶界。Ti40合金的粗晶超塑性是由动态回复和再结晶共同作用的结果。     

冷却方式对半固态Ti14合金微观组织的影响

采用OM,SEM,XRD研究不同的冷却方式炉冷(Furnace Cooling,FC)、空冷(Air Cooling,AC)和水淬(Water Quenching,WQ)对半固态Ti14合金微观组织形貌以及相组成的影响。结果表明:3种冷却方式均没有改变合金的相组成,但影响Ti2Cu相的形态和分布。炉冷后,Ti2Cu相以颗粒状按一定位向析出,并排列形成条状和树枝状;空冷后,Ti2Cu相以颗粒状和层片状分布于晶内和晶界;水淬后,晶界液相特征明显,晶内和晶界无明显析出。分析认为:半固态Ti14合金冷却过程中经历了包晶凝固,包晶反应发生在液相/β/Ti2Cu三线交点处,使得三线交点处的溶质分布很不规则,包晶相的形核和生长形态发生改变,同时,冷却方式不同影响包晶反应程度,从而影响后序的共析组织,使得不同冷却方式冷却后产生了不同的组织形貌。     

扩展路径低温ECAP及时效热处理对Cu0.6Cr合金的组织和性能影响

采用光学显微镜和X射线衍射仪对Cu0.6Cr合金经低温扩展路径等通道转角挤压（ECAP）后的组织演变规律进行了研究。采用扫描电子显微镜和能谱仪研究了Cu0.6Cr合金经不同时效热处理条件后的晶粒大小、析出相分布规律和断裂特征。并且分别测试了合金经低温ECAP和低温ECAP+时效热处理后的抗拉伸强度、硬度和导电率。结果表明,Cu0.6Cr合金经低温ECAP变形后形成明显细化且相互交割的纤维组织,并且合金在变形中始终保持（111）面的择优取向。时效热处理的合金变形量越大,析出相的数目和尺寸就越大,第二相析出速率也越快。5道次合金经450 ℃时效2 h后的抗拉伸强度为568.1 MPa,维氏硬度为1624.8 MPa,导电率为82%IACS。     

Microstructure evolution during phase separation in Ti-Zr-C

(Ti,Zr)C powder was synthesized by carbothermal reduction and subsequently aged at 1150–2000 °C. The phase composition and microstructure was investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction. It was found that the as-synthesized (Ti,Zr)C particles have a concentration gradient with a higher concentration of Ti at the surface of the particles. Furthermore, during aging the (Ti,Zr)C decomposes into Ti-rich and Zr-rich lamellae. During aging at 1400 and 1800 °C for 10 h, most Zr-rich and Ti-rich domains precipitate at grain boundaries, inheriting the crystal orientation of the parent grain behind the growth front. When the precipitate grows into another (Ti,Zr)C grain, that grain adopts the same crystal orientation as the parent grain. The crystallographic misorientation between adjacent lamellae is 0–5°. Based on these microstructural observations it is hypothesized that the mechanism of decomposition is discontinuous precipitation.     

铸态2219铝合金热压缩变形组织演变规律

为解决2219铝合金微观组织粗大、第二相分布不均的问题,开展了对铸态2219铝合金热压缩变形组织演变规律的研究。研究结果表明,经热压缩变形后,铸态2219铝合金组织中粗大的晶粒及连续网状分布的残余结晶相被打碎,经热处理后形成了均匀的再结晶组织。随着变形温度的升高,晶粒组织粗化,但Al2Cu相的分布更细小、均匀;随着变形量的增大,晶粒组织逐渐细化,晶粒大小分布也更均匀,且Al2Cu相也随变形量的增加破碎得更充分,分布更细小、均匀。在大直径铸锭锻造开坯过程中,为了获得Al2Cu相细化分布的组织,变形温度应控制在420℃以上,单次变形量不应低于50%。延长锻后保温时间不会显著影响材料的显微组织,因此,在锻造开坯过程中,为了保证合理的变形温度区间,可以采用回炉加热多火次锻造的方式。     

Structure of martensite in sputter-deposited (Ni,Cu)-rich Ti–Ni–Cu thin films containing Ti(Ni,Cu)2 precipitates

The martensite structure in sputter-deposited thin films of Ti_48.6Ni_35.9Cu_15.5 was studied. The Ti(Ni,Cu)₂ phase precipitates during the annealing process. Fine Ti(Ni,Cu)₂ precipitates can be deformed by the shear deformation of martensitic transformation, but they obstruct the movement of the twin boundaries to some extent. Coarse Ti(Ni,Cu)₂ precipitates seriously impede the growth of martensite plates and lead to a rectangular-cell-like structure of martensite in the film annealed at 873 K. The resistance of Ti(Ni,Cu)₂ precipitates to the growth of the martensite plates enhances with the coarsening of Ti(Ni,Cu)₂ precipitates, which is one of the reasons for the decrease in the maximum recoverable strain with increasing annealing temperature. B19′ martensite with (0 0 1) compound twinning is frequently observed near coarse Ti(Ni,Cu)₂ precipitates and grain boundaries in films annealed at 873 and 973 K. The local stress concentration should be responsible for the presence of B19′ martensite.     

钛的电阻钎焊技术研究

研究了Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ和Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ金属间化合物合金的热轧组织与性能,结果发现：随着变形量的增加,两种合金第二相Ｔｉ５Ｓｉ３变得细小且趋向于均匀分布。变形量越大,合金的室温四点弯曲程度越大,含Ｔｉ５Ｓｉ３较多的Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金的弯曲强度较高。两种合金的室温弯曲断口形貌均为准解理形式,两相界面结合较强。高温拉伸试验表明：随变形量的增大,Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的拉伸强度和塑性都增加。Ｔｉ－２４Ａｌ－１１Ｎｂ－５Ｓｉ合金由于变形量较大和较高的强化相体积含量,拉伸强度明显较Ｔｉ－２４Ａｌ－１１Ｎｂ－２Ｓｉ合金的为高,但塑性却大为降低     

超细晶工业纯钛的变形、应变速率敏感性和激活体积

在温度为250~450 ℃、应变速率为1×10-4-1 s-1的条件下,对超细晶工业纯钛进行变速率压缩实验,计算超细晶工业纯钛的应变速率敏感性因子和激活体积,并研究超细晶工业纯钛的变形行为。研究结果表明：超细晶工业纯钛在稳态变形阶段存在流变软化效应,这是受变形过程中大角度晶界和位错活动所控制的。超细晶工业纯钛的应变速率敏感性因子和激活体积在数值上都相对较低,应变速率敏感性随着变形温度的升高而增加,但激活体积独立于变形温度。应变速率敏感性和激活体积的数值表明晶粒内部位错之间的交互作用几乎不发生,而位错与晶界之间的交互作用显著影响超细晶工业纯钛的塑性变形。     

Inconel783高温合金螺栓的组织与织构

研究了Inconel783高温合金螺栓的组织结构与织构特点,重点关注β相的分布与析出特征,并研究了高温应力松弛前后组织与织构的变化情况。结果表明,螺栓试样γ相晶粒分布较为均匀,同时存在弥散分布的γ′相析出。大颗粒的β相沿螺栓轴向成串分布,其分布特征与γ相晶粒取向及尺寸无关,主要由冶炼方式与热加工过程决定;较小的β相在γ相晶界与晶内、连续或孤立析出。织构方面,γ相与β相均未表现出强织构,与热加工过程中变化的多向应力状态有关。以螺栓轴向(x方向)为试样参考方向,γ相存在一定的<111>//x与<100>//x择优,其中前者强度稍高。高温应力松弛试验后,γ相组织、β相分布与各相织构均较为稳定。对该合金中发挥重要作用的小尺寸β相分析发现,其析出行为受到γ相基体取向与晶界特征影响,其中<111>取向晶粒内析出较多,孪晶界上β相析出不占优势。因此,通过控制热加工与固溶处理过程中γ晶粒尺寸与取向择优,有望调控其析出特征。     

Cu—Ti合金原位生成TiB2颗粒时的组织演变

通过原位生成反应,采用Cu-3．4％Ti和Cu-0．7％B中间合金,利用快速凝固技术制备纳米TiB,颗粒增强块体Cu—Ti合金,然后对合金在900℃进行热处理l～10h。高分辨透射电镜（HRTEM）观察表明,在铜熔体中,Ti和B通过原位反应生成初始纳米TiB2颗粒和TiB晶须,TiB晶须的生成会导致TiB2颗粒粗化。初始TiB2颗粒沿晶界分布,会阻碍晶粒在高温下的生长。在对合金进行热处理时,晶粒内的Ti和B原子通过扩散反应生成二次TiB2颗粒。对合金热处理前后的导电率和硬度进行测试。结果显示,生成的二次TiB2颗粒能够延缓合金在高温下硬度的下降,合金的电导率和硬度随着热处理时间的延长而增加,在处理8h时分别为33．5％IACS和HVl58。     

冷拉伸预变形及热处理对Hastelloy C-276合金晶界特征的影响

对Hastelloy C-276合金分别进行2%、6%、14%、22%、30%和54%冷拉伸预形变后经1100 ℃×15 min等温退火并水冷,采用EBSD技术分析变形量对其合金晶界特征分布和晶粒尺寸的影响。结果表明,随着变形量的增加,总的特殊晶界比例呈先下降后上升最后下降的趋势。当变形量为14%时,总的特殊晶界比例出现峰值点,达到了64.8%,同时Σ1晶界比例出现拐点,呈下降趋势,变形储存能得以释放,有利于特殊晶界的产生。此时,晶粒组织处于再结晶初始阶段。但大变形条件下的退火并不利于特殊晶界比例的提高。随着晶粒尺寸的增加,退火孪晶密度降低,选择适当的晶粒尺寸有利于晶界特征分布优化。     

GRAIN REFINEMENT OF MICROALLYED STEEL THROUGH HEAVY HOT DEFORMATION AND CONTROLLED COOLING

1.IntroductionAsfinegrainedsteelsshowmanyfaVowhlemechanicalpropertiessuchassbength,ductility,impactproperty,etc,grainrefinementhasbeenanimportantitemamongresearchstudies.Niohitunisveryoftenaddedtoimprovestrengthandlow--temperaturetoughnessOfTMCPsteelsbyinhibitingausteniterecrystallizationandgrain~dabingthermomechAncaltreatment.ItisgenerallybelievedthatthehanimtunferritegrainsizeofcommercialTMCPsteelsrangesfrom3to5Urn['--3),butithasbeenrePOrtedthatthefenitegrainsizecanbereducedto1--ZUmusi…     

Effects of Ti and(or) Cu on microstructures and magnetic properties of sintered Nd-Fe-B magnets

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Discontinuous precipitation at the deformation band in copper alloy

The Cu-Ni-Si alloy is known as a precipitation hardening alloy, where the Ni₂Si intermetallic compound is precipitated in the matrix during aging. There are two types of precipitation of Ni₂Si: continuous and discontinuous cellular. The discontinuous cellular precipitation is generally initiated at interfaces especially grain boundaries in the matrix. To observe the grain boundary effect on the discontinuous precipitation, a large-grained Cu-Ni-Si-Ti alloy was intentionally fabricated by unidirectional solidification and plastically deformed by groove rolling. While discontinuous cellular precipitation has been generally known to occur only at the high angled grain boundaries in the alloys, we found that it was also generated inside the grains, at the deformation bands formed by plastic deformation.     

TC4/ZrO2复合材料激光近净成形微观组织分析

采用激光近净成形系统成形了不同ZrO_2掺入量的TC4/ZrO_2薄壁,研究了扫描速率对金属基陶瓷材料成形热应力的影响,利用X射线衍射仪(XRD)、扫描电镜(SEM)、X射线能量色散谱仪(EDS)对薄壁样件进行相组成分析、微观组织观察以及元素分布检测。研究表明,相对较低的扫描速度可以减小薄壁件的残余应力,抑制样件的宏观裂纹;XRD结果显示当ZrO_2含量达到30%以上时,生成了TiO.325的Ti的非化学计量氧化物;TC4基体的微观组织随着ZrO_2掺入量的增多晶粒逐渐从针状过渡到板条状、块状;EDS结果显示当Ti晶粒为板条状,晶界间有ZrO_2富集;随着ZrO_2含量增多,Ti固溶体中固溶的Zr增多。本研究为最终成形TC4/ZrO_2梯度材料提供了可靠的技术支持。     

Cracking Behavior of Cr2O3 Scales on Fe–25Cr Alloys Under Creep Deformation at 973 K in Ar Atmosphere

An Fe–25Cr alloy was oxidized in Ar at 973 K with or without external stresses of 30, 35, and 40MPa. A 0.1-m thick Cr₂O₃ scale was formed during pretreatment, after which it grew obeying a parabolic rate law without formation of flaws, i.e., cracks and exfoliation. After the pretreatment, tensile stresses of 30, 35, and 40 MPa were applied to monitor cracking behavior of the oxide scale. Cracking commenced at the alloy grain boundaries by the end of a second-stage creep. In a third stage, cracks formed in the alloy grains, arrayed almost perpendicular to the direction of the tensile stress, with regular intercrack spacings. The average intercrack spacings (L) at grain boundaries are smaller than the intercrack spacing of the grains, and the spacings are given by the power law relation: L()ⁿ, with strain rate exponents n of -0.22 for grains and –0.44 for grain boundaries. It appears that the local strain rate at grain boundaries is much larger than that of the grain as well as that the toughness of the oxide formed on the grain boundaries may be less than that of the grains. Indentation with a Vickers micro hardness tester indicated that the adhesion and fracture toughness of the oxide scale decreased both with growth of the oxide scale and creep deformation of the alloy substrate.     

Deformation of nanocrystalline binary aluminum alloys with segregation of Mg,Co and Ti at grain boundaries

The influence of the temperature and sort of alloying element on the deformation of the nanocrystalline (NC) binary Al alloys with segregation of 10.2 at % Ti, Co, or Mg over grain boundaries has been studied using the molecular dynamics. The deformation behavior of the materials has been studied in detail by the simulation of the shear deformation of various Al bicrystals with the grain-boundary segregation of impurity atoms, namely, Ti, Co, or Mg. The deformation of bicrystals with different grain orientation has been studied. It has been found that Co introduction into grain boundaries of NC Al has a strengthening effect due to the deceleration of the grain-boundary migration (GBM) and difficulty in the grain-boundary sliding (GBS). The Mg segregation at the boundaries greatly impedes the GBM, but stimulates the development of the GBS. In the NC alloy of Al–Ti, the GBM occurs actively, and the flow-stress values are close to the values characteristic of pure Al.