热连轧GH4169合金的晶粒长大行为

对热连轧(HCR)GH4169合金在固溶处理过程中晶粒长大行为进行系统研究。结果表明,该合金?相溶解温度在990～1000℃之间,δ相对晶粒长大有显著阻碍作用,在低于δ相溶解温度进行固溶处理时,析出的δ相使得晶粒长大缓慢;在高于δ相溶解温度以上时,晶粒随温度的升高快速长大。晶粒长大动力学表明:在高于δ相固溶线温度以上进行固溶处理时,晶粒生长指数随着固溶温度的升高而增加;固溶处理温度为1000和1050℃时的晶粒长大激活能为223.849kJ/mol,晶粒长大机制为自扩散过程控制机制,并建立了相应的晶粒长大动力学方程。     

薄层铜包钢线钢芯的再结晶晶粒长大规律研究

采用金相分析法研究了薄层铜包钢线钢芯在不同退火温度及保温时间下再结晶及晶粒长大的规律,并在此基础上,对其晶粒生长动力学方程进行了数学回归分析。结果表明:随铜包钢退火温度升高,薄层铜包钢线钢芯组织经历回复-再结晶-晶粒长大的过程,即晶粒尺寸在这一过程中均呈现增加的趋势;晶粒长大动力学方程符合Beck方程,基于Beck方程以及普遍适用性的长大动力学方程进行数值回归分析,计算出再结晶晶粒长大激活能为42.66k J/mol。     

冷旋U-6.5Nb合金再结晶晶粒长大的实验研究

采用冷旋加工-退火工艺细化U-6.5Nb合金晶粒组织,研究旋压变形率、退火温度及退火时间对再结晶后晶粒组织的影响。结果表明,在研究范围内,旋压变形率对晶粒尺寸没有显著影响,随退火温度的升高和退火时间的延长,晶粒尺寸不断长大。在700, 800和900 ℃保温过程中的晶粒长大指数分别为0.47, 0.31和0.34,晶粒长大激活能为100.4 kJ/mol, 表明U-6.5Nb合金的晶粒长大受Nb原子的扩散控制     

FGH96合金晶粒长大规律的研究

对FGH96合金在热处理过程中晶粒长大规律进行了系统的研究。结果表明,γ’相对晶粒长大有显著阻碍作用,在低于γ’相固溶温度(1109℃)热处理时,大量未溶解的γ’相使得晶粒长大缓慢;在高于γ’相固溶温度以上时,合金为单相奥氏体组织,晶粒随温度的升高快速长大。晶粒长大动力学表明：在高于,相固溶温度以上时,晶粒生长指数随着热处理温度的升高而增加;在热处理温度为1135℃和1150℃下的晶粒长大激活能为293．4kJ／mol,晶粒长大机理为自扩散过程控制机理,并建立了相应的晶粒长大动力学方程。     

热处理对C-276合金无缝管晶粒长大行为的影响

研究了不同的热处理工艺对C-276合金冷轧无缝管晶粒长大行为的影响。结果表明:在同一保温时间下,随热处理温度的升高,C-276合金的晶粒尺寸逐渐增大,且不同保温时间下的晶粒长大趋势相同。当热处理温度为1040～1080 ℃时,晶粒长大较快;在1080～1160 ℃时放缓;在1160～1200 ℃时又加快。在1040～1200 ℃下保温10 min后C-276合金的晶界迁移表观激活能为313.77 kJ/mol。当热处理温度为1040～1080 ℃时,随保温时间的延长晶粒长大较为缓慢;温度为1120～1160 ℃时,当保温时间在10 min内,晶粒长大较快,当保温时间大于10 min后晶粒长大减慢;温度升高到1200 ℃时,随保温时间的延长晶粒长大趋势较为平缓。热处理温度在1040～1200 ℃范围内,随温度的升高,C-276合金的晶粒长大动力学时间指数η先增大后减小。     

高温钛合金Ti-60与IMI834的β晶粒长大规律

研究了两种高温钛合金Ti-60和IMI834在不同加热温度和不同保温时间下的β晶粒长大规律.结果表明,在β相区加热时,Ti-60钛合金晶粒尺寸较小,且随加热温度和保温时间的不同变化不大,这主要是由于晶界上富Nd稀土相的存在阻碍了晶粒的长大,而IMI834钛合金的晶粒尺寸随保温时间的增加明显长大.晶粒长大动力学表明,在(Tβ 20 ℃)保温时,两种钛合金β晶粒等温长大曲线近似于抛物线规律,晶粒生长指数n均小于1/2.此外,在加热温度(Tβ～Tβ 40 ℃)范围内、等温时间为10 min时,计算并讨论了Ti-60和IMI834合金的晶粒长大激活能.     

Zn含量对Ag-Cu-Zn合金晶粒长大规律的影响(英文)

对不同Zn含量的Ag-Cu-Zn合金在不同温度、不同热处理时间的晶粒长大规律进行了研究。研究结果表明,随着保温时间的延长,晶粒逐渐长大。在相同保温时间下,Zn含量越高,晶粒长大越明显。随着Zn含量增加,晶粒长大指数n逐渐增大,晶粒长大的激活能Q逐渐降低。     

TC21钛合金β单相区晶粒长大行为研究

研究了高损伤容限型钛合金TC21在单相区不同司加热温度和不同加热时间条件下的β晶粒长大行为.结果表明.在单相区加热.TC21钛合金β晶粒等温长大曲线近似满足抛物线规律.在970、980和990℃等温退火时,晶粒长大指数n分别为0.38、0.34和0.32；晶粒长大激活能为283 KJ/mol.     

TB8钛合金晶粒长大行为的研究

研究了TB8钛合金冷轧板材在不同热处理温度和不同保温时间下的晶粒长大行为。结果表明:TB8钛合金冷轧板材在820~880℃的温度范围内不存在晶粒急剧粗化的现象,可以在此区间内的温度下对其进行热处理,保温时间根据温度的不同可在30~120 min范围内选择。此外,借助Beck方程和Arrhenius方程分别计算得到该合金的晶粒生长指数(n)为0.25~0.35,β晶粒长大激活能(Q)为273.23 k J/mol。     

Ti-1300合金的晶粒长大行为

对Ti-1300合金在固溶处理过程中晶粒的长大行为进行系统研究。结果表明:当固溶温度低于β转变温度时,未溶解的α相使得晶粒长大缓慢;在高于β转变温度固溶处理时,晶粒随着温度升高而快速增大。晶粒长大动力表明:在840~950℃固溶处理时,β晶粒的长大规律可用D=1.13×1010 exp(-2.1×104/T)描述,且晶界迁移的表观激活能为Q=350 k J/mol。当固溶温度为840、870和900℃时,晶粒长大指数随固溶温度升高而增加,分别为0.31、0.55、0.56。     

GH4169高温合金的静态再结晶动力学

对GH4169高温合金在Gleeble-3500热模拟实验机进行了双道次和单道次热压缩实验。分析了变形温度、应变速率、间隔保温时间、变形量和初始晶粒尺寸对GH4169高温合金静态再结晶体积分数的影响。实验结果表明:变形温度越高、应变速率越大、道次间隔时间越长,变形量越大,初始晶粒度越小,静态再结晶体积分数越大。根据实验结果,建立了GH4169高温合金的静态再结晶模型,并将所建立的模型的预测结果和实验结果进行了对比分析,二者比较吻合。     

单晶高温合金再结晶形核条件及长大机制

对DD6单晶高温合金进行表面压痕处理,然后在不同温度(1220、1270和1310℃)热处理2h,研究合金再结晶的形核和长大行为.结果表明:γ'相溶解是再结晶的必要条件;再结晶晶粒以外,产生大量的亚晶界,离压痕中心越近,亚晶界密度越大,亚晶聚合粗化是再结晶的形核和长大机制.在γ'相溶解温度以上,γ'相对再结晶的形核和长大无明显影响.     

Abnormal grain growth and grain boundary faceting in a model Ni-base superalloy

Normal or abnormal grain growth in a model Ni-base superalloy is observed to depend on the grain boundary structure when heat-treated in a solid solution temperature range above the solvus temperature (1150°C) of the γ′ phase. When heat-treated at 1200°C abnormal grain growth occurs and most of the grain boundaries are observed to be faceted by optical microscopy, transmission electron microscopy, and scanning electron microscopy at the intergranular fracture surface. Some of the grain boundary facet planes are expected to be singular corresponding to the cusps in the polar plot of the boundary energy against the inclination angle, and it is proposed that if these boundary segments move by a boundary step mechanism, the abnormal grain growth can occur. When heat-treated at 1300°C normal grain growth occurs, the grain boundaries are defaceted, and hence atomically rough. Normal growth is expected if the migration rate of the rough grain boundaries increases linearly with the driving force arising from the grain size difference. The correlation between the grain boundary structural transition and the growth behavior thus appears to be general in pure metals and solid solution alloys.     

Recovery,recrystallization and grain growth in ordered alloys

The recovery, recrystallization and grain growth behavior of ordered alloys are reviewed from a phenomenological viewpoint. These processes are essentially similar to those occurring in metals except that below the critical ordering temperature their kinetics are much slower, particularly due to the ordered nature of the grain boundaries. Recovery in weakly-ordered compounds below their critical temperature is associated with strain-age hardening whereas more strongly-ordered compounds exhibit recovery softening. An alloy deformed in the ordered state recrystallizes more rapidly than one deformed in the disordered state, a feature associated with a higher stored energy of cold work in the ordered state. Competition between ordering and recrystallization in some strained initially-disordered compounds can cause them not to easily recrystallize in certain temperature ranges, even though they recrystallize readily at both higher and lower temperatures. Antiphase boundaries are relatively scarce in strongly-ordered compounds, but common in weakly-ordered compounds after recrystallization, a feature that may arise because of the (partial) disorder of grain boundaries in the latter materials. Deviations from the stoichiometric composition, because of the increasing disorder, and hence, faster diffusion, generally lead to faster recrystallization and grain growth than at the stoichiometric composition.     

Dynamic recrystallization of single-crystal nickel-based superalloy

The dynamic recrystallization behavior of single-crystal(SC) superalloy SRR99 at low strain rate was investigated by high-temperature creep testing. The results show that dynamic recrystallization may take place after the uncoated samples have been creep-tested in air at high temperature and low stress for a long time. Both the threshold temperature and strain for the dynamic recrystallization of SC superalloy SRR99 at low strain rate are lower than those for the static recrystallization. Dynamically recrystallized grains with the depth less than 15 μm are only located in the surface γ′-free layers, and the recrystallized grains are well-developed grains without columnar γ′ precipitates within them. The dynamic recrystallization behavior of SC superalloy SRR99 at low strain rate is mainly related to high-temperature oxidation. Suitable protective coating can effectively prevent the dynamic recrystallization of SC superalloy components in service. In addition, the dynamic recrystallization behavior of SC superalloy SRR99 at high strain rate was also studied by high-temperature compression testing. At high strain rate, a higher temperature and larger strain are needed for the occurrence of dynamic recrystallization than at low strain rate, and the recrystallized grains have cellular structures with an amount of columnar γ′ precipitates within them.     

时效+再结晶退火对镍基合金锻造混晶组织的影响

为了消减镍基合金锻件中的混晶组织,本文提出了δ相时效+再结晶退火的热处理工艺路线。δ相在时效过程中可以直接析出或者由γ″相发生相变间接析出。对含析出δ相的材料进行高温再结晶退火,然后立即水冷,可以发现时效方式和时效时间对退火过程中的组织演变存在显著影响。时效过程中直接析出的δ相主要分布在晶界,随着时效时间延长部分晶粒内部也会析出δ相,其形貌以短棒状为主。间接析出的δ相主要分布在晶粒内部以及晶界,其形貌主要为晶内长针状以及晶界短棒状。短棒状δ相在退火过程中与位错交互作用较弱,主要起到钉扎晶界的作用;而长针状δ相能够促使亚晶的形成。因此,间接时效方式有利于再结晶形核的发生,并能够有效阻碍晶粒生长避免异常长大的再结晶晶粒。     

Monte Carlo simulation of grain growth and recrystallization in polycrystalline materials

The prediction and control of metal grain structures during processing have been major objectives of materials science. However, methodologies that are accurate and can be easily generalized to a variety of processing conditions have been difficult to formulate due to the complexity of the grain interactions. A novel Monte Carlo-based approach that explicitly incorporates these interactions has been developed to simulate the microstructural evolution driven by the minimization of grain boundary energy and lattice defect density. The applicability of this procedure has been demonstrated by the good correspondence between simulation results and experimental observations. This article reviews recent advances in the application of this technique to the investigation of a variety of phenomena, including normal and abnormal grain growth as well as static and dynamic recrystallization.     

Recovery,recrystallization and grain growth in Fe3Al-based alloys

The recovery, recrystallization and grain growth of particle-free and particle-containing Fe₃Al intermetallics with a total warm reduction of 70% were investigated in the temperature range from 750 to 1115 °C. The physical phenomena during annealing were characterized and analyzed based on the observations of microstructure, measurement of long-range order degree and determination of micro-hardness. The reordering occurs due to the removal of antiphase boundary trails resulting from the dislocation rearrangement during annealing. The micro-hardness depends on both the dislocation density and the change of long-range order degree. The addition of alloying elements affects the dependence of hardness on reordering. It also has a great effect on the recovery and recrystallization. The recrystallized nuclei are formed by preferential subgrain growth and grain boundary migration. Due to strong anisotropy of Fe₃Al-based alloys, the grain boundary migration resulting from inhomogeneous deformation was frequently observed and the distribution of grain size after annealing was also inhomogeneous. The recrystallization kinetics follows the Kolmogorov-Johnson-Mehl-Avrami (KJMA) relationship. Long-range order and second phase are beneficial in decreasing the grain-boundary mobility. The grain growth kinetics of Fe₃Al intermetallics investigated follows the conventional power law equation with a high grain growth exponent of more than 4. Abnormal grain growth in the Fe–28% Al–5% Cr–0.1% Zr–0.5% Mo–0.5% Nb–0.05B% (at.%) alloy was found when it was annealed at 1115 °C for 72 h.     

FGH95高温合金的静态再结晶机制

对热等静压FGH95合金高温挤压形变后的试样进行静态再结晶处理,讨论了其再结晶形核机制及γ′相对再结晶过程的影响.结果表明:合金在γ′相几乎完全溶解温度以上再结晶时,形核以应变诱发晶界迁移机制进行,而在γ′相大量存在的温度范围内则是以亚晶粗化形核机制进行;γ′相的分解速率对再结晶速率有重要影响,随再结晶温度的升高,γ′相分解速率加快,再结晶激活能减小,再结晶速率加快,γ′相分解后以同步或不同步方式重新析出.