共查询到18条相似文献,搜索用时 140 毫秒
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通过Gleeble-3800热压缩模拟试验机对TB17钛合金β相区进行热压缩实验,研究该合金β相区的动态再结晶行为及转变机理。结果表明:TB17钛合金在β相区变形时会发生动态回复(DRV)与动态再结晶(DRX)。不同应变速率下存在两种动态再结晶形核位置,低应变速率下主要在晶粒内部形核,高应变速率下主要在晶界附近形核。通过EBSD和TEM分析可知,在低应变速率下发生连续动态再结晶(CDRX),其发生的主要形式为亚晶合并转动。高应变速率下发生不连续动态再结晶(DDRX),发生的主要形式为晶界剪切伴随着亚晶转动。尽管两种动态再结晶的转变方式不同,其本质都是通过位错的增殖、滑移和胞状结构演化形成新的动态再结晶晶粒。 相似文献
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在变形温度为870~960℃、应变速率为5×10-4 s-1~5×10-2 s-1的条件下对Ti-6Al-4V合金进行单道次等温压缩实验,测出其应力-应变曲线并建立KM模型、Poliak-Jonas模型和Avrami模型,较为系统地描述了这种合金动态再结晶过程中的流变应力、临界应变量、组织演变动力学等的特征。将动态再结晶组织的转变体积分数引入Prasad功率耗散率模型,得到了Ti-6Al-4V合金动态再结晶过程中能量的变化规律并结合微观组织表征揭示了这种合金的动态再结晶机理。结果表明:随着变形温度的提高和应变速率的降低,Ti-6Al-4V合金的动态再结晶临界应变量减小,组织转变的体积分数增大。发生完全动态再结晶时的功率耗散率大于0.34,形核机制为位错诱导的弓出形核机制。 相似文献
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根据形核热力学理论,分析了亚动态再结晶形核的热力学过程,导出亚动态再结晶的临界形核尺寸和形核功均小于动态再结晶的临界形核尺寸和形核功的结论。在变形温度1100℃和变形速率5×10~(-2)s~(-1)条件下对 Cr25Ti 铁素体钢进行双道次热模拟试验,试验验证了上述结论。由于动态再结晶组织中尺寸为 n~*′≤n相似文献
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研究了无限大基体内纳米尺度圆孔表面薄膜中界面螺型位错形核的临界条件,薄膜考虑了表/界面效应。运用弹性复势方法,获得了两个区域应力场的解析解答,并导出位错形核能公式,由此讨论了表/界面效应对薄膜界面位错形核的影响规律。算例结果表明,表/界面效应在纳米尺度下对位错形核的影响显著,不同表/界面效应下位错形核的临界薄膜厚度有很大差异,当基体与薄膜的相对剪切模量超过某一值后,只有考虑负的表/界面应力时位错才有可能形核;薄膜厚度在小于某一临界尺寸时负的表/界面应力更容易位错形核,薄膜厚度大于某一临界尺寸时正的表/界面应力更容易位错形核。 相似文献
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将H59双相多晶黄铜冷轧变形后,进行高密度脉冲电流处理.在透射电镜下观察发现,α β'双相粗晶组织均已发生超细晶化转变,而且在α相晶粒中伴有大量的孪晶.经过预应变处理后,α相在脉冲电流作用下发生再结晶细化,并在随后的α→β相变中进一步发生相变细化;β'相在预应变处理后发生再结晶细化.再结晶细化的原因是,预应变处理使晶体中产生大量的缺陷,极大的增加了形核率,而脉冲电流作用时间短,加热速度快,使晶核长大不充分;相变细化的原因是,高密度脉冲电流改变了相变势垒,促进了高电导率相的形核并抑制其长大. 相似文献
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A Model of Dynamic Recrystallization in Alloys during High Strain Plastic Deformation 总被引:2,自引:0,他引:2
1.IntroductionVerysmallrecrystallizedgrainswereobservedintheadiabaticshearbandsinmetalswhentheywereheavilydeformedathighstrainrates,whichwerezonesofhighlylocalizedplasticdeformation[1~5].Pak[1]foundthatshearbandsinacommerciallypuretitaniumwereconsistedofsmallgrainsof5o~3Oonmindiameterwithwell-definedboundaries.Chokshi[2],And.ade[3jandHinesI4Jalsoobservedtherecrystal-lizedgrainswith1oO~2Oonmdiameterswithintheshearbandsofcopper.Cho151showedthattherewereequiaxedcellswiththesizesof2oo~5oonminth… 相似文献
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采用Gleeble-1500D热力模拟试验机研究新型Al-Zn-Mg-Cu高强铝合金在变形温度为300~450℃,应变速率为0.001~10s~(-1)条件下的热变形组织演化。利用光学显微镜(OM)和透射电子显微镜(TEM)观察合金不同热变形条件下的组织形貌特征。结果表明:随着变形温度的升高和应变速率的减小,位错密度减小,亚晶粒尺寸增大;合金热压缩变形过程中主要的软化机制为动态回复和动态再结晶。变形温度为300~400℃时,主要发生动态回复;变形温度为450℃,应变速率为0.001~10s~(-1)时,软化机制以动态再结晶为主,存在晶界弓出、亚晶长大、亚晶合并3种再结晶形核机制。 相似文献
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Interfacial velocities during grain growth studies of nanocrystalline materials have been investigated. Two types of interfacial
velocity parameters were developed in Ni and Ni–Co alloys. The first was a transformation-averaged parameter based on the
time to consume the nanocrystalline matrix by abnormal grain growth. The second was a time-averaged parameter based on the
rate of size increase of the largest growing grains. Despite the ultra-high driving force and rapid loss of nanostructure
during annealing, the averaged grain boundary velocities are considerably lower than reported velocities during recrystallization
in high purity systems for the same homologous temperature. It was found that the time-averaged abnormal growth front velocity
decreased with increasing migration distance, which was interpreted in terms of a dynamic sulfur segregation model. 相似文献
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Guoliang Hu Yaohua Zhu Guoyi Tang Chanhung Shek and Jianan Liu Materials Department Advanced Materials Institute Tsinghua University Shenzhen China 《材料科学技术学报》2011,(11):1034-1038
Electropulsing-induced recrystallization and its effect on mechanical properties of oriented silicon steel strips (Fe-3.0%Si) were studied by optical microscopy, scanning electron microscopy and electron back-scatter diffraction. The results indicated that electropulsing accelerated recrystallization, and decreased the temperature of recrystallization. Electropulsing favors refinement of the grain structure of the alloy. Effects of electropulsing on strength and elongation of the alloy were discussed from the point view of dislocation dynamics, microstructural changes, and electropulsing kinetics. 相似文献
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《Materials Science and Engineering: A》2006,415(1-2):309-316
By means of the measurement of the creep curve and the observation of SEM and transmission electron microscope (TEM), an investigation has been made into the microstructure evolution and deformation features of AZ31 Mg-alloy during high temperature creep. Results show that the deformation features of the alloy in the primary stage of creep are that significant amount of dislocation slips are activated on basal and non-basal planes, then these ones are concentrated into the dislocation cells or walls as creep goes on. At the same time, twinning occurs as an additional deformation mechanism in the role of the compatibility stress. During steady state creep, the dislocation cells are transformed into the subgrains, then, the protrusion and coalition of the sub-boundaries results in the occurrence of dynamic recovery (DRV). After the dynamic recrystallization (DRX), the multiple slips in the grain interiors are considered to be the main deformed mechanism in the later stage of the steady state creep. An obvious feature of creep entering the tertiary stage is that the cracks appear on the locations of the triple junction. As creep continues, the cracks are viscous expanded along the grain boundaries; this is taken for being the fracture mechanism of the alloy crept to failure. The multiple slips in the grain interiors and the cracks expanded viscous along the grain boundary occur in whole of specimens, that, together with the twins and dynamic recrystallization, is responsible for the rapid increase of the strain rate in the later stage during creep. 相似文献
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Hot deformation of copper-containing microalloyed steels in the two-phase region was carried out to study the effect of copper on transformation and recrystallization behaviour of ferrite in HSLA steels. it was found that presence of copper could decrease the austenite to ferrite transformation temperature. The precipitation of epsilon-copper in ferrite could retard recovery and recrystallization by dislocation and grain boundary pinning in deformed ferrite. Retardation of transformation and ferrite recrystallization resulted in a less mixed structure consisting of fine transformed and recrystallized ferrite in the copper-containing steels. 相似文献