共查询到18条相似文献,搜索用时 46 毫秒
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采用选晶法在改进型Bridgman定向凝固炉中制备镍基单晶高温合金DD403,利用电子探针(EPMA)技术研究了DD403合金在枝晶生长条件下的显微偏析。结果表明,随着抽拉速率增加DD403的偏析程度逐渐加剧。偏析于枝晶间元素Al、Ti和枝晶干元素Co、W的偏析程度随着抽拉速率的增加而增大,而合金元素Mo和Cr的偏析比接近于1,基本不存在偏析,且偏析比随抽拉速率增加没有明显变化。研究结果同时表明,随着抽拉速率增加DD403的共晶含量逐渐增加。 相似文献
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采用OM,SEM以及EPMA等手段对比研究了不同热等静压温度对第三代单晶高温合金DD10组织的影响。结果表明:在150MPa压力条件下,1290℃热等静压即可使第三代单晶高温合金DD10中的显微疏松完全闭合;随热等静压温度的升高,共晶体积分数逐渐减少,热等静压温度达到1310℃及以上温度,共晶完全溶于基体。在1340℃/150MPa热等静压后,合金中出现局部初熔。热等静压后DD10单晶高温合金的γ′相立方度提高,不同热等静压温度对γ′相的形貌影响基本相同。热等静压降低了DD10单晶高温合金的枝晶偏析,并且热等静压温度越高,枝晶偏析改善越明显。 相似文献
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一种镍基单晶高温合金凝固组织的截面尺寸效应 总被引:1,自引:0,他引:1
采用快速凝固法拉制壁厚分别为0.8,1.5,2.5mm的单晶薄壁试样,研究了一种镍基单晶高温合金凝固组织的截面尺寸效应.结果表明:随截面尺寸减小,不同厚度薄壁试样凝固组织一次枝晶间距减小,二次枝晶间距先增大后减小;相对于15mm试样,薄壁试样枝晶干处γ′相尺寸变小,枝晶间γ′相尺寸变化不大,γ/γ′共晶含量明显减少.能谱分析表明不同厚度薄板试样元素偏析程度相对于15mm试样均得到一定缓解,但各不同厚度试样元素偏析变化不大.对三种厚度薄板试样进行真空固溶热处理后发现共晶已基本消除,而15mm试样还残留少量共晶. 相似文献
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概述了目前国内外镍基单晶高温合金定向凝固数值模拟的研究进展,定向凝固过程的数值模拟由宏观向微观转变,详细介绍了微观组织数值模拟的几种主要方法:决定论方法、随机论方法和相场方法,评述了这几种方法的特点以及局限性,指出宏观和微观现象的完整耦合可以对镍基单晶高温合金凝固过程做出更加准确的模拟预测。 相似文献
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镍基单晶高温合金研究进展 总被引:1,自引:0,他引:1
单晶高温合金因具有较高的高温强度、优异的蠕变与疲劳抗力以及良好的抗氧化性、抗热腐蚀性、组织稳定性和使用可靠性,广泛应用于涡轮发动机等先进动力推进系统涡轮叶片等部件。由于采用定向凝固工艺消除了晶界,单晶高温合金明显减少了降低熔点的晶界强化元素,提高了合金的初熔温度,能够在较高温度范围进行固溶和时效处理,其高温强度比等轴晶和定向柱晶高温合金也大幅度提高。经过几十年的发展,单晶高温合金已经在合金设计方法、组织结构与力学性能关系、纯净化冶炼工艺和定向凝固工艺等方面取得了重要进展。从单晶高温合金成分特点、合金元素作用、强化机理、力学性能各向异性、凝固过程及缺陷控制、单晶制备工艺等方面,简要介绍了单晶高温合金的主要研究进展。 相似文献
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Jian Zhang ) Jinguo Li ) Tao Jin ) Xiaofeng Sun ) Zhuangqi Hu ) ) Institute of Metal Research Chinese Academy of Sciences Shenyang China ) Graduate University of Chinese Academy of Sciences Beijing China 《材料科学技术学报》2010,26(10):889-894
A single crystal Ni-base superalloy was processed with withdrawal rates between 2 and 7 mm/min.The ascast microstructures,heat treatment response and creep property have been characterized as a function of the withdrawal rate.As expected,the primary and secondary dendrite arm spacing decreased with increasing withdrawal rate;microsegregation degree and porosity distribution were also varied with different withdrawal rates.The withdrawal rate of 2 mm/min resulted in a noticeable residual microsegregation eve... 相似文献
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The solid-liquid(S/L) intedecial morphology of a single crystal superalloy DD8 has been in-vestigated. The evolutive behavior of cellular morphology with tilted preferred crystallographic orientation near cell-dendrite transition was dynamically observed, and the efFect of crystallo-graphic orientation on primary dendritic arm spacing has been examined. The experimental results show that for planar and cellular morphology no any S/L interfacial anisotropy exists,but near cell-dendrite transition, the S/L intedecial anisotropy appears and gives rise to the cellular crystal fingers tilted from thermal flow direction to preferred crystallographic orientation.The crystal fingers with their preferred orientation parallel to DS growth direction are more stable than that with tilted orientation. For the tilted fingers, the sudece on the side facing DS growth direction is less stable than that on the reverse side, the different stability on the two sides will lead to forming unsymmetrical dendritical microstructure. With the increase of tilted angle of preferred crystallographic orientation, the primary dendrite arm spacing decreases. 相似文献
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针对单晶高温合金精铸薄壁试样制备困难的问题,建立了薄壁板形试样的有限元模型,采用ProCAST数值模拟的方法模拟DD6单晶精铸薄壁板形试样的定向凝固过程,研究了几何形状和工艺参数对定向凝固过程中温度场、温度梯度场及糊状区的影响。结果表明:薄壁板形试样中间部位工作端的温度梯度在60~65℃/cm范围内,糊状区固相线较为平直,液相线的位置在近炉壁一侧较低,远炉壁一侧较高。几何形状对单晶高温合金试样定向凝固过程有重要影响,提高浇注温度或降低抽拉速率有助于薄壁板形试样固液界面前沿液相温度梯度增大、糊状区宽度减小。单晶高温合金精铸薄壁试样定向凝固过程数值模拟结果与实际浇注结果吻合,凝固过程数值模拟为单晶精铸薄壁试样的制备提供了技术支持。 相似文献
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The Ni-base single crystal superalloy was bonded by the transient liquid phase(TLP) bonding,using a Ni-base flexible metal cloth as an insert alloy.TLP bonding of superalloy was carried out at 1473-1523K for 0.5-24h in vacuum.The [001] orientation of each test specimen was aligned perpendicular to the joint interface.The bonded region was observed by optical microscopy, and the microstructural and compositional analyses across the bonded interlayer were performed by using a scanning electron microscopy(SEM) .The electron back scattering diffraction(EBSD) method was applied to determine the crystallographic orientation.The resultsindicated that the chemical homogeneity across the bonded region can be achieved,and γˊphase both in the bonded interlayer and in the superalloy substrate is almost identical,while the bonded interlayer had almost matched the crystallographic orientation of the bonded substrates. 相似文献
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利用ZM定向凝固装置研究了镍基单晶高温合金DD3在高温度梯度(700~1200K/cm)定向凝固条件下的微观组织演化特征及其对工艺参数的响应函数,结果表明:该合金在高界面温度梯度条件下,柱晶生长速度范围向高速区扩展,从而使单晶亚结构细化成为可能。所得单晶棒中亚结构一次间距可比传统HRS法定向凝固籽晶中相应尺度减小5~10倍。本文还对其组织演化机制进行了分析。 相似文献
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