共查询到20条相似文献,搜索用时 140 毫秒
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本工作采用熔体急冷装置对过共晶铝硅熔体进行深过冷处理,采用光学显微镜、扫描电子显微镜和X射线衍射仪等手段,研究了硅含量和熔炼工艺对熔体深过冷过共晶铝硅合金凝固组织的影响。研究结果表明,合金在800℃熔炼,保温时间为30 min时,熔体深过冷处理可抑制Al-(14~18) Si合金熔体在凝固过程中初晶硅的析出。当Al-18Si合金在800℃熔炼,保温时间超过30 min时,深过冷Al-18Si合金熔体在室温金属模型中凝固时可完全抑制初晶硅的析出,获得无初晶硅的凝固组织。 相似文献
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电磁场技术在半固态合金加工中的应用促进了制备工艺的开发和创新,也为获得高质量的半固态合金制品提供了保障。电磁场引起的半固态合金熔体流动状态和性质对合金元素传输、晶粒长大、温度场分布、凝固组织等均有重要影响。主要综述了电磁场对半固态合金流动行为的影响、数值模拟技术在解析半固态合金流动行为中的应用等方面的研究进展,并结合笔者的研究经历介绍了电磁场搅拌技术在半固态合金浆料制备中的应用、熔体流动对半固态合金凝固组织的影响,以及在半固态合金熔体流动特性研究中的新发现。在这些研究工作的基础上,着重综述了应用商业软件和数学建模对半固态合金熔体中电磁场作用引起的流动行为进行模拟、仿真所做的工作和取得的成果。最后,对电磁场技术在半固态合金加工中的应用以及电磁场作用下半固态合金熔体流动特性对半固态合金凝固组织影响的研究进展进行了总结,并对其发展前景和主要发展方向进行了展望。 相似文献
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稀土对铝硅共晶熔体的物性及凝固组织的影响 总被引:1,自引:0,他引:1
通过测量不同含Ce,La量的Al-Si共晶合金熔体的密度,粘度和电阻率,考察了熔体的物性变化与凝固组织之间的相关关系,结果表明,物性变化的转折点与共晶Si形貌的改变具有对应的关系。 相似文献
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采用玻璃包覆法(fluxing)提纯和在不同温度下保温,获得了Fe40Ni40P14B6合金熔体的凝固组织,研究了过冷度对凝固组织的影响.结果表明,随着过冷度的增大,Fe40Ni40P14B6的凝固组织从亚共晶转变为共晶组织,晶粒尺寸明显减小.当过冷度超过某一临界值时,合金熔体发生Spinodal分解,形成网状结构的凝固组织并使晶粒显著细化,达到纳米尺度.在深过冷条件下,可获得块体纳米晶凝固组织. 相似文献
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为了解Pr对Sn-Cd包晶合金凝固组织的作用,在不同抽拉速率下对Sn-Cd-Pr合金进行定向凝固实验.采用光学显微镜、扫描电子显微镜(SEM)和能谱分析(EDS)研究了Pr对Sn-Cd包晶合金凝固组织的影响.研究发现:对于Sn-1.8%Cd过包晶合金,在2μm/s时0.5%的Pr增加了包晶相β的体积分数;在4μm/s时凝固组织明显细化.对于Sn-0.65%Cd亚包晶合金,在4μm/s时Pr的加入促进了平→胞界面的转变;在16μm/s时随着Pr含量的增大,凝固组织逐渐细化;在100μm/s时Pr含量的增大使凝固组织仅有微弱的细化.研究表明,Pr的加入可以改变组成相的体积分数、细化组织以及减小界面稳定性. 相似文献
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深过冷定向凝固工艺过程的研究 总被引:3,自引:0,他引:3
利用过冷度的遗传性,提出了将合金熔体深过冷与传统定向凝固相结合的深过冷定向凝固技术,并在自制的实验装置上,对SDS技术进行了探索性研究,实现了Cu与w(Ni)为5.0%合金的深过冷和深过冷定向凝固。 相似文献
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AbstractMn-90.4 wt% Sb alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this hypoeutectic alloy. The macrostructures on the longitudinal section of the alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields. 相似文献
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Qiang Wang Tie Liu Chao Zhang Ao Gao Donggang Li Jicheng He 《Science and Technology of Advanced Materials》2009,10(1)
Mn-90.4 wt% Sb alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this hypoeutectic alloy. The macrostructures on the longitudinal section of the alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields. 相似文献
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Microstructure and crystallographic orientation of directionally solidified Mg-4 wt% Zn alloy were characterized by X-ray computed tomography (XCT) and electron backscatter diffraction (EBSD) in this study. Results reveal that Mg-4 wt% Zn alloy with dendritic microstructure exhibits typical basal texture along growth direction. Based on this, the effect of grain orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy in 0.9 wt% NaCl solution was investigated. Result shows that oriented planes have better corrosion resistance than and ones, which is attributed to a synergistic effect of surface energy, atomic packing density and the stability of oxidation film. 相似文献
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用金相、扫描和透射电镜研究了690合金经1450-1550℃,5 min熔本过热处理对合金再结晶组织和显微硬度的影响。结果表明,690合金中凝固析出的TiN的体积分数和平均尺寸随着熔体过热温度的升高而降低,其形态由规则的块状转变为颗粒状。经均匀化退火后,TiN的体积分数有所增加,而平均尺寸却有所降低。再结晶退火的过程中有大量亚微米尺度的Ti(C,N)弥散析出,其析出量随着熔体过热温度的升高而增加,这些细小的Ti(C,N)粒子可以起到沉淀强化的作用,提高690合金的显微硬度。 相似文献
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采用布里奇曼定向凝固技术制备了NiNi3Si亚共晶复合材料,系统地研究了Ni-Ni3Si亚共晶的定向凝固组织特征。在较低的凝固速率R=3μm/s时亚共晶成分的合金为规则的层片共晶组织。随着凝固速率的增大,当R=8μm/s时,平界面失稳,在第二相的旁边出现浅胞状组织。当R=25μm/s时在析出相的旁边出现了突起的胞状组织。当R=40μm/s时由于固液界面前沿的成分过冷逐渐增大,凝固组织生长成为典型的树枝晶组织。并根据"成分过冷"判据,评估了固液界面前沿的"成分过冷"的大小,理论计算与实验结果基本吻合。此外,根据BH模型计算和比较了α-Ni相的界面生长温度和共晶界面生长温度,证明较高速定向凝固下不太可能制备出全耦合生长的共晶组织。随凝固速率的增大,一次枝晶间距减小,组织细化。 相似文献
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采用Gleeble 1500热模拟机对定向凝固Fe-6.5%(质量分数)Si合金进行热压缩变形研究。结果表明,Fe-6.5%(质量分数)Si合金柱状晶组织热形变过程中很难发生动态再结晶,以动态回复为主,易产生严重的变形带;在无序相区间,在柱状晶晶界处发生动态再结晶形核,但长大受到限制,仅局限于晶界附近。与锻态等轴晶组织相比,有序相区间,两种组织形变行为基本一致,受温度影响剧烈,在无序相区间,随温度升高,等轴晶组织的形变激活能略有升高,平均值约为294kJ/mol,而柱状晶组织的形变激活能逐渐降低,平均值约为260kJ/mol。 相似文献
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The influence of melt superheating treatment on the solid/liquid (S/L) interface morphology of directionally solidified Ni-based superalloy DZ125 is investigated to elucidate the relationship between melt characteristic and S/L interface stability. The results indicate that the interface morphology is not only related to the withdrawal velocity (R) but also to the melt superheating temperature (Ts) when the thermal gradient of solidification interface remains constant for different Ts with appropriate superheating treatment regulation. The interface morphology changes from cell to plane at R of 1.1 μm/s when Ts increases from 1500°C to 1650°C, and maintains plane with further elevated Ts of 1750°C. However, the interface morphology changes from coarse dendrite to cell and then to cellular dendrite at R of 2.25 μm/s when Ts increases from 1500°C to 1650°C and then to 1750°C. It is proved that the solidification onset temperature and the solidification interval undergo the nonlinear variation when Ts increases from 1500°C to 1680°C, and the turning point is 1650°C at which the solidification onset temperature and the solidification interval are all minimum. This indicates that the melt superheating treatment enhances the solidification interface stability and has important effect on the solidification characteristics. 相似文献
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用液态金属冷却技术(LMC)和传统的定向凝固技术(HRS)制备了名义成分为Ni-33Al-31Cr-2.9Mo-0.1Hf-0.05Ho(%,原子分数)的定向合金,研究了制备工艺对其组织的影响.结果表明,合金由初生NiAl枝晶、NiAl/Cr(Mo)共晶胞和少量Hf同溶体组成.与HRS工艺相比,LMC工艺能提高同液前沿温度梯度和冷却速度.较高的固液前沿温度梯度扩大了NiAl/Cr(Mo)共晶共生区成分范围,减少初生NiAl枝晶的体积分数.而较高的冷却速度抑制固溶元素扩散,细化定向合金的组织,增加合金中固溶元素总量.另外,LMC工艺能避免HRS工艺中产生的生长缺陷,包括斑点,NiAl一次枝晶的偏转和NiAl一次枝晶的不连续. 相似文献