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Nicolás Emanuel Tenaglia Roberto Enrique Boeri Juan Miguel Massone Alejandro Daniel Basso 《Materials Science & Technology》2018,34(16):1990-2000
The austemperability of seven high silicon cast steels with different alloy contents was characteri sed. The maximum round bar diameter that can be fully austempered changed from about 10?mm for an unalloyed steel to more than 70?mm for a low-alloy steel. The austemperability was calculated by applying a procedure based on a standard Jominy test and the characterisation of the microstructure along the Jominy sample. The method, which was validated experimentally, creates a relatively simple procedure to measure austemperability. Processing factors such as the ability of the salt bath to extract heat and the austempering temperature are accounted for the method. The metallographic study revealed the influence of microsegregation on hardenability, which is particularly important for cast steels. 相似文献
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Wei Song Xin-Guang Wang Jin-Guo Li Ye-Shun Huang Jie Meng Yan-Hong Yang Jin-Lai Liu Ji-De Liu Yi-Zhou Zhou Xiao-Feng Sun 《金属学报(英文版)》2020,33(12):1689-1698
Two experimental alloys containing different contents of Ru were investigated to study the effect of Ru on the microstructural evolution during long-term thermal exposure. The increase in Ru promoted the formation of cubical, tiny, and even γ′ phase after full heat treatment. Moreover, the samples after full heat treatment were exposed at 1100 °C for different time. Based on the classical model by Lifshitz, Slyozov, and Wagner, the coarsening of γ′ phase of the alloy containing 2.5 and 3.5 wt.% Ru during the long-term aging was controlled by the interface reaction and diffusion, respectively. The γ/γ′ lattice misfit was more negative with the increment of Ru addition, which induced the formation of stable rafted γ′ phase in the alloy containing 3.5 wt.% Ru at the initiation of long-term aging. Besides, the increase in Ru reduced the diffusion coefficient, which could restrain the γ′ phase coarsening. The lower γ/γ′ lattice misfit of the alloy containing 2.5 wt.% Ru promoted the interface reaction, which induced the rapid coarsening of γ′ phase. Therefore, the increase in Ru improved the microstructural stability of the alloys. On the other hand, the raise of Ru induced “reverse partitioning” behavior, which was effective in suppressing the emergence of the topologically close-packed phase (TCP phase). The TCP phase occasionally occurred in the alloy containing 2.5 wt.% Ru, which was attributed to the high temperature and the supersaturation of the γ matrix. Moreover, the TCP phase was determined as μ phase, which had a high concentration of Co, Re, Mo, and W. A sketch map describing the evolution of the TCP phase was also constructed. 相似文献
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《Ceramics International》2020,46(10):15935-15942
In the present study, the effect of silica nanoparticles on the formation of nano-mullite phase for use in the manufacture of silicon carbide based ceramic foam filters has been investigated. Polyurethane foam filters were impregnated with nanosilica particles by slip casting. In this method, the effect of different percentages of nanosilica particles in the slurry on compressive strength, density and porosity of ceramic foam filters was investigated. The effect of silica nanoparticles on viscosity of slurry was studied using rheometric test. So, sample S15 was selected to proceed. For thermal treatment of ceramic foams, different sintering temperatures were investigated and the best temperature was reported at 1250 °C. Compressive strength results showed that with increasing nano-silica content, CCS increased. XRD results from the samples showed that the nano-mullite phase was formed at 1250 °C along with silicon carbide and alumina phases. Scanning electron microscope images (SEM) showed that the mullite phase was formed in nano-dimensions in ceramic foam bodies. The formation of mullite phase in the microstructure of the filters is one of the factors of strengthening and increased refractory characteristics. EDS analysis by the scanning electron microscopy of the filter which passed ductile iron melt showed that cast iron inclusions and impurities were mostly consisted from FeO, MnO, SiO2, Al2O3, MgO and CO, which were trapped inside the ceramic filter. 相似文献
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本文采用机械合金化工艺制备了两种不同形貌特征的高熵合金(Al0.25Cu0.75FeCoNi)颗粒,一种为椭球状颗粒(平均粒径为53μm,无过程控制剂);另一种为片状颗粒(平均粒径15μm,有过程控制剂)。采用挤压铸造工艺制备了低体积分数(颗粒含量为5 vol.%)的高熵合金颗粒增强铸造铝合金材料,重点分析了不同增强相形貌对复合材料的组织和力学性能的影响规律。结果表明:在复合材料预制块制备过程中,椭球状高熵合金粉体与铝粉容易混合均匀,而片状高熵合金粉体之间易发生团聚。椭球状颗粒与片状颗粒增强的复合材料的抗拉强度分别达到162MPa和174MPa,比铸铝合金实验基体分别提升了12.5%和 20.8%,但伸长率较铸铝合金基体却发生了明显下降。断口分析表明,椭球状颗粒增强复合材料的断裂以基体的撕裂为主;而片状颗粒增强复合材料则以团聚颗粒的破裂为主。 相似文献
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镍基单晶高温合金沉淀相尺度效应研究 总被引:1,自引:1,他引:0
对Ni_3Al(γ')沉淀相尺寸对镍基单晶高温合金拉伸性能的影响进行了研究。对镍基单晶高温合金而言,材料的屈服来源于位错以Orowan机制绕过沉淀相,而Orowan应力与沉淀相间距有关。根据这一机理,基于晶体塑性理论,引入一个本构方程以表征沉淀相尺寸对镍基单晶高温合金屈服强度的影响。采用该本构模型,分别计算了在[001]以及[111]2个取向下,含有尺寸为0.2~2.5μm沉淀相的镍基单晶高温合金屈服强度,并与试验结果进行了对比验证。结果表明,该模型可以准确表征镍基单晶高温合金沉淀相的尺度效应。 相似文献
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