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61.
《Materials Science & Technology》2013,29(12):1793-1797
AbstractThe microstructures and tensile properties of electrodeposited nanocrystalline Ni (nc-Ni) with a broad grain size distribution after annealing at 150, 200 and 300°C for 500 s were investigated. The as deposited broad grain size distribution nc-Ni sample exhibited a moderate strength σUTS of ~1107 MPa but a markedly enhanced ductility ?TEF of ~10%, compared with electrodeposited nc-Ni with a narrow grain size distribution. Annealing below 200°C increased the strength but caused a considerably reduction in tensile elongation. This behaviour is attributed to the grain boundary relaxation and the increased order of grain boundaries after annealing, which can make the grain boundary activities, such as the grain boundary sliding and grain rotations, more difficult. Further annealing at 300°C decreased both the yield strength and tensile elongation significantly due to significant grain growth. 相似文献
62.
Doped SrTiO3 capacitor-varistor multifunctional ceramics were fabricated by a single sintering process.AC complex impedance analysis was performed to investigate electrical features of grains and grain boundaries for both as-reduced ceramic and reoxidized ceramics.The results showed that the as-reduced ceramic exhibited inductive response at high frequencies above 2MHz,which is attributed to the contribution of electron behavior in semiconducting grains.The high frequency inductive response disappeared in impedance plots of reoxidized ceramics. 相似文献
63.
To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium, the tensile behaviors of commercially pure titanium specimens after 91.6% cryorolling and subsequent annealing at 280 ℃, 335 ℃, 450 ℃ and 600 ℃ have been studied. The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size. α grain boundaries are the main dislocation multiplication sources of commercially pure titanium. Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation. Once the applied stress is above the yielding strength, dislocations multiply rapidly and the mobile dislocation density is high. To retrieve the imposed strain rate, the mean dislocation velocity is bound to be low. Therefore, it takes time for them to interact with each other. As a result, the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress. Consequently, the so-called yield plateau behavior presents in the tensile curves. The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test. 相似文献
64.
Grain growth during sintering of the polycrystalline high onset temperature superconductor YBa2Cu3O7−x has been examined by measuring grain sizes at various temperatures for different times above 900°C. The grain size distribution
is found to be predominately lognormal after some sintering time. The mean grain size increases with both temperature and
time. The standard deviation of the grain size distribution increases with temperature, but appears to be independent of time.
The grain growth law may have an exponent of five. The grain growth rate may be affected by the grain size of the calcined
powder. 相似文献
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67.
针对3种不同粒径的高煤级煤开展了甲烷高压等温吸附测试,并对不同粒径煤样甲烷吸附前后的孔隙结构特征进行了对比研究.结果 表明,不同粒径煤样的等温吸附曲线没有显著的差异,随着煤岩粒径的减小,煤岩的吸附速率和最大过剩吸附量呈逐渐增加的趋势.甲烷吸附前后,不同粒径煤样的孔隙结构发生了不同的变化.甲烷等温吸附前,随着煤岩粒径的减... 相似文献
68.
提高430铁素体不锈钢连铸坯等轴晶比例的工艺实践 总被引:3,自引:0,他引:3
通过分析430铁素体不锈钢连铸坯等轴晶比例偏低的影响因素,在电磁搅拌能力不足的情况下,改进工艺,使等轴晶比例得到大幅度提高,减少了铸坯横裂现象。 相似文献
69.
Solute-induced grain boundary(GB) strengthening is eff ective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their potential eff ects on GB binding have been systematically investigated from fi rst-principles energetics. The low-energy Σ3(111) and Σ11(113) are immune to vacancy segregation, while high-energy Al GBs, such as Σ13(320), Σ9(221), Σ5(210), and Σ5(310), can attract both vacancies and... 相似文献
70.