共查询到20条相似文献,搜索用时 15 毫秒
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Zi-You Ding Lan-Yue Cui Rong-Chang Zeng Yan-Bin Zhao Shao-Kang Guan Dao-Kui Xu Cun-Guo Lin 《材料科学技术学报》2018,34(9):1550-1557
Exfoliation on as-extruded Mg-1 Li-1 Ca magnesium alloy was investigated after an immersion in 3.5 wt%NaCl aqueous solution for 90, 120 and 150 days through optical microscope, digital camera, scanning electron microscope, electrochemical workstation, scanning Kalvin probe, X-ray diffraction and Fourier transform infrared spectroscope. The results demonstrated that exfoliation corrosion occurred on extruded Mg-1 Li-1 Ca alloy due to elongated microstructure parallel to surface, and delamination of lamellar structure resulted from galvanic effect and wedge effect. Skin layer with fine grains exhibited better corrosion resistance, whereas the interior with coarse grains and the intermetallic compound,Mg_2 Ca particles existing in a fibrous structure, dispersed along grain boundaries and extrusion direction in a line. Furthermore, galvanic effect between Mg_2 Ca particles and their neighboring a-Mg matrix facilitated dissolution of Mg_2 Ca particles and a-Mg matrix; wedge effect was caused by formation of corrosion products. Exfoliation corrosion of extruded Mg-Li-Ca alloys might be a synergic effect of pitting corrosion,filiform corrosion, intergranular corrosion and stress corrosion. Finally, exfoliation corrosion mechanism was proposed. 相似文献
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为了研究中频电磁场对7050铝合金凝固组织和元素分布的影响,在未施加电磁场,施加1000Hz、6000A电磁场和1000Hz、4000A电磁场下进行7050铝合金凝固试验.利用金相显微镜和电子背散射衍射分析技术分析了锭坯微观组织,利用化学分析方法测定溶质元素沿锭坯边部到中心的分布情况.结果表明:外加中频电磁场有效地细化晶粒,影响溶质元素分布.未施加电磁场下,锭坯晶粒最大,发生反偏析;1000Hz、4000A电磁场下,锭坯晶粒次之,发生反偏析;1000Hz、6000A电磁场下,锭坯晶粒最细,发生正偏析. 相似文献
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溶胶-凝胶法在纳米粉体制备中的应用 总被引:7,自引:2,他引:7
溶胶-凝胶法是制备纳米粉体的一种低温工艺,具有制品纯度高、化学均匀性好、颗粒细、可容纳不容性组分和不沉淀组分、掺杂分布均匀、合成温度低、成分容易控制、工艺设备简单等优点。本文介绍了溶胶-凝胶法的概念、工艺原理及其在TiO2、ZrO2、BaTiO3、Al2O3等纳米粉体制备方面的应用,提出了溶胶-凝胶法制备纳米粉体的局限性及发展方向。 相似文献
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变形Al-Sr中间合金的变质遗传效应 总被引:11,自引:0,他引:11
经变形处理后的Al-5%Sr中间合金与未变形的相比,具有明显的变质效果差异在砂型条件下,用Al-5%Sr中间合金对共晶Al-Si合金进行变质处理,加入含锶量为0.1%的锭料,变质度为5级;加入变形处理的中间合金时,含锶量仅为0.05%时变质度为5级,含锶量为0.06%即达到最佳变质效果,为5.5级在金属型条件下,加入含锶量为0.06%的锭料与加入含锶量0.03%的变形处理的中间合金的变质效果相当,都为6级这种变质效果的差异是Al-5%Sr中间合金的组织遗传效应造成的 相似文献
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轻水反应堆(LWR)是国际上多数核电站采用的堆型。锆具有良好的加工性能,优良的机械性能,较高的熔点、优异的耐蚀性能及核性能,被用作燃料包壳和堆芯结构材料,是发展核电及核动力舰船不可替代的关键结构材料和功能材料。随着核电技术的发展,对堆芯包壳材料性能提出了更高的要求,综述了核用锆合金包壳材料的国内外研究和使用现状以及新型SiC包壳材料的研发现状。总体来说,锆合金在未来几十年内仍是核反应堆包壳材料的主要用材,开展新合金的研发,不断提升锆合金的性能是世界各国研究者共同的目标;适时加大投入力度,强化条件建设,就能加快具有国内自主知识产权锆合金的产业化步伐,可最终实现核电及核动力用锆合金材料的自主化;SiC材料具有更高的熔点、更好的耐腐蚀性能,是一种极具应用潜力的材料,有可能成为第4代核反应堆的包壳材料,但还需投入大量研究。 相似文献
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A. Sanschagrin R. Tremblay R. Angers D. Dub 《Materials Science and Engineering: A》1996,220(1-2):69-77
Magnesium-lithium base alloys containing aluminum, silicon and rare-earth additions have been prepared by melting and solidification in a low-carbon steel crucible, homogenized at 350°C and extruded at the same temperature. The distribution of alloying elements in homogenized specimens was determined and the microstructure of these alloys characterized. The mechanical properties were measured and compared with those of similar alloys. 相似文献
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Effects of calcium on the microstructures and tensile properties of Mg-5Li-3Al alloys 总被引:2,自引:0,他引:2
Tao WangRuizhi Wu Milin ZhangLi Li Jinghuai ZhangJiqing Li 《Materials Science and Engineering: A》2011,528(18):5678-5684
The as-cast Mg-5Li-3Al-xCa (x = 0, 0.5, 1, 1.5 wt.%) was prepared with vacuum induction melting furnace, then processed by hot extrusion. The microstructures and tensile properties were investigated. The results show that the grains of as-cast alloys were refined gradually with the increase of Ca content from 0.5 wt.% to 1 wt.%, while the Ca content increases to 1.5 wt.%, the grain size increases. The microstructures of investigated alloys were further refined after hot extrusion. Both as-cast and as-extruded Mg-5Li-3Al-0.5Ca alloys have the highest mechanical properties, which is mainly attributed to the grain refinement caused by the addition of Ca and the formation of strengthening phase, Al4Ca. When the addition of Ca is up to 1-1.5 wt.%, the tensile properties of alloys are worsened due to the excessive (Mg, Al)2Ca eutectic phase forming at grain boundary. 相似文献
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1. Introduction Light rare earth addition can remarkablyenhance the service life of Fe-Cr-Al alloyfor electrical heating element, but itscontent in the alloy must be controlledbelow the level of 0.1 wt-%. When thecontent exceeds that, the performance 相似文献
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《Materials Science & Technology》2013,29(12):1846-1850
AbstractAdding KBF4 salt to molten Al produces a B lean Al–B melt and a B rich dross. A revised practice that relies on the co-addition of Na3AlF6 with KBF4 and mechanical stirring is proposed in the present work to produce Al–B alloys. The highly surface active Na3AlF6 helps to break up the boride agglomerates glued together by the spent salt. Mechanical stirring facilitates uniform distribution of the freed borides in molten aluminium. The microstructural features of the Al–3B alloy thus processed and the B recovery were improved in a marked fashion. The boride dispersion in the aluminium matrix was uniform with no evidence of salt residues inside the aluminium matrix. An improved salt addition practice to ensure full B recovery and an Al–B alloy of sufficient quality is thus claimed to comprise the following steps: melting commercial purity aluminium ingot, adding premixed KBF4 and Na3AlF6 salts to molten Al at 800°C gradually to avoid excessive cooling of the melt, holding the melt for 5 min at 800°C to allow the reaction to reach completion, decanting the spent salt and throughly stirring the melt before casting into desired shape. 相似文献
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通过场发射扫描电子显微镜(FESEM),X射线衍射仪(XRD),能量色谱仪(EDS)分析Al-5Ti-1B,Al-4Ti-1C和Al-5Ti-0.8B-0.2C中间合金的微观组织与物相组成,比较研究3种中间合金对7050铝合金晶粒尺寸与力学性能的影响。结果表明:Zr的存在削弱了Al-5Ti-1B和Al-4Ti-1C中间合金的细化效果,而对Al-5Ti-0.8B-0.2C中间合金细化效果影响较小。含掺杂型TiC粒子的Al-5Ti-0.8B-0.2C中间合金具有较好的抗Zr"中毒"能力,加入量为0.2%(质量分数,下同)时,含Zr7050铝合金平均晶粒尺寸由200μm细化至(60±5)μm,室温极限抗拉强度由405MPa提高到515MPa,提高了27.2%,伸长率由2.1%提高到4.1%。而加入0.2%的Al-5Ti-1B或Al-4Ti-1C中间合金时晶粒尺寸较粗大且分布不均匀,表现出明显的细化"中毒"。 相似文献
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Absract The impact of thermosolutal convection during directional solidification is explored via results of numerical investigations.
Results from fully transient numerical simulations of directional solidification in a differentially heated cavity under terrestrial
conditions and Bridgman cytstal growth in space are discussed. The pivowl role ofboth thermaland solutal convection in the solidifaction process is illustrated by examining these two cases. In particular, radical and longitudinal
macrosegregation resulting from this thermosolutal convection is discussed. 相似文献