材料期刊网

EFFECTS OF OXIDES IN INVESTMENT MOLD ON SURFACE PROPERTIES OF TITANIUM CASTINGS

H.G. Wang , X.M. Qi , J. Tian , W.Q. Zha , G.S. Liang , Y. Y. Chen and J. Jia National Key Laboratory of Precision Hot Processing of Metals , Harbin Institute of Technology , Harbin 150001 , China

金属学报(英文版)

Effects of different facing oxides, including including yttria colloidal and powders (Y/Y), yttria stabilized zirconia colloidal and powders (ZY/ZY), zirconia colloidal and powders (Z/Z) and zirconia colloidal and zireonite powders (Z/ZS) on the qualities of investment castings are studied. The outward appearance, microstructures, and microhardness profiles of castings made of commercial pure titanium, Ti--Al--V and Ti--Al--Zr are investigated. Castings made by shells with yttria as face materials have the least contamination and by zirconite shells have the most contamination. Thermodynamic of metal-mold reactions is also taken into consideration.

关键词: titanium alloy , null , null

Improving glass-forming ability of Mg-Cu-Y via substitutional alloying: Effects of Ag versus Ni

Journal of Materials Research

Based on the best bulk metallic glass (BMG) forming alloy in the Mg-Cu-Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg-(Cu,Ag)-Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg-(Cu,Ag)-Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg-(Cu,Ni)-Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the "confusion principle."

关键词: bulk metallic-glass;shaped copper mold;amorphous-alloys;thermal-stability;ternary-system;casting method;p system;diameter;zr;mm

Ion sputter erosion in metallic glass-A response to "Comment on: Homogeneity of Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass" by L-Y. Chen, Y-W. Zeng, Q-P. Cao, B-J. Park, Y-M. Chen, K. Hono, U. Vainio, Z-L. Zhang, U. Kaiser, X-D. Wang, and J-Z Jiang J. Mater. Res. 24, 3116 (2009)

Journal of Materials Research

The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.

关键词: room-temperature

Corrosion of Y, Fe and Fe-15Y in H_2-H_2S Mixture under 10~(-3) Pa S_2 at 600～800℃

Yan NIU , Weitao WU and Chaoliu ZENG (State Key Lab. for Corrosion and Protection , Institute of Corrosion and Protection of Metals , Chinese Academy of Sciences , Shenyang 110015 , China)F. Gesmundo and F. Viani (Instituto di Chimica , Facolta di Ingegneria , Un

材料科学技术（英文）

The corrosion of an Fe-based alloy containing 15 wt pct Y in H2-H2S mixtures under 10-3 Pa S2 was studied at 600~800℃ in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneflcial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus,Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition. but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12~17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe

关键词:

Achieving high strain rate superplasticity in Mg-Zn-Y-Zr alloy produced by friction stir processing

Scripta Materialia

Friction stir processing was applied to hot-rolled Mg-Zn-Y-Zr alloy to produce a fine-grained structure 4.5 mu m in size with fine, uniformly distributed Mg(3)Zn(3)Y(2) particles and predominant high-angle grain boundaries (HAGBs) of 91%. A maximum superplasticity of 1110% was achieved at a high strain rate of 1 x 10(-2) s(-1) and 450 degrees C. The superior superplasticity at this high strain rate is attributed to the excellent thermal stability of the fine-grained structure and the high percentage of HAGBs. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: Superplasticity;Magnesium alloys;Friction stir processing;Microstructure;Grain boundaries;magnesium alloy;microstructural evolution;powder-metallurgy;behavior;deformation;phase;particles

Corrosion of Y, Fe and Fe-15Y in H-2-H2S mixture under 10(-3) Pa S-2 at 600 similar to 800 degrees C

材料科学技术（英文）

The corrosion of an Fe-based alloy containing 15 wt pet Y in H-2-H2S mixtures under 10(-3) Pa S-2 was studied at 600 similar to 800 degrees C in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneficial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus, Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition, but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12 similar to 17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe.

关键词: high-temperature sulfidation;most-reactive component;ni-nb alloys;h2-h2s mixtures;behavior;600-degrees-c-800-degrees-c;oxidation

Enhanced mechanical properties of Mg-Gd-Y-Zr casting via friction stir processing

Journal of Alloys and Compounds

Mg-10Gd-3Y-0.5Zr casting was subjected to friction stir processing (FSP) at a tool rotation rate of 800 rpm and a traverse speed of 50 mm/min. FSP resulted in the fundamental dissolution of the coarse network-like beta-Mg(5)(Gd,Y) phase and remarkable grain refinement (similar to 6.1 mu m), thereby significantly improving the strength and ductility of the casting. Post-FSP aging resulted in the precipitation of fine beta '' and beta' particles in a fine-grained magnesium matrix, producing an ultimate tensile strength of 439 MPa and a yield strength of 330 MPa. FSP combined with aging is a simple and effective approach to enhancing the mechanical properties of Mg-Gd-Y-Zr casting. (C) 2010 Elsevier B.V. All rights reserved.

关键词: Friction stir processing;Magnesium alloys;Solution;Microstructures;Precipitate;heat-treatment;zn additions;alloy;microstructure;250-degrees-c;precipitation;behavior

稀土Y对镁合金显微组织及腐蚀性能的影响

马宏 , 彭晓东 , 谢卫东

腐蚀学报（英文）

利用对掺法熔铸镁合金AJ61+xY, 研究了合金中相的组成和分布及其在3.5%NaCl溶液中的腐蚀行为. 结果表明, 添加稀土Y使AJ61镁合金的晶粒明显细化,Mg₁₇Al₁₂ 相的数量明显减少且由连续网状变成弥散颗粒状分布,沿晶界处生成耐蚀稀土相Al₂Y、Al₃Y, AJ61镁合金的耐腐蚀性得到明显改善. 耐腐蚀性顺序为:AJ61+1.5%Y>AJ61+2.0%Y>AJ61+1.0%Y>AJ61+0.5%Y.

关键词: Mg-6Al-1Sr 镁合金 , yttrium , microstructure , corrosion resistance

稀土Y对镁合金显微组织及腐蚀性能的影响

马宏 , 彭晓东 , 谢卫东

腐蚀学报（英文）

利用对掺法熔铸镁合金AJ61++xY,研究了合金中相的组成和分布及其在3.5%NaCl溶液中的腐蚀行为.结果表明,添加稀土Y使AJ61镁合金的晶粒明显细化,Mg17Al12相的数量明显减少且由连续网状变成弥散颗粒状分布,沿晶界处生成耐蚀稀土相Al2Y、Al3Y,AJ61镁合金的耐腐蚀性得到明显改善.耐腐蚀性顺序为:AJ61+1.5%Y＞AJ61+2.0%Y＞AJ61+1.0%Y＞AJ61+0.5%Y.

关键词: Mg-6Al-1Sr镁合金 , 钇 , 显微组织 , 耐腐蚀

Processing of nanostructured metals and alloys via plastic deformation

Mrs Bulletin

Plastic deformation can effectively produce nanostructured metals and alloys in bulk or surface-layer forms that are suitable for practical structural or functional applications. Such nanostructured materials are porosity-free and contamination-free, and therefore they are ideal for studying fundamental mechanisms and mechanical properties. In this article, we first give an overview of the principles of grain refinement by plastic deformation and an introduction to the reported processing techniques. Then the four most-developed and promising techniques will be described in detail: equal-channel angular pressing, high-pressure torsion, accumulative roll bonding for bulk nanostructured metals, and surface mechanical attrition treatment for nanostructured surface layers.

关键词: high-pressure torsion;mechanical attrition treatment;ultrafine-grained;materials;bonding arb process;surface-layer;microstructural;evolution;composite conductors;high strains;cu-ag;refinement