Microstructure and mechanical properties of AZ31 alloy ingot fabricated by semi-continuous casting

The AZ31 alloy ingot with diameter of 110 mm and length of 3500 mm was fabricated successfully. The compositions and microstructure morphologies of the ingot at different locations were performed, which indicated that the chemical composition distributed homogeneously through the whole alloy ingot and the average grain size increased from the surface to the center. The results of the EDS and element face-scanning illustrated that the eutectic compounds mainly consisted of fl-Mg17Al12 and a small amount of fl-Mgl7（AlZn）12. Furthermore, slight improvements of the strength and ductility were observed from the center to the surface along the axial direction of the alloy ingot, while both the strength and elongation to failure of the samples along the radial direction are higher than that along the axial direction. The fine grain strengthening was the main contributors to the strength of the as-casted AZ31 alloy.     

One-step creation of hierarchical fractal structures

Relatively recently, we advanced a route to create, in a controlled fashion, combined horizontal and vertical stratified structures by simple and energy-efficient processing operations employing static mixing elements. While in state-of-the-art static mixing the focus is on layer multiplication, here the aim is to create hierarchical fractal structures. Therefore, the main question addressed in this article is how structures, rather than layers, can be multiplied. The key aspect is the addition of layers on the sides or in the midplane of the flow during the process; every addition step increases the hierarchy by one level. This article derives the general formalism for forming fractal structures with controlled hierarchy, and we develop the language required to design and construct the dies. The main part of the article addresses this main topic and is based on the splitting serpentine static mixer geometry that can be easily made on the parting surfaces of a mold on both the micro- and the macroscale. The second part of the article addresses the strategy to minimize the number of mirroring steps, eventually avoiding mirroring completely, and is based on the rotation-free multiflux static mixer geometry. With the design language derived, complex hierarchical fractal structures can be generated simply by changing the number and sequence of operators within extrusion dies or molds, providing a one-step solution to produce material structures for potential use in diverse applications ranging from advanced mechanical systems to photovoltaic devices, where controlled assembly of dissimilar materials, and the realization of huge interfaces and genuine cocontinuity throughout the cross section, is critical.     

MECHANICAL PROPERTIES AND MICROSTRUCTURES OF Al-Mg-Li-Zr ALLOYS-CONTAINING SILVER

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Processing,deformation, and failure in superplastic aluminum alloys: Applications of orientation-imaging microscopy

The importance of grain size refinement in enabling superplasticity is reviewed, and the current understanding of grain boundary characteristics is summarized. The application of orientation-imaging microscopy (OIM) methods to the processing response and the deformation and failure modes in superplastic aluminum alloys are illustrated through microtexture analysis and determination of grain boundary characteristics in selected commercial materials. Continuous and discontinuous recrystallization reactions exhibit distinct microtextures and grain boundary characteristics. The application of OIM and microtexture analysis to the evaluation of both deformation and failure mechanisms during superplastic forming is illustrated. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

细磨粒超声珩磨ZrO2表面特征研究

采用细粒度金刚石油石，对氧化锆工程陶瓷进行了超声珩磨与普通珩磨的试验研究。试验结果表明，磨削条件对被加工表面的粗糙度和表面破碎影响较大：1)超声珩磨的表面和普通珩磨表面相比，磨削沟槽不仅宽且底部平坦，网纹较均匀，珩磨沟槽的顶部较平整，并且不存在断续现象。2)普通珩磨的延性域加工临界磨削深度不超过1．5m，而超声珩磨方式下，其延性域临界磨削深度可达到3μm。3)普通珩磨方式下，在磨削速度100～150r/m，磨削深度1．0～1．5μm时，可取得较低粗糙度值；超声珩磨方式下，在磨削速度150～190r/m，磨削深度1．0～1．5μm时，取得较低的粗糙度值，同等条件下比普通珩磨低1～2级。     

稀土硼锆在HPb59-1黄铜中的细化变质效果

研究了微量稀土、硼、锆对HPb59-1合金的细化变质作用.结果表明:0.0001%～0.001%的硼具有显著细化变质效果;0.03%～0.05%稀土也能消除铸态柱状晶,但细化晶粒能力远小于微量硼;微量锆细化变质效果不明显.高温(680℃×40min)组织显示,稀土、锆及过量硼的添加,均提高合金α→β转变温度,从而影响热加工性能.     

微量硼在HPb59-1黄铜中的细化变质作用

研究了微量硼对HPb59-1合金的细化变质作用。结果表明:0.0001%￣0.0010%的硼具有显著细化变质效果,使发达的柱状晶转化为30￣50μm的等轴晶;高温(680℃×40min)组织显示,微量硼的铸态细化变质组织在高温有较好的热稳定性,对α→β转变影响较小。但过量硼的添加,将减缓α→β转变,提高转变温度,从而影响热加工性能,为此,硼添加量应小于0.001%。     

热处理对Al-9.0Zn-2.5Mg-1.2Cu-0.12Sc-0.15Zr合金组织与性能的影响

通过差热分析和X射线衍射分析及硬度、拉伸性能和电导率测试,研究了热处理工艺对A l-9.0Zn-2.5M g-1.2Cu-0.12Sc-0.15Zr合金组织及性能的影响。结果表明:合金的峰值时效工艺为:120℃×22 h;综合性能最佳的热处理工艺为:120℃×22 h+180℃×30 m in+120℃×22 h的回归再时效处理(RRA)。经RRA处理,合金的σb为733.4 MPa,δ为5.4%,电导率为37.6%IACS。     

宽板弯曲成形过程中板厚变化精化模型

基于弹塑性力学基本理论,在考虑板材真实本构关系基础上建立了宽板板厚变化精细化模型。同时,借鉴分三层思想,较好地考虑了宽板在弯曲成形过程中部分纤维层应力反号过程,因此具有较好的精确性和较强的普适性。最后,以铝板为例进行分析,发现计算值和实验值吻合较好。本文研究成果为深入研究弯曲变形过程和科学制定弯曲成形工艺具有一定的理论价值和实用意义。     

中硅钼球墨铸铁的研制

根据国外相关技术标准，设计、研制了中硅钼球墨铸铁，并测试、分析了其铸态组织、力学性能、抗高温氧化性能。结果表明，该成分的材料在铸态下完全符合技术要求。