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航天级钛合金的新型叠层制造技术(ALM)的优势体现在较低的制造成本等方面,并可替代传统加工成型工艺。由等离子弧焊熔敷叠层制造技术制备Ti-6Al-4V合金的显微组织由定向凝固生长的β柱状晶及在其晶内生长的细小的α片层组织构成。在原位拉伸过程中结合应用高速离线电子背散射衍射表征(Offline EBSD)可快速获取试样显微组织和形变特征之间的关系。揭示出不均匀变形的发生取决于柱状晶界间的应变响应。柱状滑移和基面滑移系统被激活进而导致最后出现形变滑移线,即在某些柱状晶中滑移扩展至整个晶粒;而在另一些晶粒中表现为存在应变梯度和应力集中的地方发生形变失配。形变的扩展习性受制于定向凝固生长的柱状晶生长方向及其之间的界面取向关系。在垂直于柱状晶方向的拉伸试验揭示存在剧烈的变形局域化。基于原位拉伸观测及高速的离线电子背散射衍射表征结果,本文作者提出从微观到宏观形变扩展的控制机制。
Aerospace grade titanium alloy of the new laminated manufacturing technology (ALM) has the advantage of lower manufacturing costs, etc., and can replace the traditional processing molding process. The microstructure of the Ti-6Al-4V alloy prepared by the plasma arc welding deposition technique is composed of the β-columnar grains grown by directional solidification and the fine α-sheet structure grown in the grains. The relationship between the microstructure and the deformation characteristics of the sample can be quickly obtained by using the high speed off-line EBSD in situ stretching. It is revealed that the occurrence of inhomogeneous deformation depends on the strain response between the columnar grain boundaries. Columnar slip and basal slip systems are activated which in turn leads to the eventual emergence of a slip-line, that is, in some columnar crystals, slip extends to the entire grain; in others, the presence of strain gradients and stress concentrations The place of deformation mismatch. The extended habit of deformation is subject to the direction of columnar growth and the interfacial orientation relationship between them. Tensile testing in the direction perpendicular to the columnar grains revealed the presence of intense deformation localization. Based on in-situ tensile measurements and high-speed offline electron backscatter diffraction characterization, the authors propose a control mechanism extending from microscopic to macroscopic deformation.