增材制造TiB/Ti复合材料网状组织形成与力学性能

Network formation and mechanical property of additive manufactured TiB/Ti composites

采用快速凝固技术将TiB直接植入基体钛合金,形成一种新型超细网状结构钛基复合材料(titanium matrix composites,TMCs)粉体,并采用激光增材制造技术,制备出一种等轴网状和柱状网状组织交替分布的新型钛基复合材料,系统分析和讨论增材制造TMCs超常凝固网状组织形成机制与力学特性。研究发现:增材制造TiB/Ti复合材料网状组织(约9μm)主要由原位自生纳米TiB晶须组成,呈现B27和Bf两种晶体结构;B元素的直接引入,易于在凝固界面形成成分过冷,不仅促使交替形成等轴网状组织和柱状网状结构,也同步细化基体晶粒尺寸,实现基体合金片层α相的等轴化。经原位力学观察分析发现,增材制造形成的原位自生纳米TiB网状组织结构,不仅能够抑制裂纹偏转并钝化裂纹,还将大量滑移迹线聚集于网络结构内部,并在晶界诱发高密度位错,限制材料的塑性变形,大幅度提高了复合材料的强度,增材制造TiB/Ti复合材料抗拉强度提高42%,伸长率保持在约10%。

TiB was planted into the matrix titanium alloy through the rapid solidification process,and the new ultrafine network reinforced titanium matrix composites(TMCs)powder was formed.Based on the laser additive manufacturing technology,a new titanium matrix composite with alternate distribution of equiaxed network and columnar network structure were creatively fabricated,the formation mechanism of the network structure was systematically discussed,and the mechanical properties of the super-solidified TMCs by additive manufacturing were tested.The results indicate that the network structure(about 9μm)of the additively manufactured TiB/Ti composites is mainly composed of in-situ nano-TiB whiskers,presenting two crystal structures of B27 and Bf.The direct introduction of B element is easy to form constitutional supercooling at the solidification interface.The equiaxedαphases are obtained by promoting the alternating formation of equiaxed/columnar network structure and refining the grain size.In addition,the formed nano-TiB network structure,not only inhibits the crack deflection and passivate cracks,but also confines the large number of slip lines inside the TiB network structure via in-situ observation,inducing high-density dislocations at the grain boundaries,which limites its plastic deformation,and greatly improves the strength of the composites.The additively manufactured TiB/Ti composites increases the tensile strength by 42%,and maintains the elongation of about 10%.