Introducing β-Ti ductile-zones for enhancing both strength and ductility in heterostructured titanium alloy composites

Breaking trade-off barriers of strength-ductility in Ti alloys and their composites has been a key challenge for their engineering applications. Herein, we developed a new strategy of introducing β-Ti ductile zones in heterostructured (Cu@CNTs/TC4)+TC18 composites, which were synthesized using two-stepped ball milling, spark plasma sintering and hot rolling processes. Such composites are composed of TC18-coarse grain zones (CGZ) and (TiC+α'')-reinforced TC4-fine grain zones (FGZ). They achieve an exceptional high strength and high ductility, which are superior to those of TC4 alloys and homogeneous Cu@CNTs/TC4 composites. Heterogeneous interfacial microstructures of TC4-FGZ/TC18-CGZ play an important role in strengthening and toughening effects. The grain-coordinated deformation between TC18-CG and TC4-FG is also the key reason for achieving an exceptional ductility.

突破钛合金及其复合材料的强塑性权衡瓶颈，始终是其工程应用面临的核心挑战。本研究提出一种在异质结构(Cu@碳纳米管(Carbon Nanotubes, CNTs)/TC4)+TC18复合材料中引入β-Ti塑性区的新策略，该复合材料通过两步球磨、放电等离子烧结(Spark Plasma Sintering, SPS)及热轧工艺制备而成。该复合材料由TC18粗晶区(Coarse Grain Zone, CGZ)与(TiC+α'')增强的TC4细晶区(Fine Grain Zone, FGZ)组成，可实现优异的高强度与高塑性，综合性能优于纯TC4合金及均质Cu@CNTs/TC4复合材料。TC4细晶区与TC18粗晶区之间的异质界面微观结构，对材料的强韧化效应具有关键作用；而TC18粗晶粒与TC4细晶粒之间的晶粒协调变形，同样是实现优异塑性的核心原因。