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，一直是制约其工程应用的核心难题。本研究提出了一种在异质结构(Cu@CNTs/TC4)+TC18复合材料中引入β相钛（β-Ti）韧塑区的新策略，该复合材料通过两步球磨、放电等离子烧结（Spark Plasma Sintering, SPS）与热轧工艺制备得到。该复合材料由TC18粗晶区（Coarse Grain Zone, CGZ）与(TiC+α'')相增强的TC4细晶区（Fine Grain Zone, FGZ）构成，其展现出优异的高强度与高塑性，性能优于纯TC4合金以及均质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，在强韧化效应中发挥了重要作用；而TC18粗晶与TC4细晶之间的晶粒协调变形，同样是实现优异塑性的核心原因。