等温挤压变形量对TiB+TiC增强钛基复合材料组织和室温力学性能的影响

Effects of Isothermal Extrusion Deformation on TiB + TiC Reinforced Titanium Matrix Composites and Room Temperature Mechanical Properties

塑性变形在提高原位自生非连续增强钛基复合材料(DRTMCs)强度的同时可改善塑性,但高的屈强比使其变形工艺非常敏感,压缩了适合变形的工艺区间,加大了变形加工难度。为此,提出了钛基复合材料(TMCs)等温挤压方法并成功制备出强塑性匹配较好的颗粒增强TMCs,研究了挤压变形量对其微观组织演化及综合性能变化规律的影响。结果表明,挤压过程中增强体TiB晶须和TiC颗粒断裂并实现二次分布,使TMCs中增强体分布得到合理有效控制,当挤压比从7增大到10时,TiB晶须长径比明显减小,但随后趋于稳定。随着变形量增加,α相内发生连续动态再结晶,形成与片层厚度相当的沿着原始片层呈竹节排布的细小等轴晶粒。从力学性能测试结果可知,在温度较低的两相区(985℃)进行等温热挤压变形,DRTMCs强度可达1 111 MPa,延伸率为15.7%,实现了较好的强塑性匹配。

The plasticity of in situ discontinuously reinforced titanium matrix composites(DRTMCs)was inevitably decreased due to the reinforcement when the most properties were improved.The deformation could simultaneously improve its strength and plasticity,but it was difficult to carry out for the high ratio of yield strength to tensile strength which made its deformation very sensitive to the processing.The strength and plasticity of in situ discontinuously reinforced titanium matrix composites(DRTMCs)could be improved by plastic deformation,but it was difficult to carry out for the deformation was very sensitive to the processing.So this study proposed an isothermal extrusion method,and titanium matrix composites were carried out successfully and the plasticity and strength of DRTMCs were improved simultaneously.The microstructure evolution and combination properties were studied as the extrusion ratio change.The results show that TiB whisker reinforcement and TiC particle are fractured and redistributed in the process of extrusion.Thus,the distribution of reinforcement is effective to be controlled.The TiB whisker aspect ratio decreases as the extrusion enlarged from 7 to 10.Then TiB aspect ratio tends to be stable with the increase of deformation.A fine equiaxed grain with a thickness equal to the thickness of the lamellae is formed in the original lamellae.The results of tensile tests show that the strength and elongation of DRTMCs processed at the temperature of 985℃are 1 111 MPa and 15.7%,respectively and they match well.