预变形与等温时效耦合作用下Ti-10Mo-1Fe/3Fe层状合金的力学性能

Coupling Effect of Pre-Strain Combined with Isothermal Ageing on Mechanical Properties in a Multilayered Ti-10Mo-1Fe/3Fe Alloy

基于热锻/热轧工艺以及均匀化热处理制备了孪生与位错滑移耦合变形的Ti-10Mo-1Fe/3Fe层状合金,利用LSCM、XRD、SEM、SEM-EDS、EBSD、Vickers硬度计和拉伸试验机等研究了预变形与等温时效耦合作用对层状合金力学性能的影响。结果表明,经拉伸预变形和等温时效处理后,该合金具有{332}<113>孪晶和位错滑移带多层交替变形组织,且呈现出较高的屈服强度和较大的均匀伸长率。等温时效析出的ω相提高了β相稳定性,使得变形初期的塑性变形方式由位错滑移主导,这是其具有较高屈服强度的主要原因。预变形诱发的孪晶推迟了屈服之后颈缩的快速发生,而且后续变形过程中进一步激活的孪晶引起的动态晶粒细化效应及其与层界面的交互作用,使其具有较大的均匀伸长率。因此,在孪生与位错滑移耦合变形层状合金的基础上,进一步通过预变形诱发{332}<113>孪晶和等温时效析出ω相的双重耦合效应,可在较大范围内调控β型钛合金的强塑性匹配。

Owing to their low density,high specific strength,biocompatibility,and good corrosion resistance,titanium and its alloys have been widely used in the aerospace,biomedical,and marine engineering fields.As engineering applications of titanium alloys continue to develop,especially in special engineering projects,the service safety and stability of titanium alloys must be satisfied under extremely complex conditions.Unfortunately,traditional titanium alloys usually exhibit low plastic-deformation ability and no significant work hardening behavior,which limits their applicability.Improving both the strength and ductility of these materials is expected to broaden their engineering applications.In recent years,β-type(body-centered cubic)titanium alloys have shown good formability and impact toughness,by virtue of their diverse plastic deformation modes and excellent ageing strengthening.Therefore,they are promising candidates for titanium alloys with a good strength-ductility combination.In this work,a multilayered Ti-10Mo-1Fe/3Fe alloy was manufactured by a multi-pass hot rolling and heat treatment,and the coupling effects of pre-strain and isothermal ageing on the mechanical properties of the alloy were studied by various techniques:laser scanning confocal microscopy,XRD,SEM,SEM-EDS,EBSD,a Vickers hardness tester,and a tensile testing machine.After pre-strain and isothermal ageing,the alloy exhibited{332}<113>twins and slip bands alternately multilayered deformation microstructures.The alloy demonstrated a relatively high yield strength and large uniform elongation.The high yield strength resulted from the initial plastic deformation,which was dominated by dislocation slips due to isothermalω-phase precipitation.The early onset of plastic instability after yielding was hindered by the pre-strain induced twins,and the uniform elongation was enhanced not only by the dynamic Hall-Petch effect caused by further twinning activation,but also by interactions between the twin and layer-interface.As demonstrated on this multilayered alloy with twinning and dislocation-slip coupled deformation,the strength-ductility combination inβ-type titanium alloys can be controlled through the coupling effect of pre-strain induced{332}<113>twins and the subsequently precipitatedωphase.