Ti基非晶复合材料的强韧化机理

Strengthening and Toughening Mechanism of Ti-based Metallic Glass Composites

采用水冷铜坩埚磁悬浮熔炼-铜模吸铸法在真空及高纯氩气保护条件下制备了直径3 mm的(Ti0.5Ni0.48M0.02)80Cu20(M=Fe,Ce,Zr)合金,研究了Fe、Ce、Zr对合金凝固组织中形状记忆晶相析出的变化规律的影响,分析了该合金的室温力学行为与强韧化机理。研究发现,(Ti0.5Ni0.48M0.02)80Cu20(M=Fe,Ce,Zr)合金铸态结构均为非晶+形状记忆晶相(B2过冷奥氏体和B19’热致马氏体)的复合结构,其中M=Fe、Ce的合金B2相析出体积分数较多,M=Zr的合金B19’相析出体积分数较多。在室温压缩过程中,合金均表现出良好的综合力学性能,其中以M=Ce的合金性能最优,断裂强度,屈服强度,塑性应变分别达到2645 MPa,1150 MPa和12.2%。合金在受压应力断裂后,组织中奥氏体相体积分数减小,马氏体相体积分数增加,同时在屈服后均表现出强烈的加工硬化行为。加工硬化速率和瞬时加工硬化指数随真应变的变化分为3个阶段,合金内部在压应力的作用下B2向B19’相转变是合金强韧化的主要动力。M=Fe的合金加工硬化速率、平均加工硬化指数、瞬时加工硬化指数最大,加工硬化能力最强,M=Ce的合金次之,M=Zr的合金最弱。

Ti0.5Ni0.48M0.02)80Cu20(M=Fe,Ce and Zr)alloy with 3 mm in diameter was fabricated by suspend melting under argon atmosphere using a water-cooled Cu mold.The influences of Fe,Ce and Zr on the shape-memory crystalline phase precipitation law in the solidification structure of alloys were studied,and the mechanical behaviors at room temperature and strengthening and toughening mechanism of alloys were analyzed as well.The results show that the as-cast microstructure of(Ti0.5Ni0.48M0.02)80Cu20(M=Fe,Ce and Zr)alloys is the amorphous matrix and shape-memory crystal phase(B2 undercooled austenite and B19’thermal martensite)structure.More B2 phase precipitates in M=Fe,Ce alloy.In M=Zr alloy,more B19’phase precipitates.The alloys all exhibit good comprehensive mechanical properties,among which M=Ce alloy has the best comprehensive mechanical properties,and the fracture strength,yield strength and plastic strain are 2645 MPa,1150 MPa and 12.2%,respectively.After alloys fracture with loading,the B2 austenitic phase volume fraction decreases and B19’martensite increases.Moreover,the room temperature deformation behavior of alloys can be described as elastic deformation and strong work hardening after yielding.The work hardening rate and instantaneous work hardening exponent are divided into three stages with the change of true strain,and the transformation of B2 to B19’under the compressive stress is the main driven force of alloy strengthening and toughening.The work hardening rate,work hardening exponent and instantaneous work hardening index of the M=Fe alloy are the largest and its work hardening ability is the strongest,while the work hardening ability of M=Ce alloy is weaker than M=Fe alloy,and that of M=Zr alloy is the weakest.