(TiHfTa)_(50)(NiCu)_(50)高熵记忆合金的组织与性能

Microstructure and properties of (TiHfTa)_(50)(NiCu)_(50) high entropy shape memory alloy

采用真空电弧熔炼制备了(Ti_(40-x)Hf_(10)Ta_(x))_(50)(NiCu)_(50)(x=0、1、5和10,at%)高熵记忆合金,通过扫描电镜(SEM)、X射线衍射(XRD)和室温循环压缩等研究了Ta含量与加载条件等对合金显微组织、力学性能、超弹性与稳定性等的影响。结果表明:铸态(Ti_(40-x)Hf_(10)Ta_(x))_(50)(NiCu)_(50)高熵记忆合金兼具优良的力学性能与超弹性,与现有2~4元Ti基记忆合金相比拥有较高的输出功;在预应变为15%时,Ta0、Ta1和Ta5合金的施加应力为1390.8、1591.2和2101.7 MPa,输出功为100.2、124.3和197.4 J/cm^(3)。随Ta含量的增加,合金断裂强度和伸长率下降,但Ta1和Ta5合金的屈服强度与可回复应变增加,最大可回复应变分别为7.8%和9.4%,其中超弹性应变分别为4.0%和4.4%,加热后总可回复应变分别达到10.1%和10.6%。在应变递增的循环压缩过程中,合金的可回复应变、超弹性应变等随着应变的增加逐渐增大,循环后期增速减小,而在应变为固定值的循环压缩过程中,经5~6次循环后,合金的回复率可达100%,超弹性、应力滞后、输出功等趋于稳定。

High entropy shape memory alloys of(Ti_(40-x)Hf_(10)Ta_(x))_(50)(NiCu)_(50)(x=0,1,5 and 10,at%)were prepared by vacuum arc melting.The effects of Ta content and loading conditions on microstructure,mechanical properties,superelasticity and stability of the alloys were studied by means of scanning electron microscopy(SEM),X-ray diffraction(XRD)and room temperature cyclic compression.The results show that the as cast(Ti_(40-x)Hf_(10)Ta_(x))_(50)(NiCu)_(50) high entropy memory alloys have excellent mechanical properties and superelasticity,and have higher output work compared to existing 2-4 element Ti-based memory alloys.When the pre strain is 15%,the applied stress of the Ta0,Ta1,and Ta5 alloys is 1390.8,1591.2,and 2101.7 MPa,and the output work is 100.2,124.3,and 197.4 J/cm^(3).With the increase of Ta content,the fracture strength and elongation of the alloys decrease,but the yield strength and recoverable strain of the Ta1 and Ta5 alloys increase,with the maximum recoverable strain of 7.8% and 9.4% respectively and the superelastic strain of 4.0% and 4.4%respectively.After heating,the total recoverable strain of the Ta1 and Ta5 alloys reaches 10.1% and 10.6%,respectively.In the cyclic compression process with increasing strain,the recoverable strain and superelastic strain of the alloys gradually increase with the increase of strain,and the growth rate decreases in the later period of the cycle.However,in the cyclic compression process with fixed strain,after 5-6 cycles,the recovery rate of the alloys can reach 100%,and the superelasticity,stress hysteresis and output work tend to be stable.