Mg/NiTi复合材料的制备及阻尼性能

采用Mg粉的无压熔渗法制备Mg/NiTi复合材料以提高多孔NiTi合金的强度和阻尼性能。通过OM、SEM、EDS和XRD分析Mg/NiTi复合材料的显微组织结构，采用压缩实验分析其抗压强度、吸能能力，采用热机械分析仪分析其内耗和存储模量。结果表明：经Mg粉无压熔渗后，多孔NiTi合金的孔隙被Mg填充，其孔隙率由原来的50.38%下降至5.6%，且Mg与NiTi合金的界面结合良好。多孔NiTi合金主要由B2奥氏体相和B19'马氏体相及少量Ni₃Ti相和NiTi₂相组成；Mg/NiTi复合材料除增加了熔渗的Mg相外，还新生成了Mg₂Ni相。Mg的渗入未改变多孔NiTi合金相变行为，但提高了相变温度。Mg/NiTi复合材料的抗压强度可达554 MPa，较多孔NiTi合金提高了61%，压缩断裂方式也由多孔NiTi合金的孔壁崩塌断裂转变为Mg/NiTi复合材料的剪切断裂。Mg/NiTi复合材料的吸能较多孔NiTi合金有大幅提高。同时，Mg/NiTi复合材料的内耗值有所增加，而存储模量大幅提高，整体呈现出更佳的阻尼性能。

Preparation and damping capacity of Mg/NiTi composites

The Mg/NiTi composites were prepared by pressureless infiltration of Mg powders to improve the strength and damping capacity of porous NiTi alloys. The microstructure of the Mg/NiTi composites were investiaged by OM, SEM, EDS and XRD, the compressive strength and energy absorption ability were analyzed by compressive test and the internal friction and storage modulus were tested by the thermal mechanical analyzer. The results show that the pores of the porous NiTi alloy are filled by Mg through the pressureless infiltration of Mg powders, and the porosity decreases from 50.38% to 5.6% for Mg/NiTi composites. Moreover, the interface bonding of Mg and NiTi alloy is good. The porous NiTi alloys are mainly composed of B2 austenite phase and B19' martensite phase with a few Ni₃Ti and NiTi₂ phases, while the Mg/NiTi composites are composed of infiltrated Mg phase and newly generated Mg₂Ni phase except the phases contained in the porous NiTi alloys. The transformation behavior of the porous NiTi alloys does not change but the transformation temperatures increase after the infiltration of Mg. The compressive strength of the Mg/NiTi composites is up to 554 MPa, 61% higher than that of the porous NiTi alloys. The compression fracture mode also changes from the pore wall collapsed fracture of the porous NiTi alloy to the shear fracture of the Mg/NiTi composites. The energy absorption ability of the Mg/NiTi is greatly improved compared to the porous NiTi alloys. At the same time, the internal friction value of Mg/NiTi composites has a little increase, while the storage modulus is significantly improved, presenting much better damping capacity.