矫直温度对Ti-50.8Ni超弹性合金丝材相变行为及力学性能的影响

Effects of straightening temperature on transformation behavior and mechanical properties of Ti-50. 8Ni superelastic alloy wire

采用示差扫描量热仪(DSC)、拉伸试验及透射电镜研究了不同矫直温度对Ti-50.8Ni超弹性合金丝材相变特性、超弹性及微观结构的影响。结果表明,冷矫态合金丝材冷却/加热时的相变类型为A→M/M→A,而温矫态及热矫态合金丝材冷却/加热时发生A→R→M/M→A(A―母相,R―R相,M―马氏体)型相变;冷矫态合金丝材组织择优取向性强,位错密度高,亚晶界弯曲模糊;而热矫态合金丝材缺陷密度最低,亚晶界平直清晰,超弹性最好。分析认为,应力、位错密度对Ti-50.8Ni超弹性合金丝材的相变特性及超弹性有重要的影响。

Effects of different straightening temperature on transformation characteristics,superelastic property and microstructure of Ti-50. 8Ni alloy wire were investigated with DSC,tensile test and TEM,respectively. The results show that the phase transformation of cold straightened alloy is A→M / M→A during cooling / heating process,and the phase transformation of warm and hot straightened alloy are A→R→M / M→A( A-parent phase,R-R phase,M-martensite phase) during cooling / heating process. The microstructure of the cold straightened alloy shows strongly preferred orientation,high dislocation density,bended and fuzzily subboundary,while the hot straightened alloy shows minimum defect density,straight and clear subboundary and best superelastic property. Stress and dislocation density great influence the transformation characteristics and superelastic property of the alloy.