Ni含量和第三元素对退火态钛镍合金相变的影响

Phase Transformation of Annealed Ti Ni Shape Memory Alloy Affected by Ni Concentration and Third Alloying Elements

采用差示扫描量热仪（DSC）分析了不同镍含量（49.7%,50.0%,50.5%,50.8%,50.9%;原子分数）及加入第三元素（Fe,Cu）的退火态钛镍合金的相变特征。结果表明：当Ni含量在49.7%~50.9%范围内变化时,退火态二元钛镍合金相变只存在B2B19＇一阶段相变。加入3%Fe元素后,其退火态相变类型为B19＇RB2二阶段相变。加入5%Cu元素后,其退火态相变类型与二元钛镍合金相似,只出现B2B19＇一阶段相变。对于二元钛镍合金,其各相变温度随着镍含量的增加近似呈线性降低,相变滞后ΔTp随着镍含量的增加而减小,相变滞后ΔTs随着镍含量的增加先增大再减小。马氏体相变峰宽ΔTM和逆马氏体相变峰宽ΔTA在Ni含量为50.2%~50.4%时取得最小值。退火态二元钛镍合金的相变潜热ΔH随着镍含量的增加而下降。加入3%Fe元素的钛镍合金,其相变潜热ΔH为3~5 J·g-1,相转变更易进行。加入5%Cu元素的钛镍合金的相变潜热ΔH与等原子比二元钛镍合金相当,其相变峰宽ΔTM和ΔTA皆低于二元钛镍合金,相变滞后ΔTs和ΔTp更小,分别可达到8.5和24.3℃,更适合制作高精度、快响应热驱动系统。

Differential scanning calorimetry （DSC） was used to analyze the phase transformation characteristic of fully annealed TiNi alloy with different nickel contents （49.7% , 50.0% , 50.5% , 50.8% , 50.9% ; atom fraction） and Fe and Cu element. The results indicated when the nickel content changed from 49.7% to 50.9% , there only existed the first stage martensitic transformation and its reverse transformation （B2＇←→B19＇）. The phase transformation type of the annealed TiNi alloy with 3 % Fe was B19＇←→R←→B2 two stage transformation. The phase transformation of TiNi alloy with 5% Cu was similar to that of the binary TiNi alloy, for which there only existed B2←→B19＇ phase transformation. For binary TiNi alloys, the phase transformation temperatures decreased linearly with the increase of nickel content. The hysteresis of phase transformation △Tp, decreased with the increase of nickel content, and the hysteresis of phase transformation △Ts increased in low Ni content range, then decreased in high Ni content range. The minimum of peak width ATM and ATA lay in the range of 50.2%- 50.4%. The latent heat of phase transformation decreased with the increase of nickel content. The latent heat AH of the annealed TiNi alloy with 3% Fe was about 3 - 5 J·g^-1, which indicated the phase transformation was easier to go on. The latent heat of the annealed TiNi alloy with 5% Cu amounted to that of the equatomic binary TiNi alloys. The phase transformation peak width △TM and ATA were both lower than those of the binary TiNi alloys, and the hysteresis of phase transformation△Tp and ATs was narrow, which could reach 24.3 and 8.5 ℃ , respectively. Therefore, it was more suitable for production of high accuracy, fast response thermal drive systems.