Development and dental casting of the super-elastic alloy with superior biocompatibility

在所有形状记忆合金中，Ti-Ni合金具有上级的功能特性。然而，从该合金中少量溶解的镍（Ni）涉及生物相容性。本文研究了用第三元素Pd、Cu和Au替代Ni以降低具有形状记忆效应和超弹性的Ti-Ni合金中Ni离子的析出，结果表明，添加7.5%（质量分数）Pd的Ti-50.0Ni合金表现出柔性超弹性，与二元超弹性Ti-Ni合金相比，其表现出大约一半（0.2%）的表观屈服应力。随着Cu取代量的增加，合金的表观屈服应力和残余应变均降低。此外，Cu的加入还使二元形状记忆合金的超弹性范围增大。添加10%Cu的二元Ti-Ni合金是一种很有前途的体温超弹性合金，在310 K的1%乳酸浸泡试验中，Ni离子释放量较少。随着Au取代量的增加，相变温度降低到7%的Au添加量，并通过DSC测量在进一步添加中没有区别。49.4%Ti-Ni-4%Au和49.6%Ti-Ni-7%Au合金在体温下表现出超弹性。此外，向添加10%Cu的Ti-Ni合金中添加0.5质量%的Mo或Cr似乎是机械性能的极限，因为向合金中添加1.0质量%或更多的Mo或Cr显示脆性。

Ti-Ni alloy exhibits superior functional property among all shape memory alloys. Nevertheless, a small amount of dissolution of nickel (Ni) from this alloy concerns biocompatibility. In this study, the substitution of the third elements such as palladium (Pd), copper (Cu) and gold (Au), for Ni was investigated to decrease Ni ion release from Ti-Ni alloy which possesses shape memory effect and super-elasticity.Pd addition of 7.5% (mass%) to Ti-50.0Ni alloy showed flexible super-elasticity, which exhibited approximately a half apparent (0.2%) proof stress comparing with the binary super-elastic Ti-Ni alloy. With the increase of Cu substitution, both the lower apparent proof stress and residual strain were observed. Moreover, enlarged content of super-elastic range was obtained by Cu addition to binary shape memory Ti-Ni alloy. 10% Cu addition of binary Ti-Ni alloy was promising composition of super-elasticity at body temperature, and exhibited less Ni ion release in the result of immersion test of the 1% lactic acid at 310K. With the increase of Au substitution, transformation temperatures decreased up to the 7% Au addition and indistinguishable in the further addition by DSC measurement. 49.4%Ti-Ni-4%Au and 49.6%Ti-Ni-7%Au alloy were proved to show super-elasticity at body temperature. Furthermore, 0.5 mass% Mo or Cr addition to the 10% Cu added Ti-Ni alloy seemed the limit in relation to mechanical properties since 1.0 mass% or more addition of Mo or Cr to the alloy showed brittleness.