鈦鎳矽三元形狀記憶合金之研究

Studies on TiNiSi Ternary Shape Memory Alloys

李宗縉(Tsung-Ching Lee)

指導教授 ： 吳錫侃

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.00455

摘要

本文研究四種不同成分之富鈦及富鎳鈦鎳矽三元形狀記憶合金(SMAs)的析出物、變態行為及顯微組織等，並探討經過時效、熱循環及冷加工退火後之變態溫度的變化。Si之添加傾向替代Ni的原子位置，但其固溶性不佳，故在固溶處理後就有許多的第二相析出，富鎳鈦鎳矽SMAs之析出物為Ti5Ni4Si及Ti2Ni3Si，富鈦鈦鎳矽SMA中則有Ti2Ni及Ti5Si3。固溶處理後各鈦鎳矽SMAs均為B2↔B19’ 麻田散體變態，由EPMA及DSC結果可知，其變態溫度與基地成分之Ti/(Si+Ni) 比值有關，變態時之最大阻尼值可達0.098到0.162之間，皆為良好的制震材料。經熱循環100次導致變態溫度下降約10~20℃，唯仍維持B2↔B19’相變態，未有R相變態之產生。富鎳Ti48Ni50Si2 SMA經時效後，因Ti3Ni4在晶界及晶粒內部析出速率的不同，在300℃×72hr時效者出現B2→R(晶界附近)、B2→B19’(晶粒內部) 及R→B19’(晶界附近)的三階相變態；在400℃×120hr時效者在晶界附近和晶粒內部分別產生兩階之B2→R→B19’而有四階的相變態；而在650℃時效者，因析出物尺寸較大且有穩定態之TiNi3的析出，故成為一階的B2↔B19’相變態。Ti48Ni50Si2 SMA經時效處理後，Ti3Ni4析出物的大小及分布將影響到析出硬化的效果，其中經300℃×24hr時效者可達最大硬度422Hv，同時形狀回復率也提升至96.5%。經20%冷加工的Ti49Ni50Si1 SMA及40%冷加工的Ti49.5Ni50Si0.5 SMA在特定的時效溫度下，會有R相變態的產生，而使降溫時成為B2→R→B19’之二階相變態，此因析出物的整合應力場與冷加工後的殘留應力所共同造成的。

關鍵字

鈦鎳矽形狀記憶合金 ； 多階相變態 ； Ti3Ni4析出物 ； 時效處理 ； 制震能

並列摘要

In this study, four kinds of Ti-rich and Ni-rich TiNiSi ternary shape memory alloys (SMAs) are investigated for their precipitates, transformation behavior and microstructure. The effects of aging, thermal cycling and cold working on their transformation temperatures are also studied. The Si added in TiNi SMAs has a tendency to substitute for the Ni. But the solubility of Si in the TiNi matrix is low, which gives a significant TiNi-silicides precipitation. Four different TiNi-silicides are observed, in which Ti5Ni4Si and Ti2Ni3Si are formed in three Ni-rich TiNiSi SMAs, while Ti2Ni and Ti5Si3 are found in a Ti-rich TiNiSi SMA. The TiNiSi SMAs exhibit a B2↔B19’ transformation after solution treatment, and their transformation temperatures are related to the Ti/(Si+Ni) ratio in the matrix. The tanδ values of TiNiSi SMAs reach 0.098~0.162, which indicate that these SMAs exhibit excellent damping performance. Transformation temperatures of TiNiSi SMAs decrease 10~20℃ after 100 thermal cycling, but they still remain B2↔B19’. Due to different precipitation rates occurred at the grain boundaries and inside the grains, the Ni-rich Ti48Ni50Si2 SMA behaves a multi-stage transformation after 300~550℃ aging. Furthermore, the precipitation hardening of Ti48Ni50Si2 SMA depends on the size and distribution of Ti3Ni4 precipitates, and the maximum hardness of 422Hv is found after the SMA is aged at 300℃×24hr, in which the recovery can reach 96.5%. Under 350~650℃ aging temperature, the DSC results show the appearance of the R phase peak in 20% and 40% cold-rolled Ti49Ni50Si1 and Ti49.5Ni50Si0.5 SMAs, respectively, due to the coherent strain around precipitations and the existing residual strain after cold working.

並列關鍵字

TiNiSi SMAs ； Multi-stage phase transformation ； Ti3Ni4 precipitation ； TiNi silicides Aging/ Cold working ； Thermal cycling

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