Ge元素的添加对Co-V-Si高温形状记忆合金的组织和热稳定性能的影响

Effects of Ge addition on the microstructure and thermal stability of Co-V-Si high-temperature shape memory alloys

摘要:

本文对Co₆₄V₁₆Si₂₀形状记忆合金中的硅元素用锗元素取代进行了研究。系统研究了Co₆₄V₁₆Si_20-xGe_x (x = 2,4,6,8, at. %)系列合金在热循环过程中的组织、马氏体转变、热循环稳定性和微观结构演化。当x = 2时,合金为具有D0₂₂结构的单相马氏体组织。随着Ge含量增加到4 at. %和6 at. %,观察到(αCo)相和D0₂₂马氏体相的两相组织。当Ge含量达到8 at. %时,合金呈现(αCo)相 + D0₂₂马氏体相+ R相的三相组织。结果表明,与Co₆₄V₁₆Si₂₀基体合金相比,加入锗元素进行合金化可使可逆马氏体转变温度提高近50℃。虽然在热循环过程中伴随着(αCo)相或R相的析出,但是可逆马氏体相变峰仍然出现在十次热循环中。结果表明,锗元素的添加可以改善Co-V-Si高温形状记忆合金的热循环稳定性。

Abstract:

A study of the Ge substitution for Si in the Co₆₄V₁₆Si₂₀ shape memory alloy was performed in this work. The microstructure, martensitic transformation, thermal cycle stability, microstructural evolution during thermal cycling of the Co₆₄V₁₆Si_20-xGe_x (x = 2, 4, 6, 8, at. %) alloys were studied. When x = 2, the alloy is single D0₂₂ martensite. With increasing Ge content to 4 and 6 at. %, two-phase microstructure of (αCo) + D0₂₂ martensite was observed. When Ge content is up to 8 at. %, three-phase microstructure of (αCo) + D0₂₂ martensite + R phase was observed. The results show that the reversible martensitic transformation temperatures increased by nearly 50°C through adding Ge comparing with that of the Co₆₄V₁₆Si₂₀ matrix alloy. Although the (αCo) or R phases precipitated during thermal cycling process, the reversible martensitic transformation peaks were observed during ten times thermal cycles. It reveals that the Ge addition can improve thermal cycling stability of Co-V-Si high-temperature shape memory alloy.