新型高阻尼双相Mn-Cu合金的组织控制与阻尼机制研究

As a typical class of functional and structural materials, Mn-Cu alloys have attracted much attention and possessed broad application prospects because of their high damping capacity and excellent mechanical properties. Nevertheless, relatively lower operating temperatures and a narrower operating temperature range are significant barriers to applications of the alloys. Aiming at relatively higher operating temperatures and a broader operating temperature range, a novel duplex Mn-Cu alloy characterized by alternative distribution of Mn-rich phase and Mn-poor phase will be prepared by semi-solid solution treatment, and also duplex twinning structures will be regulated by semi-solid solution and aging treatment in this project. Spinodal decomposition structure, fractional martensite phase transformation and twinning structure of the Mn-Cu alloys with different duplex structures, as well as their variation will be investigated, and the effect of spinodal decomposition structure on the formation of twinning structure induced by fractional martensite phase transformation will be revealed. Variation of damping behavior with environmental factors will be explored for the Mn-Cu alloys with different duplex structures. Furthermore, their microscopic damping mechanism, especially the cooperative damping mechanism between duplex twinning structures will be revealed. Effects of different duplex structures on microhardness and tensile properties of the alloys will be studied, and also the reason for the change of mechanical properties caused by different duplex structures will be revealed. The research above can contribute to providing the theoretical and practical basis for the design, development and application of novel duplex Mn-Cu alloys with high damping capacity and their composites.

Mn-Cu合金具有高的阻尼性能和优良的力学性能，是一种具有广泛应用前景的减振降噪用功能结构材料。然而，其相对较低的使用温度及较窄的使用温域限制了该类合金的应用。本项目拟采取半固态固溶处理的方法制备一种高Mn相和低Mn相交替分布的双相Mn-Cu合金，并采用半固态固溶+时效工艺对双相的孪晶结构进行调控，使其在较高温度下及较宽温域内保持高阻尼态。研究在不同双相结构下，合金调幅分解组织、阶梯马氏体相变、孪晶结构的特征及其变化规律，揭示调幅分解组织对阶梯马氏体相变诱发孪晶形成的作用机理；研究在不同双相结构下，合金阻尼行为随环境因素的变化规律，揭示双相结构的阻尼产生机制，特别是双相的孪晶协同阻尼机制；研究不同双相结构对Mn-Cu合金显微硬度及拉伸性能的影响，揭示由不同双相结构引起的力学性能的变化机制。旨在通过以上研究，为该类新型高阻尼双相Mn-Cu合金及其复合材料的设计、开发与应用提供理论和实践依据。

Mn-Cu合金具有高的阻尼性能和优良的力学性能，已成为具有广泛应用前景的减振降噪用功能结构材料。然而，其相对较低的使用温度及较窄的使用温域在一定程度上限制了该类合金的应用。本项目采用半固态固溶处理的方法制备了一种富Mn相和贫Mn相交替分布的双相Mn-Cu合金，并通过改变半固态固溶温度及时效时间对其组织、阻尼性能和力学性能进行了调控和优化。具体地，采用真空感应熔炼法制备了Mn65-Cu23.75-Zn3-Al3-Ni3-Fe2-Ce0.05 (at.%)合金。对该合金进行轧制处理，然后进行均匀化退火。分别在850℃和950~1050℃对合金进行普通固溶及半固态固溶处理，随后在430℃时效0~16 h。研究了半固态固溶温度及时效时间对Mn-Cu合金组织、阻尼性能和力学性能的影响。结果表明：普通固溶合金组织由单一γ-MnCu相构成，而半固态固溶合金组织则由富Mn和贫Mn的γ-MnCu相构成，且随着半固态固溶温度的升高，贫Mn相的含量不断增加。合金阻尼性能随时效时间的延长呈现出先上升后下降趋势。在最优时效条件下，较低的半固态固溶温度可提高合金的阻尼性能，而较高的半固态固溶温度则会降低其阻尼性能。和普通固溶的S850合金相比，半固态固溶的S950合金强塑积提高了约70%。但随着半固态固溶温度的增加，合金强塑积又有所下降。本项目的研究可为该类新型高阻尼双相Mn-Cu合金及其复合材料的设计、开发与应用提供理论和实践依据。