【正文】 四川大學(xué)碩士學(xué)位論文 I 熱處理工藝對 Mn20Cu5Ni2Fe 阻尼合金 組織和性能的影響 材料加工工程專業(yè) 研究生 傅 旭 指導(dǎo)教師 李 寧教授 隨著現(xiàn)代科技工業(yè)的高速發(fā)展，以及人類對生活環(huán)境要求的不斷提高，減振降噪成為亟待解決的問題，而阻尼合金由于其獨特性能在減振降噪領(lǐng)域得到了越來越廣泛的應(yīng)用。 MnCu 合金屬于孿晶型高阻尼合金，該合金兼具了較高的力學(xué)性能和阻尼性能，因此得到了國內(nèi)外學(xué)者的廣泛關(guān)注。本文采用 JN1型倒扭擺儀、光學(xué)顯微鏡、 XRD 和 TEM 等測試分析方法研究了熱處理工藝對Mn20Cu5Ni2Fe 合金組織和性能的影響。從材料的組織和性能之間的關(guān)系出發(fā)，主要探討了以下三個方面的內(nèi)容： 時效處理對 Mn20Cu5Ni2Fe 合金阻尼性能的影響； 時效處理對 Mn20Cu5Ni2Fe 合金力學(xué)性能的影響； 形變熱處理對 Mn20Cu5Ni2Fe 合金阻尼性能的影響。通過分析得到了如下結(jié)論： 合金阻尼性能對時效溫度和時效時間敏感。 Mn20Cu5Ni2Fe 合金獲得阻尼性能的溫度區(qū)間為 400℃ ~500℃。在不同溫度下時效 4h 后，阻尼性能與時效溫度較好的滿足拋物線關(guān)系。在時效時間為 4h 時，合金在 435℃達(dá)到最大阻尼性能（ δ=）。時效溫度越高，合金達(dá)到阻尼峰值的時間就越短，但此時合金的阻尼峰值反而降低。隨時效時間的增加，阻尼性能先增加然后又緩慢降低。 孿晶結(jié)構(gòu)是 MnCu 合金具有高阻尼性能的原因，而調(diào)幅分解是導(dǎo)致 MnCu合金產(chǎn)生孿晶結(jié)構(gòu)的前提。在 400~500℃保溫， MnCu 合金會發(fā)生 調(diào)幅分解，該分解使低 Mn 含量的 MnCu 合金形成富 Mn 區(qū)，隨著時效時間的增加，富 Mn區(qū)長大，富 Mn 區(qū)的最大 Mn 含量與時效溫度有關(guān)，時效溫度升高該含量降低。四川大學(xué)碩士學(xué)位論文 II 富 Mn 區(qū)的形成使合金的相變點升高，在冷卻至室溫過程中發(fā)生反鐵磁轉(zhuǎn)變和fccfct 轉(zhuǎn)變。通過應(yīng)變釋放機(jī)制，晶格發(fā)生一定程度的畸變，形成孿晶結(jié)構(gòu)。合金過時效會在孿晶界面形成位錯網(wǎng)絡(luò)阻礙孿晶界面的滑移，因此阻尼性能降低。 合金的 強(qiáng)度和硬度隨時效溫度的升高和時效時間的增加而升高，而延伸率相應(yīng)降低。 合金強(qiáng)度隨時效時間的增加可分為兩個階段，當(dāng)時效時間小于 4h時，合金的 強(qiáng)度迅速上升，而時效時間繼續(xù)增加，強(qiáng)度增加的幅度降低。孿晶結(jié)構(gòu)和調(diào)幅組織是 Mn20Cu5Ni2Fe 合金力學(xué)性能變化的原因。調(diào)幅組織通過兩相區(qū)共格應(yīng)力場而使合金得到強(qiáng)化；孿晶界面對位錯的滑移有阻礙作用，因此孿晶密度升高也會使合金的力學(xué)性能升高。 形變會使 Mn20Cu5Ni2Fe 合金阻尼性能顯著降低。合金阻尼性能隨形變量的增加而迅速降低，當(dāng)形變量大于 2%時，合金的阻尼性能已顯著降低。 形變過程引入的位錯對孿晶界面的釘扎作用是合金阻尼降低的主要原因 。形變后在 435℃保溫會使位錯應(yīng)力場消失或部分消失從而使 形變后的合金阻尼性能得到一定程度的回復(fù)。當(dāng)形變量較小時孿晶帶變細(xì)并發(fā)生重排，此時回復(fù)處理能使合金阻尼性能完全回復(fù)；隨著形變增加，孿晶結(jié)構(gòu)遭到破壞，回復(fù)處理只能使合金的阻尼性能得到部分回復(fù)。 關(guān)鍵詞： MnCu阻尼合金； 時效； 孿晶界面；調(diào)幅分解； fccfct 轉(zhuǎn)變；形變及回復(fù) 四川大學(xué)碩士學(xué)位論文 III Effect of heat treatment on microstructures and properties in Mn20Cu5Ni2Fe damping alloy Major: Materials Processing Engineering Postgraduate: Fu Xu Supervisor: Prof. Li Ning With the rapid development of modern industries and the pursuit of high quality of life, reducing vibration and noise has bee an important issue that must to be solved. Damping materials, because of its unique properties of vibration reducing, have been widely used in reducing vibration and noise. MnCu alloy, a twinning type of high damping materials, shows a bination of good strength and high damping capacity and has attracted extensive attention. In the present paper, JN1 inverse torsion pendulum, optical microscope, XRay diffraction (XRD) and transmission electron microscope (TEM) were carried out to study for the relationship between microstructures and properties in Mn73Cu20 Ni5Fe5 alloy. We considered three aspects: 1, the effects of aging treatment on damping properties in Mn20Cu5Ni2Fe alloy。 2, the effects of aging treatment on mechanical properties in Mn20Cu5Ni2Fe alloy。 3, the effects of thermomechanical treatment on damping properties in Mn73Cu20 Ni5Fe5 alloy. From these studies, we can conclude that: The damping capacity of Mn20Cu5Ni2Fe alloy is sensitive to aging temperature and time. The spinodal deposition temperature of Mn20Cu5Ni 2Fe alloy ranges from 400℃ to 500℃ . When Mn20Cu5Ni2Fe alloy is aged for 四川大學(xué)碩士學(xué)位論文 IV 4h, the damping capacity of alloy shows a parabolic relationship with aging temperature, and at this time peak damping capacity (δ=) is obtained at 435℃ . With a higher aging temperature, a shorter aging time was used to reach damping peak, but a lower peak damping capacity was obtained. With increasing aging time, damping capacity first increase and then decrease. The damping capacity of MnCu alloy originates from the slip of twinning structures, while the twinning structures are attributed to the spinodal deposition of MnCu alloy. Spinodal deposition occurred, which lead to the formation of Mnrich region, when MnCu alloy was aged at 400~500℃ . With increasing aging time, Mnrich regions grow and the phase transformation points increase, which result in antiferromagic transformation and fccfct transformation. According to the strain release mechanism, lattice is changed and twinning structures are formed. When MnCu alloy is overaged, dislocations are formed between twinning boundaries and result in decrement of damping capacity. The strength and hardness increase with aging temperature and aging time, and elongation decrease correspondingly. Strength behavior with increment of aging time can be divided into two stages: I) the strength increases rapidly when aging time is shorter than 4h。 II) the strength increases in a slow and stable rate when aging time is longer than 4h. The changes of strength of Mn20Cu5Ni2Fe alloy is attributed to spinodal structures and twinning structures. Spinodal structures strengthen alloy by the coherent stress field between the separated phases. Twinning boundaries act as a barrier of dislocations and result in the increase of strength. Deformations result in the dramatic decrease of damping capacity of Mn20Cu 5Ni2Fe alloy. The damping capacity decreases with the increment of deformations, and the damping capacity is much lower when the deformation rate is higher than 2%. The decrease of damping capacity is mainly attributed to the formation of dislocations when the deformations are applied, which retard the slip of twinning boundaries. Retreatment (aging at 435℃ ) can make stress field of dislocations disappeared fully or partly, and thus the damping capacity can be restored fully or partly after retreatment. When deformation rate is small, the twinning structures 四川大學(xué)碩士學(xué)位論文 V bee nicked and rearrangement, and at this case the damping capacity can be restored pletely. While when the deformation rate is relatively higher, the twinning structures are changed dramatically and thus the damping capacity only can be restored partly. Keywords: MnCu damping alloy。 aging treatment。 twinning boundaries。 spinodal deposition。 fccfct transformation。 deformation and retreatment. 四川大學(xué)碩士學(xué)位論文 VI 目錄 熱處理工藝對 Mn20Cu5Ni2