本文選題：Cu-Ni-Mn系合金　切入點：不連續(xù)析出反應　出處：《北京有色金屬研究總院》2016年博士論文

【摘要】：Cu-20Ni-20Mn合金是一種典型的高強高彈無鈹銅合金,具有與鈹青銅相當彈性模量和強度,其高溫穩(wěn)定性優(yōu)于鈹青銅,是一種潛在的鈹青銅替代材料。迄今,已有研究通過Cu-Ni-Mn系合金熱力學相圖和組織觀察,初步闡明了Cu-20Ni-20Mn合金的時效析出行為。為更系統(tǒng)的研究時效過程中Cu-20Ni-20Mn合金的組織演變規(guī)律及其強化機制,本文利用金相與電子顯微技術,X射線衍射等分析方法對Cu-20Ni-20Mn合金組織結(jié)構(gòu)進行了觀察;采用拉伸、沖擊和摩擦等性能測試手段測量合金的力學性能。通過分析微觀組織結(jié)構(gòu)與力學性能之間的內(nèi)在關系,構(gòu)建合金微觀組織結(jié)構(gòu)-強化機制-力學性能間的映射關系,并探索Cu-20Ni-20Mn合金在不同服役條件下微結(jié)構(gòu)特征對綜合力學性能的調(diào)控機制。Cu-20Ni-20Mn合金中會發(fā)生三種固態(tài)相變反應,即不連續(xù)析出反應,連續(xù)析出反應,以及沉淀相的回溶反應。使用金相顯微鏡(OM)、掃描電子顯微鏡(SEM),觀察各溫度區(qū)間Cu-20Ni-20Mn合金的微觀組織演變,結(jié)合DSC曲線分析合金升溫過程中的熱力學變化,以確定合金的固態(tài)相變反應溫度。合金不連續(xù)析出反應發(fā)生的溫度范圍為200℃-475℃;連續(xù)析出反應發(fā)生的溫度范圍為350℃-475℃;合金固溶線溫度在500℃至525℃之間。在不連續(xù)析出反應過程中,在晶界處形核析出由片層狀NiMn相與貧溶質(zhì)原子基體組成的不連續(xù)析出組織,由于合金中較高強度不連續(xù)析出組織,合金強度能明顯提高;發(fā)生連續(xù)析出反應時,NiMn相顆粒在基體中彌散析出,由于彌散強化的作用能有效提高合金強度。在350℃(不連續(xù)析出反應為主導)和450℃(連續(xù)析出反應為主導)時效的峰值硬度分別為451Hv和436Hv,這說明兩種時效析出反應能夠通過不同的強化方式提高合金強度,二者的強化效果大致相同。通過TEM分析可以確定時效過程中析出的沉淀相是有序的面心四方結(jié)構(gòu)NiMn相,NiMn相與基體存在一定的晶體學取向關系,具體的取向關系為:(002)matrix∥(001)NiMn,[100]matrix∥[100]NiMn。不連續(xù)析出組織的長大速率與溫度有關。通過JMAK方程和Aaronson-Liu模型描述Cu-20Ni-20Mn合金的不連續(xù)析出長大動力學過程,得出不連續(xù)析出組織的晶界化學擴散激活能分別為72.7±7.2 kJ/mol和94.1±16.8 kJ/mol,遠小于Ni、Mn元素在基體中發(fā)生體擴散所需的激活能。這說明不連續(xù)析出組織易于在晶界出形核析出,這也是不連續(xù)析出反應的溫度區(qū)間要大于連續(xù)析出反應的原因。不連續(xù)析出反應與連續(xù)析出反應存在競爭關系,彌散析出的NiMn相會抑制不連續(xù)析出組織的長大,不連續(xù)析出組織也可能會吞噬尺寸較小的NiMn相粒子。通過TEM和小角X射線散射分析可以確定,當NiMn相尺寸大于5nm,能夠有效阻礙不連續(xù)析出組織界面前沿的遷移。冷變形將導致合金中的位錯密度增加,這不僅能促進NiMn相的沉淀析出,還能提高合金強度。固溶態(tài)合金經(jīng)過變形量為95%的冷軋后,其屈服強度達到807Mpa。然而隨著NiMn相的彌散析出,位錯強化效果逐漸減弱,沉淀強化將起到主導作用。合金晶粒尺寸減小可以增強晶界強化的效果,從而提高合金屈服強度。通過對比晶粒尺寸與合金力學性能的關系,可以確定Cu-20Ni-20Mn合金晶粒直徑與硬度符合Hall-Petch關系相符,其Hall-Petch方程可以表示為Hv=82.6+0.28D-1/2。根據(jù)Cu-20Ni-20Mn合金的潛在應用環(huán)境,對合金的沖擊性能、摩擦性能以及低溫性能進行了研究。研究發(fā)現(xiàn),當溫度為77K,Cu-20Ni-20Mn合金的強度和彈性模量會略微升高。通過強度比與彈性模量比可知材料強度主要是受到非熱障礙控制的。深冷處理前后,材料晶格常數(shù)沒有變化,性能較為穩(wěn)定。合金的沖擊吸收功所隨時效時間的延長逐漸的減小。低溫條件下和深冷處理后,合金的沖擊性能差別不大。以石墨作為摩擦副,與不同時效狀態(tài)下的Cu-20Ni-20Mn合金材料進行摩擦,其摩擦系數(shù)是恒定的,約為0.09。
[Abstract]:Cu-20Ni-20Mn alloy is a typical high strength and high modulus without beryllium copper alloy, beryllium bronze with quite elastic modulus and strength, its high temperature stability is better than that of beryllium bronze, beryllium bronze is a potential substitute material. So far, the existing research by Cu-Ni-Mn alloy phase diagram and tissue observation, illustrates the precipitation behavior of Cu-20Ni-20Mn alloy for Cu-20Ni-20Mn alloy on the aging process more systematic in microstructure evolution and strengthening mechanism, using metallography and electron microscopy, X ray diffraction analysis method was employed to observe the microstructure of Cu-20Ni-20Mn alloys; mechanical properties by tensile, impact and friction performance test means to measure the alloy. By analyzing the relationship between the microstructure and Mechanical properties of the alloy, construct the micro structure and mechanical properties of the strengthening mechanism of the relationship between, and. Cable of Cu-20Ni-20Mn alloy under different service three kinds of solid phase reaction control mechanism of.Cu-20Ni-20Mn alloy on mechanical properties under the condition of micro structure, namely the discontinuous precipitation reaction, continuous precipitation reaction, and precipitate dissolution reaction. Using optical microscope (OM), scanning electron microscopy (SEM), microstructure evolution the temperature range of Cu-20Ni-20Mn alloy, thermodynamic changes curve analysis combined with DSC alloy during heating, in order to determine the solid phase reaction temperature. The temperature range of alloy alloy discontinuous precipitation reaction is 200 -475 DEG C; temperature range for continuous precipitation reaction 350 -475 DEG C; alloy solid solution temperature in line 500 degrees centigrade to 525 degrees centigrade. The discontinuous precipitation reaction process, composed of lamellar NiMn and depleted solute atoms in the grain boundary of matrix nucleation precipitation of discontinuous precipitation by the organization. In the alloy with high strength discontinuous precipitation, the strength of the alloy can significantly improve; continuous precipitation reaction, the NiMn particles dispersed in the matrix precipitate, due to dispersion strengthening effect can effectively improve the strength of the alloy. At 350 DEG C (discontinuous precipitation reaction led) and 450 degrees (continuous precipitation reaction as the dominant peak) the hardness of aging were 451Hv and 436Hv, indicating that the two kinds of aging precipitation reaction can improve the strength of the alloy by strengthening in different ways, the strengthening effect of the two roughly the same. Through the TEM analysis can determine the precipitation during aging precipitation phase is NiMn face centered tetragonal ordered phase, there are certain crystallographic orientation relationship and NiMn the matrix, specific orientation relationship: (002) matrix / / (001) NiMn, [100]matrix [100]NiMn., discontinuous precipitation growth rate and temperature. The JMAK equation and Aaronson-Liu model Discontinuous precipitation type description of Cu-20Ni-20Mn alloy growth kinetics, the discontinuous precipitation of grain boundary diffusion chemical activation energies were 72.7 + 7.2 and 94.1 + kJ/mol 16.8 kJ/mol, far less than Ni, the activation energy of Mn element diffusion in the matrix body required. This shows that the discontinuous precipitation nucleation precipitated out easily at the grain boundaries, which is why not temperature interval continuous precipitation reaction than continuous precipitation reaction. There is no competition between the continuous precipitation reaction and continuous precipitation reaction, precipitation of NiMn will inhibit discontinuous precipitation long, discontinuous precipitation may also engulfed the small size of the NiMn particles by TEM and. Small angle X ray scattering analysis can determine, when the size of NiMn phase is greater than 5nm, can effectively prevent the discontinuous precipitation of interface migration. Cold deformation will lead to dislocation density in the alloy The increase, which can not only promote the precipitation of NiMn phase, but also improve the strength of the alloy. The solid solution alloy after deformation is 95% after cold rolling, the yield strength reached 807Mpa. with precipitation of NiMn phase, the effect of dislocation strengthening gradually, precipitation strengthening will play a leading role. Reducing the grain size of the alloy can enhance the grain boundary the effect of strengthening, so as to improve the yield strength of alloy. Through the relationship between the size and the mechanical properties of the alloy of the grain, can determine the grain size and hardness of Cu-20Ni-20Mn alloy is consistent with the Hall-Petch line, the Hall-Petch equation can be expressed as Hv=82.6+0.28D-1/2. according to the potential application environment of Cu-20Ni-20Mn alloy, the impact properties of the alloy, friction properties and low temperature properties were studied study found that, when the temperature is 77K, the strength and elastic modulus of Cu-20Ni-20Mn alloy will be slightly increased. The intensity ratio and The elastic modulus ratio of the material strength is mainly controlled by the non thermal barrier. After cryogenic treatment, the lattice constants do not change, more stable performance. With prolonged aging time the impact toughness is gradually reduced. Under the condition of low temperature and cryogenic treatment, the impact of performance difference. With graphite as alloy friction pair, friction and Cu-20Ni-20Mn alloy materials under different aging conditions, the friction coefficient is constant, approximately 0.09.

【學位授予單位】：北京有色金屬研究總院
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG146.11

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本文編號：1658357