高强高弹Cu-20Ni-20Mn合金微观组织结构演变规律及其对性能的影响

发布时间：2018-03-24 12:46

本文选题：Cu-Ni-Mn系合金　切入点：不连续析出反应　出处：《北京有色金属研究总院》2016年博士论文

【摘要】：Cu-20Ni-20Mn合金是一种典型的高强高弹无铍铜合金,具有与铍青铜相当弹性模量和强度,其高温稳定性优于铍青铜,是一种潜在的铍青铜替代材料。迄今,已有研究通过Cu-Ni-Mn系合金热力学相图和组织观察,初步阐明了Cu-20Ni-20Mn合金的时效析出行为。为更系统的研究时效过程中Cu-20Ni-20Mn合金的组织演变规律及其强化机制,本文利用金相与电子显微技术,X射线衍射等分析方法对Cu-20Ni-20Mn合金组织结构进行了观察;采用拉伸、冲击和摩擦等性能测试手段测量合金的力学性能。通过分析微观组织结构与力学性能之间的内在关系,构建合金微观组织结构-强化机制-力学性能间的映射关系,并探索Cu-20Ni-20Mn合金在不同服役条件下微结构特征对综合力学性能的调控机制。Cu-20Ni-20Mn合金中会发生三种固态相变反应,即不连续析出反应,连续析出反应,以及沉淀相的回溶反应。使用金相显微镜(OM)、扫描电子显微镜(SEM),观察各温度区间Cu-20Ni-20Mn合金的微观组织演变,结合DSC曲线分析合金升温过程中的热力学变化,以确定合金的固态相变反应温度。合金不连续析出反应发生的温度范围为200℃-475℃;连续析出反应发生的温度范围为350℃-475℃;合金固溶线温度在500℃至525℃之间。在不连续析出反应过程中,在晶界处形核析出由片层状NiMn相与贫溶质原子基体组成的不连续析出组织,由于合金中较高强度不连续析出组织,合金强度能明显提高;发生连续析出反应时,NiMn相颗粒在基体中弥散析出,由于弥散强化的作用能有效提高合金强度。在350℃(不连续析出反应为主导)和450℃(连续析出反应为主导)时效的峰值硬度分别为451Hv和436Hv,这说明两种时效析出反应能够通过不同的强化方式提高合金强度,二者的强化效果大致相同。通过TEM分析可以确定时效过程中析出的沉淀相是有序的面心四方结构NiMn相,NiMn相与基体存在一定的晶体学取向关系,具体的取向关系为:(002)matrix∥(001)NiMn,[100]matrix∥[100]NiMn。不连续析出组织的长大速率与温度有关。通过JMAK方程和Aaronson-Liu模型描述Cu-20Ni-20Mn合金的不连续析出长大动力学过程,得出不连续析出组织的晶界化学扩散激活能分别为72.7±7.2 kJ/mol和94.1±16.8 kJ/mol,远小于Ni、Mn元素在基体中发生体扩散所需的激活能。这说明不连续析出组织易于在晶界出形核析出,这也是不连续析出反应的温度区间要大于连续析出反应的原因。不连续析出反应与连续析出反应存在竞争关系,弥散析出的NiMn相会抑制不连续析出组织的长大,不连续析出组织也可能会吞噬尺寸较小的NiMn相粒子。通过TEM和小角X射线散射分析可以确定,当NiMn相尺寸大于5nm,能够有效阻碍不连续析出组织界面前沿的迁移。冷变形将导致合金中的位错密度增加,这不仅能促进NiMn相的沉淀析出,还能提高合金强度。固溶态合金经过变形量为95%的冷轧后,其屈服强度达到807Mpa。然而随着NiMn相的弥散析出,位错强化效果逐渐减弱,沉淀强化将起到主导作用。合金晶粒尺寸减小可以增强晶界强化的效果,从而提高合金屈服强度。通过对比晶粒尺寸与合金力学性能的关系,可以确定Cu-20Ni-20Mn合金晶粒直径与硬度符合Hall-Petch关系相符,其Hall-Petch方程可以表示为Hv=82.6+0.28D-1/2。根据Cu-20Ni-20Mn合金的潜在应用环境,对合金的冲击性能、摩擦性能以及低温性能进行了研究。研究发现,当温度为77K,Cu-20Ni-20Mn合金的强度和弹性模量会略微升高。通过强度比与弹性模量比可知材料强度主要是受到非热障碍控制的。深冷处理前后,材料晶格常数没有变化,性能较为稳定。合金的冲击吸收功所随时效时间的延长逐渐的减小。低温条件下和深冷处理后,合金的冲击性能差别不大。以石墨作为摩擦副,与不同时效状态下的Cu-20Ni-20Mn合金材料进行摩擦,其摩擦系数是恒定的,约为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.

【学位授予单位】：北京有色金属研究总院
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG146.11

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