火箭发动机内衬CuAgZr合金时效析出行为及力学性能

发布时间：2018-03-11 06:39

  本文选题：Cu　切入点：Ag　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：铜和铜合金经过热处理后具有较高的强度、电导率及耐高温低周期疲劳等特性,在航空航天领域具有广泛应用。随着航天事业的发展,火箭发动机内衬材料所需更高的高温、高压、耐高温低周期疲劳损伤等特性,现役的Cu Zr合金已不能满足后续航天事业的要求,研发新的火箭发动机内衬材料具有十分重要的意义。相比于Cu Zr合金,Cu Ag Zr合金具有更好的高温力学性能,在航空航天领域是一种极具应用价值的材料,Cu Ag Zr合金的热处理工艺与合金的组织结构及力学性能关系密切。本文通过XRD、DTA、光学显微镜、扫描电镜、透射电镜、室温拉伸试验、硬度测试等手段,系统的研究Cu Ag Zr合金不同热处理工艺制度、时效析出行为及力学性能。研究发现,热挤压态Cu Ag Zr合金有α-Cu基体和β-Ag与m相形成的共晶第二相,第二相呈带状沿着晶界不连续分布,并具有一定的方向性。随着固溶温度升高、保温时间延长,第二相由带状变为网状,球状,溶入基体中。同时,合金晶粒尺寸逐渐长大。Cu Ag Zr合金最佳固溶温度为940℃,固溶时间为10h。当固溶温度为960℃时,合金过烧。透射电镜观察发现,纳米Ag析出相形核长大变化规律如下:时效初期,球状纳米Ag析出相优先于位错上非均匀形核;随着时效时间的延长或时效温度的升高,球状纳米Ag析出相数量逐渐增多并长大;当球状纳米Ag析出相长大到一定尺寸,球状纳米Ag析出相在{100}面沿着011或011?延长成为杆状;当长度到一定程度,在过饱和的Cu基体无位错区中,新的纳米Ag析出相与拉长的纳米Ag析出相形核,并沿着相同的011或011?方向继续生长。时效时间的继续延长或时效温度的继续升高,纳米Ag析出相进入粗化阶段。TEM观察表明,时效过程存在不同时效析出相。在相同保温时间下脱溶序列为:球状纳米Ag析出相→杆状纳米Ag析出相→盘状纳米Cu Zr析出相→粒状富Zr析出相。在相同时效温度下脱溶序列为:球状纳米Ag析出相→杆状纳米Ag析出相→盘状富Zr析出相。硬度测试及室温拉伸试验研究表明,Cu Ag Zr合金强度随着固溶温度的升高,保温时间的延长而逐渐上升,当温度超过过烧温度,合金强度塑性急剧下降,不同固溶工艺下,合金都具有较高的延伸率。Cu Ag Zr合金在时效过程中,350℃时效,随着时效时间的延长,屈服强度、抗拉强度和硬度均呈现单调上升趋势;当温度超过400℃,随着时效时间的延长,合金屈服强度、抗拉强度和硬度先升高后降低,延伸率单调下降。在相同时效时间下,强度和硬度都随着时效温度的升高呈现先升高后降低趋势。随着时效温度的升高,时效峰所需时间迅速缩短。当时效温度超过700℃,合金硬度降到未时效以下。
[Abstract]:Copper and copper alloys are widely used in aerospace field because of their high strength, electrical conductivity and low cycle fatigue resistance after heat treatment. With the development of aerospace industry, the lining materials of rocket engine need higher temperature. Due to the characteristics of high pressure, high temperature and low cycle fatigue damage, the current Cu-Zr alloy can no longer meet the requirements of the subsequent aerospace industry. It is of great significance to develop new liner materials for rocket motor. Compared with Cu Zr alloy, Cu Ag Zr alloy has better mechanical properties at high temperature. The heat treatment process of CuAg-Zr alloy, which is a valuable material in the field of aerospace, is closely related to the microstructure and mechanical properties of the alloy. In this paper, the X-ray DTA, optical microscope, scanning electron microscope, transmission electron microscope, room temperature tensile test were used. By means of hardness measurement, the precipitation behavior and mechanical properties of Cu-Ag-Zr alloy under different heat treatment conditions were systematically studied. It was found that there were 伪 -Cu matrix and eutectic second phase formed by 尾 -Ag and m phase in hot extruded Cu-Ag Zr alloy. The second phase is distributed discontinuous along the grain boundary and has a certain directivity. With the increase of the solution temperature and the prolongation of the holding time, the second phase changes from banded to reticulate, globular and dissolved into the matrix, at the same time, The optimum solution temperature is 940 鈩，

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