【作者】 王大鹏；

【导师】 来忠红；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 硕士

【摘要】 本文通过真空熔炼制备了3J33马氏体时效钢,在研究3J33马氏体时效钢时效硬化行为的基础上,借助光学显微镜、扫描电镜、透射电镜以及X衍射等分析手段探索了3J33马氏体时效钢时效过程和循环相变晶粒细化过程中的组织演变规律;利用万能电子拉伸试验机、洛氏硬度仪和显微硬度仪对材料力学性能进行测试;对原有的循环相变晶粒细化工艺进行了优化,并对3J33马氏体时效钢表面机械研磨晶粒细化工艺进行了初步探索,为最终实现3J33马氏体时效钢组织纳米化并具有优良的综合性能提供依据。研究结果表明,3J33马氏体时效钢不同温度时效过程中表现出相似的时效硬化行为,时效不存在孕育期,普遍存在两个时效硬化峰;时效初期硬度增加极快,迅速达到第一个时效硬化峰,此时可观察到基体衍射斑点拉长,说明3J33马氏体时效钢时效初期发生了调幅分解;时效后期随着时效时间的延长,硬度的上升趋势缓慢,并逐渐形成第二个时效硬化峰,此时对应着析出相不断地析出并长大过程。3J33马氏体时效钢α′?γ等温循环相变细化晶粒工艺研究结果表明,3J33马氏体时效钢的再结晶温度为900℃;3J33马氏体时效钢900°C,15min ,5次循环细化工艺处理可获得良好的晶粒细化效果,晶粒最终尺寸可达8μm左右;循环细化并没有改变时效析出行为的本质,但可加速时效的动力学过程;材料经循环细化时效后,抗拉强度σb可达2048MPa,延伸率δ可达9.82%,表现出良好的综合力学性能。表面机械研磨(SMAT)的研究表明,经过60min SMAT处理后,试样表面产生厚度约为15μm的变形层,塑性变形程度随距离表面深度的增加而逐渐减弱;试样表面可形成500nm左右的亚晶粒,在亚晶粒内部和其边界处有高密度的位错、层错存在;试样最表面的显微硬度可以提高100HV,从试样表面到基体,显微硬度逐渐减小,直至到与基体持平。更多还原

【Abstract】 3J33 maraging steel has been prepared by vacuum melting and the evolution of microstructures during aging and cycle phase transformation refining grain (CPTRG) are investigated by Optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The mechanical properties of 3J33 maraging steel are tested by tensile testing machine, rockwell hardness tester and micro-hardness tester. In order to achieve refining grain and good mechanical properties of 3J33 maraging steel, the process parameter of CPTRG was optimized and surface mechanical attrition treatment (SMAT) was explored.The results show that 3J33 maraging steel presents the similar aging behaviors at different temperature. Two aging peaks and no incubation period are found during aging process. At the initial aging stage, the hardness increases rapidly and reaches the first aging peak. The elongated diffraction patterns reveal that spinodal decomposition may be occur at the initial aging stage. At final aging stage, the hardness increase slowly and the second aging peak is formed with the increase of time.The results of 3J33 maraging steelα’-γCPTRG show that the recrystallization temperature was 900°C. The optimal grain refinement technology is 900°C, 15min four times’cyclic solution treatment and the grain size was decreased to about 8μm. CPTRG did not change the aging mechanism but increase the speed of aging. The good mechanical properties of 3J33 maraging steel, such asσb 2048MPa andδ9.82%, are obtained by the CPTRG and following aging treatment.The results of SMAT for 60min show that deformation layer of 15μm in depth were formed on the surface of sample. The plastic deformation becomes not more obvious with the increase of depth. The grain size of the surface is about 500nm, and the high density dislocations and stacking faults were found in the subgrain or on the boundary of the subgrain. The microhardness of surface increases 100HV, and the microhardness decrease gradually from surface to matrix until it becomes the same as matrix’s.更多还原