FGH96合金原始粉末颗粒边界形成机理及演化规律研究

发布时间：2018-03-18 00:14

本文选题：原始粉末颗粒边界　切入点：热等静压成形　出处：《中北大学》2017年硕士论文　论文类型：学位论文

【摘要】：FGH96合金是我国研制的第二代粉末高温合金,该合金具有优异的裂纹扩展抗力、蠕变强度以及损伤容限等性能,是制造大推重比航空发动机涡轮盘等热端部件的首选材料。使用氩气雾化法(AA)或旋转电极法(PREP)制备的FGH96合金粉末,经热等静压成形后组织中一般会存在原始粉末颗粒边界(PPB),PPB是粉末高温合金的三大缺陷之一,对合金的组织和性能非常不利。本文围绕FGH96合金中的PPB,开展了以下工作:(1)以粉末粒度和粉末氧含量为热等静压成形(HIP)变量,研究了PPB的形成机理及影响因素。研究表明,PPB是由粉末表面吸附的C、O以及表面富集的Ti、Cr、Al的氧化物在HIP时与内部迁移的Ti、Nb等元素一起形成的边界聚集物,主要由大尺寸γ′相和少量的氧化物、碳化物或碳氧化物组成;热等静压成形时,PPB沿粉末颗粒边界析出,PPB的析出程度受粉末粒度影响较小,与粉末氧含量成正比。(2)以HIP态的FGH96合金为研究对象,通过热变形(HIF)和热处理(HT)试验研究了PPB的演变规律。研究表明,PPB处的大尺寸γ′相以及组织内的二、三次γ′相在热变形和热处理过程中逐渐融入基体,转而析出大量小尺寸γ′相和一些碳化物、氧化物或碳氧化物。(3)通过原位拉伸和原位疲劳试验,研究了FGH96合金的损伤力学行为。研究表明,原位拉伸试验过程中,材料处于过载状态,断裂特征为沿PPB发生的脆性断裂;原位疲劳试验过程中,疲劳裂纹的萌生、扩展由滑移、孪晶及晶界主导,疲劳断口瞬断区有沿PPB开裂的断裂特征,材料的疲劳寿命与PPB相对等级成反比。
[Abstract]:FGH96 alloy is the second generation powder superalloy developed in China. It has excellent crack growth resistance, creep strength and damage tolerance. FGH96 alloy powder prepared by argon atomization method or rotating electrode method is the preferred material for the manufacture of hot end parts such as turbine disk of aeroengine with large push-weight ratio. After hot isostatic pressing, there are usually three defects in the microstructure of the powder superalloy, which are the original powder particle boundary and the PPB. In this paper, the following work has been carried out around the FGH96 alloy: the powder size and the oxygen content of the powder are taken as the variables of hot isostatic pressing forming (hip). The formation mechanism and influencing factors of PPB were studied. The results show that the PPB is a boundary aggregate formed by the Con O adsorbed on the powder surface and the oxides enriched on the surface of TiOCr-Al during HIP, along with the elements such as TiONb, which are transported internally, and so on. It is mainly composed of large size 纬 'phase and a small amount of oxides, carbides or carbon oxides, and the precipitation degree of PPB along the boundary of powder particles is less affected by particle size during hot isostatic pressing. The evolution of HIP alloy was studied by means of hot deformation and heat treatment. The results showed that the large size 纬 'phase and the two phases in the structure of PPB were studied. The cubic 纬 'phase gradually melts into the matrix during hot deformation and heat treatment, and in turn precipitates a large number of small 纬' phases and some carbides, oxides or carbon oxides. The damage mechanical behavior of FGH96 alloy has been studied. The results show that during in-situ tensile test, the material is in a state of overload and the fracture is characterized by brittle fracture along PPB, and during in situ fatigue test, the fatigue crack initiation and propagation are caused by slip. The twinning and grain boundary are dominant, and the fracture characteristics of the transient fracture zone of fatigue fracture are along PPB. The fatigue life of the material is inversely proportional to the relative grade of PPB.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG132.3;TF123.71

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