表面深滚处理对钛、镍表面完整性的影响及其热稳定性

发布时间：2018-02-12 10:07

本文关键词： 深滚微观组织表面完整性超细晶热稳定性　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着现代工业技术的不断发展,对零部件材料性能的诉求日益提高。由于零部件的失效一般发生在材料表面,故而表面强化技术成为一种有效的延寿方法。其中表面机械强化可以通过细化晶粒在保证韧性的基础上大幅度提高其强度,从而延长零部件使用寿命。但在高温环境下强化组织往往处于不稳定状态,因此在高温环境下组织的演变及残余应力分布变化需要进行进一步分析。本文通过一种新型表面自纳米化方法一一表面深滚处理,在纯钛(TA2)与纯镍(N4)表面制备出晶粒尺寸小于500nm的超细晶梯度结构,并对材料表面微观组织结构、残余应力分布及力学性能进行了研究,分析其表面完整性变化及热稳定性。研究结果表明：(1)经过表面深滚处理,材料表层及次表层发生剧烈塑性变形,位错大量产生,晶粒明显细化,出现大量超细晶乃至纳米晶组织。(2)由于晶体结构的区别,纯钛与纯镍细化机制有所不同,纯钛主要依靠孪晶组织对原始晶粒进行分割形成小角度晶界,而纯镍中位错组织的演变占主导作用。小角度晶界向大角度晶界演变主要依靠连续动态再结晶。(3)滚压后组织表面形成具有一定厚度的残余压应力场,与原始材料相比处理后表面组织硬度提高,通过合理选择滚压参数,其细化层厚度、硬度、表面粗糙度及残余应力分布均得到不同程度改善。(4)在高温环境下深滚处理产生的残余应力会不断释放,晶粒尺寸也发生改变。
[Abstract]:With the continuous development of modern industrial technology, the demand for the material properties of parts is increasing. Because the failure of parts usually occurs on the surface of materials, Therefore, surface strengthening technology has become an effective method of life extension, in which surface mechanical strengthening can greatly improve the strength of grain on the basis of ensuring toughness. Thus prolonging the service life of the parts. However, the strengthening structure is often in an unstable state under the high temperature environment. Therefore, the evolution of microstructure and the change of residual stress distribution in high temperature environment need to be further analyzed. Ultrafine gradients with grain size less than 500nm were prepared on the surface of pure titanium (TA2) and pure nickel (N4). The microstructure, residual stress distribution and mechanical properties of the surface were studied. The analysis of surface integrity and thermal stability shows that after deep rolling treatment, the surface layer and subsurface layer of the material undergo severe plastic deformation, a large number of dislocations occur, and the grain size is obviously refined. Due to the difference of crystal structure, the refining mechanism of pure titanium and pure nickel is different. Pure titanium mainly depends on twin structure to split the original grain to form small angle grain boundary. The evolution of dislocation structure in pure nickel mainly depends on the continuous dynamic recrystallization. Compared with the original material, the hardness of the surface structure is improved. The thickness and hardness of the fine layer can be obtained by reasonably selecting the rolling parameters. The surface roughness and residual stress distribution are improved to some extent. 4) the residual stress produced by deep rolling treatment under high temperature will be released continuously and the grain size will be changed.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG306

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