Elementary processes which govern the formation of nano grained and ultra fine grained (N&UFG) zones during oscillating sliding high temperature wear (HTW)

HTW限制了许多技术上重要的金属系统的可利用的使用寿命，例如柴油发动机中的阀/阀座摩擦系统。当金属摩擦系统暴露于HTW时，摩擦层在磨损伙伴的表面区域中形成。这些层对于了解耐磨性的微观结构至关重要。目前的项目旨在研究摩擦层的一个特定的更深的区域，在HTW过程中，纳米晶体和超细晶粒结构（N&UFG）的发展。需要理解导致形成该N&UFG区的基本微观结构过程，以理解在高于K熔点的一半的温度下控制HTW的机制。在HTW暴露（不同程度）后，将使用聚焦离子束提取（FIB）从表面区域采集样本。然后，N&UFG区域将使用扫描透射电子显微镜（STEM）结合高角年暗场（HAADF）检测器进行分析，这是一种非常适合于研究集体现象的TEM方法，取决于足够大的微结构区域中的位错和平面缺陷。调查将使用两个经典的模型铝合金，Al 11 Zn和Al 5 Mg，这已被报道为不同的倾向，形成位错诱导的亚结构在蠕变过程中，在严重的塑性变形。它们将在300至500°C的温度范围内（在Ar气氛和空气下）作为盘材料暴露于磨损载荷。将使用工具钢（德国等级：100Cr 6）制成的耐磨销作为对应体。拟议项目的科学目标是有助于更好地了解控制HTW条件下金属材料中形成的摩擦层N&UFG区的形成和演变的基本过程。

HTW limits the exploitable service life of many technologically important metallic systems, like for example valve/valve seat tribo systems in Diesel engines. When a metallic tribo system is exposed to HTW, tribo layers form in the surface regions of the wear partners. These layers are of central importance for the microstructural understanding of wear resistance. The present projects aims at studying a specific deeper zone of the tribo layer, where a nano crystalline and ultrafine grained structure (N&UFG) develops during HTW. The elementary microstructural processes which lead to the formation of this N&UFG zone need to be understood to appreciate the mechanisms which govern HTW at temperatures above half of the melting point in K. After HTW exposure (of different degrees), specimens from the surface regions will be taken using focused ion beam extraction (FIB). Then the N&UFG regions will be analyzed using scanning transmission electron microscopy (STEM) in combination with a high angular annual dark field (HAADF) detector, a TEM method which is well suited to investigated collective phenomena depending on dislocations and planar defects in sufficiently large microstructural regions. The investigations will be performed using two classical model Al alloys, Al11Zn and Al5Mg, which have been reported to differ in their tendencies to form dislocation induced substructures during creep and during severe plastic deformation. They will be exposed to wear loading as disk materials in the temperature range between 300 and 500°C (under Ar atmosphere and air). A wear resistant pin made out of tool steel (German grade: 100Cr6) will be used as counter body. The scientific objective of the proposed project is to contribute to a better understanding of the elementary processes which govern the formation and evolution of the N&UFG zones of tribolayers which form in metallic materials under conditions of HTW.