服役高铁制动盘微观组织演变和力学性能表征  

Characterization and evolution of microstructure and mechanical properties of serviced high-speed rail brake discs

作　　者：谢晓东 李志强[1] 刘志成 李志龙 杨智勇[1] 李卫京[1] 韩建民[1] XIE Xiaodong;LI Zhiqiang;LIU Zhicheng;LI Zhilong;YANG Zhiyong;LI Weijing;HAN Jianmin(School of Mechanical,Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China;CRRC Qingdao Sifang Co.Ltd.,Qingdao 266111,China)

机构地区：[1]北京交通大学机械与电子控制工程学院,北京100044 [2]中车青岛四方机车车辆股份有限公司,山东青岛266111

出　　处：《中南大学学报（自然科学版）》2022年第10期3869-3878,共10页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(52002018)。

摘　　要：以高速列车铸钢制动盘为研究对象,借助SEM和TEM手段表征服役后铸钢制动盘微观组织演变,通过拉伸试验测试服役制动盘的力学性能,采用热循环和DIC拉伸试验研究制动盘材料力学性能退化机理。研究结果表明:在摩擦制动导致的大温度梯度、不同的冷却速度下,制动盘表层局部区域发生了“自淬火”并形成细小的马氏体晶粒;摩擦剪切作用产生的塑性变形进一步细化晶粒并形成粒径小于50 nm的纳米晶,局部晶粒细化和相变使制动盘表层至心部以及沿表层方向上的组织呈现出晶粒粒径非均匀分布的特征。服役制动盘表层材料的屈服强度、抗拉强度以及断后伸长率相比新材料分别衰退了20.1%,21.2%和43.3%。制动盘表层晶粒粒径非均匀分布使断口呈现出韧性与脆性的混合形貌以及裂纹的快速扩展特征。晶粒粒径非均匀分布在导致硬度非均匀分布的同时,还会使材料在承载时容易出现应力应变局域化进而导致材料承载能力下降。The cast steel brake disc of high-speed train was taken as the research object,the microstructure evolution of the cast steel brake disc after service was characterized by SEM and TEM,the mechanical properties of the service brake disc were tested by tensile test,and the mechanism of mechanical properties degradation of brake disc material was studied by thermal cycling and DIC tensile test.The results show that the"self-quenching"occurs in the local area of the brake disc surface layer at the large temperature gradient and different cooling rates caused by braking.The plastic deformation caused by frictional shear further refines the grains and forms nanocrystals with the size below 50 nm.The local phase transition and grain refinement make the sectional structure of the serviced brake disc show a characteristic of non-uniform grain size distribution.The serviced brake disc surface layer sample's yield strength,tensile strength and elongation are decreased by 20.1%,21.2%and 43.3%respectively.The non-uniform distribution of grain size on the surface of the brake disc makes the fracture surface present a mixed morphology of toughness and brittleness and the characteristics of rapid crack propagation.The non-uniform distribution of crystal grain sizes leads to non-uniform distribution of hardness,which results in stress and strain localization when it is loaded.This leads to a decrease in the material's load bearing capacity and degradation of mechanical properties.

关 键 词：制动盘 晶粒细化 晶粒粒径非均匀分布 应力应变局域化 力学性能衰退 

分 类 号：U271.91[机械工程—车辆工程]