某车型副车架材料的断裂失效分析

Fracture Failure Analysis of a Vehicle's Subframe Material

用扫描电镜对断裂失效的某车副车架样品进行断口形貌分析,对个别区域进行能谱分析,对球化等级与硬度进行检验。分析结果表明,副车架样品的球墨等级为2~3级,硬度为142 HBW,组织为球墨+铁素体。副车架外观检测表明,裂纹长约55mm,裂尖扩展方式为穿晶断裂;外沿中部的裂纹处有损伤。副车架样品的断口观察表明,断口表面覆盖红棕色锈层。断口锈层清洗后的扫描电镜和能谱观察发现,在外沿中部的损伤处有凹坑,在凹坑底部和侧部还有二次裂纹;裂纹扩展区由石墨和带后韧窝及撕裂痕迹的铁素体组成。基于检测结果分析可知,试块的开裂是起始于外沿中部的损伤凹坑处,然后在力和腐蚀环境作用下发生扩展;而裂纹的起源与外力冲击下的损伤以及该处的腐蚀有关。

The fracture morphology of a vehicle＇s subframe sample is analyzed by scanning electron microscopy （SEM）, and the energy spectrum analysis is carried out to examine the spheroidization degree and hardness of the individual region. The analysis results show that the ductile grade sub frame sample is 2 3 grade, hardness is HB142, and the microstructure is spheroidal graphite and ferrite. The subframe appearance test shows that the crack length is about 55 mm, the crack tip expansion is transgranular fracture, and the damage cracks along the central edge. The fracture observation of subframe sample shows that the fracture surface is covered with reddish brown rust layer. After cleaning the fracture rust layer, by the scanning electron microscope and energy spectral observation, there are pits in the injury is in the middle and two cracks at the bottom of the pit and the side. The crack growth area is composed of graphite, the rear toughened fossa and tearing ferrite. The detection and analysis based on the results of test block cracks pits originated in the outer middle, then in force and corrosive expansion; and crack origin and under the impact of external forces and the relevant corrosion damage. Based on the analysis of test results, test block cracks pits originate in the outer middle, then expand in force and corrosive envi ronment. The crack origin is related with the damage of external forces and the corrosion.