高强稀土镁合金挤压构件内部面积型缺陷分析

Analysis of internal area defect of high strength rare earth magnesium alloy extrusion part

对高强Mg-Gd-Y-Zn-Zr镁合金挤压成形构件进行超声波探伤检测时,发现在其距离底部100 mm处50 mm×60 mm范围内存在面积性缺陷。为了分析缺陷产生的原因,对缺陷部位进行解剖取样,利用低倍、金相显微镜、扫描电镜、显微硬度计等检测手段对缺陷部位进行宏观和微观等详细检测与分析。结果表明:该缺陷宏观上呈现为不规则的带状条纹,微观上表现为大面积Zr和Zn等硬颗相的聚集,这种大面积硬颗粒相的聚集,势必引起该硬度不均匀区域的变形不协调,导致其过早断裂失效,影响其承载能力。同时为了消除Zr和Zn颗粒聚集的缺陷,提出了工艺改进措施。

Internal area defect of the high strength Mg-Gd-Y-Zn-Zr magnesium alloy extrusion part was detected during ultrasonic testing,and it was located at 100 mm from the bottom,and within the scope of 50 mm×60 mm.In order to analyze the formation reasons of defects,the defect position was dissected for sampling.The detailed macro and micro testing analysis were carried out using macro-examination,metallographic microscope,scanning electron microscope and micro-hardness tester.The results showed the defect had irregular strip morphology on the macro level,and it showed the large area aggregation of hard particles of Zr and Zn on the micro level.The large area aggregation of hard particles was bound to cause deformation incompatibility in this hardness heterogeneous region,leading to early fracture and cracking failure,thus influencing the load bearing capability.In order to eliminate the defects caused by the aggregation of Zr and Zn particles,the process improvement measures were proposed.