(1. 重慶大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400044；2. 重慶市科學(xué)技術(shù)研究院，重慶 401123)
摘 要: 研究750、800、850、900和950 ℃不同熔體過熱處理溫度對AZ31鎂合金凝固組織的影響規(guī)律。利用光學(xué)顯微組織定量分析經(jīng)不同溫度過熱處理所得AZ31鎂合金的二次枝晶間距等組織特征差異；開發(fā)一種采用能譜分析結(jié)果計算Mg、Al和Zn等主要元素在一個枝晶單元內(nèi)各個特征區(qū)域質(zhì)量分?jǐn)?shù)的方法，用以測評不同過熱溫度下凝固組織的成分均勻性。結(jié)果表明：當(dāng)過熱溫度從750 ℃增加到900 ℃時，成分偏析減少，鑄態(tài)組織中二次枝晶間距從13 μm減小到9 μm，多點隨機(jī)顯微硬度的平均值從36.5 HV增大到42.6 HV；AZ31鎂合金較理想的熔體過熱處理溫度為900 ℃。
關(guān)鍵字: AZ31鎂合金；過熱處理；凝固組織；枝晶間距；成分偏析
solidification microstructure of AZ31 magnesium alloy
（1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. Chongqing Academy of Science and Technology, Chongqing 401123, China）
Abstract:The effect of different overheating temperatures on the solidification microstructure of AZ31 magnesium alloy was investigated. The overheating temperatures of 750, 800, 850, 900 and 950 ℃ were applied. The secondary dendrite spacing of AZ31 magnesium alloy at different overheating temperatures was quantitatively investigated through the optical microstructures. A method was developed to analyze the mass fraction of Mg, Al and Zn elements in each region of a dendrite cell by scanning electron microscope with energy spectrum, which was used to assess the component homogenization of the solidification microstructures at different overheating temperatures. The results show that with the increase of overheating temperature from 750 to 900 ℃, the chemical composition segregation is reduced, the secondary dendrite spacing is decreased from 13 to 9 μm, and the average value of multi-point random microhardness is increased from 36.5 HV to 42.6 HV. The better melt overheating temperature of AZ31 magnesium alloy is 900 ℃.
Key words: AZ31 magnesium alloy; superheating treatment; solidification microstructure; dendrite spacing; composition segregation
