高强镁合金薄板激光焊接接头热裂机制及控制技术研究

项目名称： 高强镁合金薄板激光焊接接头热裂机制及控制技术研究

项目编号： No.51274092

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 矿业工程

项目作者： 严红革

作者单位： 湖南大学

项目金额： 80万元

中文摘要： 针对高强变形镁合金板材焊接成形困难特别是焊接热裂严重的现状，申请人提出通过细化合金微观组织和调控析出相尺寸与分散性等以抑制液化裂纹形成和通过焊接熔池稀土微合金化缩小凝固温度区间和细化凝固组织以抑制结晶裂纹形成的思想。以焊接热裂倾向严重的高Zn含量Mg-Zn-Zr系和高Al含量Mg-Al-Zn系变形镁合金薄板为研究对象，系统研究工艺参数和母材微观组织特征（母材晶粒尺寸、第二相尺寸及分布特征等）对镁合金激光焊接接头半熔化区液化裂纹形成的影响规律，探明在优化的工艺条件下半熔化区液化裂纹的形成与母材微观组织特征之间的关系，明确焊接熔池凝固过程对半熔化区液化反应机制和液化裂纹形成的影响，考察焊接熔池稀土微合金化对焊缝凝固组织特征和结晶裂纹形成的影响，明确焊缝区结晶裂纹的形成机制，提出抑制焊接热裂的具体措施。藉此探索一条抑制高合金含量镁合金焊接热裂倾向的新途径，为高热裂倾向合金材料的焊接提供理论指导。

中文关键词： 高强镁合金；激光焊接；液化裂纹；结晶裂纹；焊接热裂

英文摘要： Aimed at the current difficulties in weld forming of high-strength wrought magnesium alloy sheets especially the severe weld hot cracking tendency, the applicants propose the thoughts that the prohibition of liquid cracking can be achieved by microstructure refinement and modification of the size and the distribution of the precipitates and the prevention of solidification cracking can be realized by the reduced solidification temperature range and the refined as-solidified microstructure associated with micro-alloying of the welding pot with the RE element. The high hot-crack susceptible wrought magnesium alloy sheets of the high Zn Mg-Zn-Zr series and the high Al Mg-Al-Zn series are selected for the present study. The influences of the welding techical parameters and the microstructure features of the alloy matrix such as grain size, size and distribution of precipitation on the formation of liquid cracking in the half-fused zone of the laser-welded joints will be studied, and thus the correlations between the formation mechanism of liquid cracking and the microstructure features under the optimal welding parameters will be clarified. The effects of the solidification of the weld pot on the liquidification recation and the formation in the half-fused zone under will be explored. The effects of the micro-allo

英文关键词： High Strength Magnesium Alloy；Laser Welding；Liquaton Cracking；Solidification Cracking；Hot Cracking