真空脱氢对Sr变质ZL114A焊缝组织性能影响研究

Effect of Vacuum Dehydrogenation on Welding Mechanical Properties and Microstructure of ZL114A alloy Modified by Strontium

摘要:

通过选用不同厚度与状态的焊接副与焊丝,完成了Al-Sr中间合金硅相变质ZL114A合金的氩弧焊堆焊处理,利用电感耦合法(ICP)测定了材料的化学成分,分别采用电子测氢仪、万能试验机、金相显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)与透射电镜(TEM)全面分析了真空脱氢对Sr变质ZL114A焊缝区域微观组织与力学性能的影响。结果表明：焊接副与焊丝经真空脱氢处理,氢含量由0.64×10_-6降至0.26×10_-6,24mm与12mm壁厚焊缝区域气泡数量各降低71.4%与60%,气泡直径由2.3mm与1.8mm降至1.4mm与1.2mm,面密度各降低77.7%与81.8%。沿晶界均匀分布的初生与共晶Si相经Sr元素变质处理,形貌由针状转变为球状,颗粒尺寸由106μm降至12μm,12mm壁厚焊缝区域平均抗拉强度、屈服强度、延伸率与断面收缩率分别为364MPa、332MPa、9.8%与14.2%。焊缝区域T6态微观组织主要由初生α-Al、初生与共晶Si相及Mg₂Si时效相组成,断口表面晶界处硬脆Si相颗粒直径约为4μm,Mg₂Si时效相呈长棒状,长宽比约为15.2,经真空脱氢处理,断口韧窝形貌由椭圆状过渡为球状,断裂机制由沿晶断裂演变为韧窝断裂。

Abstract:

The TIG welding process of ZL114A aluminum alloy that modified by Al-Sr master alloy was obtained by selecting welding vice and wire with different states and thicknesses. The chemical composition of the material was determined by inductively coupled method, and the effect of vacuum dehydrogenation on microstructure and mechanical properties nearby welding region were analyzed by Electronic hydrogen measuring instrument, OM, SEM, EDS, TEM and Universal testing machine. The results show that the hydrogen content decreases from 0.64×10_-6 to 0.26×10_-6, accompanying with the number of bubbles within 24mm and 12mm thickness reduce 71.4% and 60% individually, the diameter decrease from 2.3mm and 1.8mm to 1.4mm and 1.2mm, together with a reduced surface density by 77.7% and 81.8% after the vacuum dehydrogenation process. The morphology of silicon phase that distribute nearby grain boundaries transforms from needle-like to spherical, the particle size reduces from 106μm to 12μm, the average tensile strength, yield strength, elongation and reduction of area of 12mm thickness are 364MPa, 332MPa, 9.8% and 14.2%. The microstructure under T6 state mainly contains primary α-Al, primary and eutectic Si phase and Mg₂Si aging phase, the diameter of brittle Si particle is 4μm, Mg₂Si aging phase shows a rod-like morphology and the aspect ratio is 15.2, the shape of dimple changes from elliptical to spherical and the fracture mechanism evolves from intergranular frcture to dimple rupture after vacuum dehydrogenation.