(1. 哈爾濱工業(yè)大學(xué)(威海) 山東省特種焊接技術(shù)重點實驗室，威海 264209；
2. 蘇州熱工研究院，蘇州 215004)
摘 要: 對56 mm厚Ti-6Al-4V合金進行窄間隙磁控電弧TIG焊接，通過金相顯微鏡對接頭各區(qū)組織進行對比分析。結(jié)果表明：在窄間隙的多層單道焊接中，接頭各區(qū)的組織、結(jié)晶形態(tài)及生長方向存在很大差異。焊縫區(qū)一次結(jié)晶組織為表層焊道上表面的柱狀粗大組織及熔合線附近、焊道內(nèi)部的等軸晶組織。熔合線處，電磁作用提高了平面狀結(jié)晶前沿及后來形成的等軸晶的穩(wěn)定性，最終隨著磁場強度的增加在熔合線附近逐漸由柱狀晶轉(zhuǎn)變?yōu)榈容S晶。焊縫中心處，磁控電弧作用使得生成的等軸晶穩(wěn)定性提高，隨著磁場強度的增加，等軸晶逐漸單方向伸長，在熱傳導(dǎo)方向上，即焊縫表層垂直方向生成粗大的柱狀晶。
關(guān)鍵字: Ti-6Al-4V合金；磁場；窄間隙焊接；焊縫組織
（1. Shandong Provincial Laboratory of Special Welding Technology, Harbin Institute of Technology at Weihai,
Weihai 264209, China;
2. Suzhou Nuclear Power Research Institute, Suzhou 215004, China）
Abstract:A narrow-gap controlling magnetic field TIG welding experiment was conducted directing at the 56 mm-thickness Ti-6Al-4V titanium alloy. Afterwards, an analysis was taken to compare each weld joint microstructure by means of metallographic microscope. The results show that, during the multilayer single channel of narrow gap welding, the joint microstructure, the crystal structure and the growth orientation significantly differ from each other. The first crystal structure in the weld zone is an equiaxed grain which shows a columnar coarse grain at the top layer of the weld surface and near the bond line and the internal weld. Since the electromagnetic effect improves the stability of flat crystal and the equiaxed grains appear afterwards, ultimately, there are equiaxed grains translated from coarse columnar grains in the front of bond line with the magnetic field strength increasing. Due to the effect of magnetic controlled arc on improving the stability of equiaxed grains, along with the magnetic field strength increasing, the equiaxed grains gradually extend in a single direction; in the direction of heat conduction, i.e., in the vertical direction of the weld surface, the coarse columnar grains generate.
Key words: Ti-6Al-4V alloy; magnetic field; narrow-gap welding; weld microstructure
