鋁合金6061與7075之異種焊接性研究

Abstract

鋁合金6061和7075有高強度重量比與良好的抗腐蝕性，但銲接性 差，特別是鋁合金7075。主要的問題有雙形、氣孔、熱裂和熱影響區 (HAZ)強度降低。 本研究是探討析出硬化型鋁合金6061和7075，施以惰氣金屬極電 弧銲(GAMW)的銲接，使用ER4043和ER5356為填料。實驗項目包括：脈 衝銲接電流、銲後熱處理、微硬度試驗、拉伸試驗、彎曲試驗、光學 顯微鏡觀察、SER和EPMA等。研究機械性質和微觀組織之間的關係。 實驗結果顯示：使用適當的預熱能使鋁合金7075之銲件，降低熱 裂的生成。適當的銲後熱處理，能有效提昇銲道和熱影響區的強度。 析出物在晶界聚集與晶粒的偏析，將使銲件7075鋁合金產生熱裂。氣 孔的含量，脈衝電流銲接一般比連續電流銲接來的少。增加ZN的溶入 量，能增強銲件的最大抗拉強度。

Aluminum 6061 and 7075 have high strength of weight ratio and good corrosion resistance but they are poor in weldability, 7075 especially. The major problems are distortion, porosity, hot cracking and HAZ strength reduction. This research was to explore the weldability of 6061 and 7075 precipitated hardening aluminum alloys under Gas Metal Arc (GMA) welding process, and filler metals ER4043 and ER5356 were used. A series of experiments including pulsed welding current, post weld heat treatment, micro hardness testing, tensile testing, bending test, optical microscope, SEM and EPMA were used to investigate the relationship between mechanical properties and microstructure. The experimental results showed that hot cracking canbe reduced in 7075 aluminum alloy welds made with suitable preheat. The proper post weld heat treatment can effectively increae the strength in fusion zone and HAZ. Precipitation in grain boundary and grain interior can cause hot cracking in 7075 aluminum alloy weld. The porosity content of the pulsed-current weld is in general found to be comparatively lower than that of the continuous current weld. The increase in zinc pickup in fusion zone can enhances the ultimate tensile strnegth of the weldment.