A7075/A7050高強度鋁合金異質銲接與銲後熱處理之微觀組織與機械性質之研究

Abstract

本研究對航空結構元件材料，A7075 與A7050 之鋁合金進行熱處理與銲接製程基礎研究。本實驗採用氣體鎢極電弧銲，並加入填料ER5183 與ER5356與ER5556 進行銲接。銲後再施予自然時效(T1)、固溶處理(T4)及固溶處理再人工時效(T6)。主要探討藉由不同方式的熱處理製程對材料機械性質與微結構之變化；不同銲料對熔融區機械性質與微結構之影響。並期望將此研究提供 於航空元件參考，以達到其輕量化及高強度等目的。 由金相實驗顯示，觀察其微觀組織，發現到經T4、T6 熱處理後會有大量析出物出現於熱影響區晶粒內部與晶界處，並有發現沿晶破裂之現象。銲件經熱處理後，由拉伸強度以及微硬度實驗中得知T6 熱處理後的UTS、YS 值均大幅提升，顯示固溶處理再人工時效可提升其熔融區內之機械性能。在破斷面微結構組織上T1狀態之破斷面為韌窩狀組織，屬延性破壞。試片經過T4處理，出現大量析出物於破斷表面，但仍屬延性破斷。經過T6處理，部分區域破斷面保持韌窩狀組織，但部分區域轉趨偏向為脆性破壞。

The article was investigated on the A7050 and A7075 dissimilar welding and it’s mechanical properties for post-weld heat treatment process. In this experiment, tungsten inert gas (TIG) welding process was utilized to make weldments with filler metals of ER5183 and ER5356 and ER5556. The effect of heat treatment of natural aging (T1), solution treatment(T4), and solution treatment plus artificial aging(T6) on the weldment were investigated. The tensile test, microhardness test, and optical microscope were used to study the mechanical properties and microstructures the effect of different trace elements on the material mechanical properties and microstructure is also determined. After T4 or T6 heat treatment, multiple precipitates were found in heat affected zone(HAZ) grain and grain boundaries. The microhardness, ultimate tensile strength, and yield strength of the heat treated weldment were greatly enhanced by the heat treatment. The fractured surface of T1 treatment shows dimple appearance indicating some ductility. In T6 treatment, some region maintain dimple surface, some region tend to brittleness cracking.