銲後熱處理對Ti-6Al-4V鈦合金薄板銲件之機械性質影響研究

Abstract

本研究主要針對鈦合金經過雷射銲接後，實施後續的熱處理。探討鈦合金銲件經過熱處理之後，其機械性質的改變。實驗用的材料為Ti-6Al-4V鈦合金，材料厚度為1.2mm，銲接方式則採用300W之Nd : YAG雷射，採取不添加任何填料的對接方式。銲接過後，再實施不同熱處理實驗。熱處理分別為退火處理(705℃/恆溫2小時/爐冷)及固溶(955℃/恆溫15分鐘/水淬)加時效處理(530℃/恆溫4小時/空冷)兩種，來進行熱處理實驗。 本實驗結果獲得幾項結論： 1、Ti-6Al-4V鈦合金銲件實施熱處理，則銲件之抗拉強度及降伏強度會增 加。 2、針對延伸率而言，經退火處理後的延伸率與原銲件相差不大，差了 0.1%；但是經過固溶加時效處理的延伸率則會大幅下降，從10.7%下降至1.3%，差了9.4%。 3、以破壞方式分析，Ti-6Al-4V銲件及銲件經退火處理的破壞為延性破壞；銲件經固溶加時效處理的破壞方式，偏向脆性破壞。 4、針對硬度分佈討論，Ti-6Al-4V鈦合金銲件在銲道區硬度值最高；在熱影響區(HAZ)硬度值最低。銲件經過退火處理及固溶加時效處理後，整體硬度會提升。

The research mainly aims for the mechanical properties changes of titanium alloy which was welded by laser after heat treatment. Ti-6Al-4V, possesses thickness of 1.2mm, was selected for welding without the use of filler material. After welded by 300W Nd:YAG laser, Ti-6Al-4V proceeds respectively in two different kind of heat treatment：ANN(705℃/2hrs/FC)and S.T.(955℃/15min/WQ)+A.A.(530℃/4hr/AC). We know several conclusions from the experiment results: 1、After heat treatment of Ti-6Al-4V titanium alloy welded, the ultimate tensile strength and yield strength are increasing. 2、After ANN, the elongation of Ti-6Al-4V welded is 10.7%, it’s not different to the weldment of no heat treatment. But after S.T.+A.A., the elongation of weldment is decreased from 10.7% to 1.3%. 3、The Ti-6Al-4V welded and the Ti-6Al-4V welded after ANN are present the feature of ductility fracture. But the welded after S.T.+A.A. is tend to brittle fracture. 4、By vickes hardness test, the hardness of FZ is highest and HAZ is lowest, after S.T.+A.A. and ANN, the hardness will promoted.