خواص ناحيه‌ي جوش در جوشكاري اصطكاكي اغتشاشي زير آب و جوشكاري اصطكاكي اغتشاشي قرار گرفته تحت خنك كار آب

Properties of Welding Area during Underwater Friction Stir Welding & Friction Stir Welding with Cooling Effect of Water

جوشكاري اصطكاكي اغتشاشي، نوعي روش نوين جوش حالت جامد است كه نخستين بار براي آلياژهاي آلومينيومي كه به رو شهاي سنتي جوشكاري (جوشكاري ذوبي) جوشپذير نبودند ابداع شد. جوشكاري اصطكاكي اغتشاشي زير آب و فرايند خنك كاري به وسيله‌ي آب در حين جوشكاري اصطكاكي اغتشاشي، راهبردي موثر براي بهبود خواص ناحيه‌ي جوش است. در اين مقاله، به مرور و بررسي اثر خنك‌كاري به وسيله‌ي آب در حين جوشكاري اصطكاكي اغتشاشي و نيز اثر جوشكاري اصطكاكي اغتشاشي زير آب بر توزيع دما، ريزساختار ماده، توزيع سختي، خواص مكانيكي، موقعيت ناحيه‌ي شكست و سطح شكست در ناحيه‌ي جوش هنگام جوشكاري صفحات فلزي نازك و نيز تاثير پارامترهاي جوشكاري (سرعت پيشروي و سرعت چرخشي) پرداخته شده است. عمليات خنك‌كاري به‌ وسيله‌ي آب و نيز جوشكاري اصطكاكي اغتشاشي زير آب، موجب كاهش بيشين هي دما و همچنين كاهش مدت زمان قرارگيري در دماهاي زياد و ايجاد ساختار مطلوب دانه‌ها، تراكم زياد نابه‌جايي‌ها (گاهي)، افزايش سختي و در نهايت افزايش استحكام كششي خواهد شد. شايان ذكر است كه استفاده از آب داغ به‌عنوان ماده‌ي خنك‌كننده، بيشترين و مطلو ب‌ترين خواص مكانيكي را در اتصال جوش به دست مي‌دهد.

Friction stir welding (FSW) is a relatively new solid-state joining process. It was first used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. Underwater friction stir welding as well as cooling with water during friction stir welding are effective ways to improve joint properties. In this review paper, we review temperature distribution, microstructure, hardness profile, mechanical properties, fracture location, and fracture surface of the welding area during underwater friction stir welding and cooling with water during friction stir welding of thin metal plates. In the process of submerged FSW or cooling during FSW, the maximum temperature and the time being in high temperatures will be decreased. Thus, proper grain structure, high dislocation density (in some cases), increasing of hardness, and increasing of tensile strength are the results of the process. The effect of welding parameters (like welding speed and rotation speed) on the joint properties during the welding have also been reviewed. By increasing the welding speed material, deformation and heat input will be reduced. Thus, the width of softening area decreases and the micro hardness of both TMAZ and HAZ increases. Consequently, tensile strength and elongation of the joint will be improved. If the rotation speed increases, heat input and width of softening area will be increased. In this case, although the micro hardness of TMAZ and HAZ will be reduced, the micro hardness of nugget zone will be increased. As a result, tensile strength of the welding joint will be improved, but elongation will not be changed considerably. It is noteworthy that both welding and rotation speed should not be higher than a range due to existing defects at high speeds. Using hot water as coolant would cause the best mechanical properties of the joint in compare with using other coolants.