Behavior of different welded joints for al-alloy (6061-t6)‎ in erosive-corrosive environments

مقدم أطروحة جامعية

Abd, Hasan Hadi

مشرف أطروحة جامعية

Abbas, Muna Khathir

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة الإنتاج و المعادن

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2012

الملخص الإنجليزي

Aluminum alloys (6XXX series) are widely used in the structural components of automotive and construction industries as they show a good combination of formability, corrosion resistance, weldability, and final mechanical properties.

In this study two different welding processes have been considered: a conventional tungsten inert gas (TIG) and a relatively new solid state welding known as friction stir welding.

TIG welding process has been performed on Al 6061-T6 of thickness 4mm by using filler metal of Al-Mg alloy type (ER5356) according to AWS classifica on metal with tungsten electrode (EWth-2) and arc voltage of (12V).

Various welding currents of (125, 160, 200, 225) Amp were used under argon as shielding gas of flow rate of (15-20 cf / h) and welding speed of 280 mm/min.

Friction stir welding is carried out using automatic milling machine under five different welding speeds of (25-50-80-100-125 mm/min) and five different tool rota on speeds of (630-800-1000-1250-1600 rpm).

Tool steel of type R18 consists of a shoulder with diameter of (20 mm) and pin of diameter (5.5 mm).

X-ray radiographic inspection, tensile test and microhardness test of FSW and TIG joints at optimum welding conditions were made.

The results indicate that the tensile strength of FSW joints is 289 MPa and joint efficiency is 79% which were welded with welding parameters of (1250 rpm, 800 rpm and 50 mm/min, 125 mm/min) respec vely.

While in case of TIG joint the tensile strength was 210 MPa and joint efficiency was 57%.

It was found that the hardness values in the TIG welded joints are lower than that of the FSW joints.

The formation of fine, equiaxed grains and uniformly distributed, very fine strengthening precipitates (Mg₂Si) in the weld region are the reasons for higher tensile strength and hardness of FSW joints compared to TIG joints.

Erosion-corrosion tests with and without slurry were carried out in 3.5wt % NaCl solu on and slurry solu on of (3.5wt % NaCl +1wt % SiO2 as erodent) respec vely were made to study the behavior of TIG and FSW welded joints in different corrosive environments.

Erosive – corrosive medium was injected at Q = 36 L / min and pressure of 1 bar and impact angle of 90⁰.

Free corrosion test was carried out in 3.5wt % NaCl solu on by recording open circuit potential (OCP) after immersion the sample, the first potential was allowed to stabilize and then a er (1 hour) immersion, the test was stopped.

It was found that erosioncorrosion rate (gmd) of base alloy Al 6061-T6 is lower than that of welded joints samples, and erosion-corrosion rate (gmd) in the slurry solution is higher than that in solution without slurry for all samples base alloy and welded joints (FSW, TIG).

From OCP-time measurement with respect to SCE (Standard Calomel Electrode) a er immersion in 3.5wt % NaCl solu on at 25 C⁰, it was found that all welded joints (FSW, TIG) have the free corrosion potential less negative (less suscepitability to corrosion) than the base alloy (Al 6061-T6) in 3.5wt % NaCl solu on.

التخصصات الرئيسية

العلوم الهندسية والتكنولوجية (متداخلة التخصصات)

الموضوعات

• الخواص الميكانيكية
• سبائك الألومنيوم

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-419957