This study evaluated the mechanical joining characteristics of substrate Al7075 using the filler metals of ER5356 and Al7075 to secure the joining integrity of the specimens by GTAW. The results of radiographic test show that the welded specimens meet the first level standard of KS D 2042. Besides, welding defects were not occurred. The tensile strengths of the specimens using the filler metals of Al7075 and ER5356 had 240MPa and 252MPa, respectively. The yield strengths were 132MPa and 120MPa, respectively. In case of using the filler metal of Al7075, However, in case of using the filler metal of ER5356, Two filler metals of Al7075 and ER5356 were similar to each other in tensile and yield strength.

In this study, the effect of wear resistance was investigated in Al 7075 alloys. For this purpose, three wear factor which are wear loss, coefficient of friction and friction forec applied to test wear-resistance. Wear test of ball-on-disk has been performed using steel balls to determine the variation of wear characteristics. Finally, the coefficient of wear was calculated by the Archard wear equation in Al 7075 alloys.

In this work, ceramic coatings were prepared on Al7075 aluminum alloy using microarc oxidation (MAO) process in a silicate-fluoride based electrolyte solution. The effect of OH− concentration, by adding NaOH to the solution on the microstructural and mechanical properties of the coating was investigated. Surface morphology and cross sectional view of the coating was analyzed using SEM while XRD was used to examine the phase compositions of the coatings. From XRD α-Al2O3 phase was found to be increased by adding NaOH to the electrolyte. Thereby, the hardness and the wear properties of the MAO coatings were found to be superior to those of the coatings prepared without NaOH addition or with amount maximum than 2 g/l NaOH. Moreover, the morphology of the coatings was transformed form nodule-based cluster to crater based structure with the addition of NaOH to the MAO electrolyte solution.

가공열처리한 7075Al합금을 170˚C에서 퇴화처리하여도 GP대는 완전히 분해되지 않았으며 초기의경도저하는 부분적인 GP대의 분해에 기인하고 μ '의 생성으로 강도는 증가하다가 μ '의 성장 및 μ의 생성으로 강도는 다시 저하한다. 퇴화처리시 경도 곡선의 극소점이나 2차 피크점(극대점)에서 RRA처리한 시편의 응력부식 특성은 T6재에 비하여 상당히 개선되며 강도의 저하를 수반하지 않는다. 또한 저온인 170˚C에서 퇴화처리시 기지조직의 변화가 크지 않아 퇴화처리시 경도곡도의 극소점과 2차 피크점에서의 특성차이는 거의 없었다.

Recently, study on the application of sustainable materials to building and civil structure fields has been increased. Especially, the usage of aluminum alloys can improve durability of structures due to it’s high corrosion resistance. In this study, to investigate the ultimate behaviors such as ultimate strength and fracture mode of single shear bolted connections with aluminum alloys (7075-T6), experiments were conducted. Main variables are bolt arrangement and end distance parallel to the direction of load. As a result, the specimens failed by shear out fracture and block shear fracture and also the specimens with long end distance were accompanied by curling (out of plane deformation). The curling led to reduction of ultimate strength or rigidity. Futhermore, pattern of strain distribution was investigated according to curling occurrence.