학술논문
이(異)종 층상 Al합금의 반복겹침접합압연법에 따른 미세조직 및 기계적 특성 변화 분석 / Microstructure and Mechanical Properties of Three Dissimilar Aluminium Alloys by Accumulative Roll-Bonding Process
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
ARB(Accumulative Roll Bonding)공정은 금속판재를 반복적으로 겹치기 압연하여 결정립 초미세화와 고강도를 달성하는 효과적인 강소성가공법 중 하나이다. 이번 연구에서는 각기 다른 이(異)종 알루미늄(AA1050, AA6061, AA5052)을 ARB공정을 이용해 다층으로 적층하여 복합판재의 제조에 성공하였다. 이 복합판재의 미세조직과 기계적 특성을 평가하기 위해 OM(Optical Microscope), SEM(Scanning Electron Microscope), EBSD(Electron Backscatter Diffraction), tensile test, erichsen test를 진행하였다. 또한 결정을 이용하여 강도와 연신율의 비례를 타진하기 위해 전기로를 이용 200℃, 250℃, 275℃, 300℃, 350℃, 375℃, 400℃, 450℃, 500℃까지 30분 동안 annealing하여 실험을 진행하였다. 가공경화의 효과로 강도를 높이고 순알루미늄의 효과로 연신을 높이고자 시행한 AA5052/AA1050 2layer에서 강도는 높게 나왔으나 연신이 현저히 감소한 결과를 나타내었다. 열처리를 통해 bimodal structure의 가능성을 보았으나, 강도가 떨어지는 현상을 보였다. 부족한 연신을 높이기 위해 AA1050을 추가하여 3layer로 실험을 진행하였다. 연신은 약간 증가하였지만, 강도가 약간 떨어지는 현상을 보였고, 열처리과정 중 더욱 급격한 강도의 감소를 나타냈었다. 강도와 연신을 동시에 타진하고자 4layer로 실험을 진행하였다. 강도와 연신이 약간 증가하였지만, 본 연구의 목적을 달성하기에는 미비한 결과를 나타내었다. 열처리를 통해 bimodal structure를 만드는데 성공하였지만, 강도와 연신을 동시에 타진 할 수 없었다. 열처리를 통한 석출경화의 효과를 보고자 AA6061/AA1050을 4layer로 시행하였을 때, 열처리 과정을 통해 bimodal structure를 만드는데 성공하였지만, 적층된 판재의 수가 적고, 적합한 열처리 조건을 찾지 못해 강도와 연신율을 동시에 타진하지 못하였다. 세가지의 알루미늄 합금을 사용하여 4layer로 진행한 실험에서 각기 다른 재결정을 통해 이번 연구의 목적인 bimodal structure를 갖는 복합판재 제조에 성공하였고, 강도와 연신을 모두 증가시키는 결과를 얻을 수 있었다.
Accumulative roll-bonding (ARB), a unique technique developing an ultrafine grained (UFG) structure, is mostly favorable for practical applications because it could be readily performed by conventional rolling machine. In this study, each of different Al such as, AA1050, AA6061, AA5052 was differently stacked a multlayers and the hard sheet material adapted to produce a composite sheet is applied to the different layers. The composite layers were analyzed by OM(Optical Microscope), SEM(Scanning Electron Microscope), EBSD(Electron Backscatter Diffraction), tensile test and erichsen test. By using an electric furnace annealing at 200℃, 250℃, 275℃, 300℃, 350℃, 375℃, 400℃, 450℃, 500℃ to determine the proportion of the strength and elongation using a crystal was treated for 30 minutes. At AA5052/AA1050 2layers which was carried out to increase the strength by work hardening and elongation by the effect of pure aluminum, the strength was increased and elongation was sharply decreased. There’s a little chance of bimodal structure through the heat treatment, but the strength was decreased. To improve the lack of the elongation, the test was carried out by 3layers adding AA1050. Elongation was slightly increased but the strength was decreased. And strength decreased slightly during the heat treatment process. The experiment to increase the strength and elongation was carried out by 4layers. Although the strength and elongation, increased slightly, it was not good enough to reach the goal of the study. Although we succeeded in fabricating a bimodal structure through heat treatment. But the strength and elongation could not be improved at the same time. When AA6061/AA1050 was carried out by 4layers for the effect of the precipitation hardening through heat treatment. We succeeded in fabricating a bimodal structure through heat treatment. But the strength and elongation could not be improved at the same time. Because the stacked sheet was small in number and the condition of the heat treatment was not suitable. Therefore, in this study of using three different Al alloy 4layers, we succeeded in fabricating bimodal structure composite sheet, and we made it successful to increase was of the strength and elongation.
Accumulative roll-bonding (ARB), a unique technique developing an ultrafine grained (UFG) structure, is mostly favorable for practical applications because it could be readily performed by conventional rolling machine. In this study, each of different Al such as, AA1050, AA6061, AA5052 was differently stacked a multlayers and the hard sheet material adapted to produce a composite sheet is applied to the different layers. The composite layers were analyzed by OM(Optical Microscope), SEM(Scanning Electron Microscope), EBSD(Electron Backscatter Diffraction), tensile test and erichsen test. By using an electric furnace annealing at 200℃, 250℃, 275℃, 300℃, 350℃, 375℃, 400℃, 450℃, 500℃ to determine the proportion of the strength and elongation using a crystal was treated for 30 minutes. At AA5052/AA1050 2layers which was carried out to increase the strength by work hardening and elongation by the effect of pure aluminum, the strength was increased and elongation was sharply decreased. There’s a little chance of bimodal structure through the heat treatment, but the strength was decreased. To improve the lack of the elongation, the test was carried out by 3layers adding AA1050. Elongation was slightly increased but the strength was decreased. And strength decreased slightly during the heat treatment process. The experiment to increase the strength and elongation was carried out by 4layers. Although the strength and elongation, increased slightly, it was not good enough to reach the goal of the study. Although we succeeded in fabricating a bimodal structure through heat treatment. But the strength and elongation could not be improved at the same time. When AA6061/AA1050 was carried out by 4layers for the effect of the precipitation hardening through heat treatment. We succeeded in fabricating a bimodal structure through heat treatment. But the strength and elongation could not be improved at the same time. Because the stacked sheet was small in number and the condition of the heat treatment was not suitable. Therefore, in this study of using three different Al alloy 4layers, we succeeded in fabricating bimodal structure composite sheet, and we made it successful to increase was of the strength and elongation.