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Fabrication of AA7075 Thin Plates for PEM Fuel Cells by Thixoforging
Amir Bolouri(아미르),Chang Hyun Jang(장창현),Chung Gil Kang(강충길) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Aluminum 7075 alloy extrusion billets have been used as the feedstock for thixoforging of thin plates. Recrystallisation and remelting (RAP) route has been employed to prepare the semisolid slurries. A direct die-filling system was designed for thixoforging of thin plate. Thin plates were thixoforged at the temperatures of 610℃, 615℃ and 620℃ with application of 70 MPa forging pressure. The quality of thin plates was examined by X-ray radiography. Hot tearing defects were detected when thixoforging was conducted at higher temperatures. The elongated grains in the initial extrusion billets were transferred to the globular grains within the semisolid slurry. However, some interconnected grains were observed. The microstructure of thixoforged thin plates indicated that a disagglomeration effect was active during thixoforging.
틱소 성형공정에서 알루미늄 7075 소재성분의 분산거동
아미르 불로울리(Amir Bolouri),모하마드 샤미르(Mohammad Shahmiri),강충길(C.G. Kang) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
There is a strong drive to near net shape forming of 7075 series aluminum alloys, which are currently machined from the wrought state with much waste. Semisolid processing is one potential near net shaping route which involves processing metallic alloys between the solidus and the liquidus. Thixo-forming route (applicable to 7xxx series) derives great benefit from the thixotropic behavior in the semisolid state of alloys. In this study, the feed stock for the Thixo-forming process of A1 7075 alloy was investigated. The feed stock was fabricated by means of Strain Induced Melt Activation (SIMA) process. The alloying elements distribution and segregation of the samples were thoroughly examined by energy-dispersive X-ray (EDX) spectroscopy for different temperatures and soaking times in the semisolid state. The results revealed that at the high soaking temperatures 620℃ and 6250℃ the alloying segregation happened after 15min and 10min soaking time, respectively, while for the low temperatures (590-610℃) there was no evidence of alloying segregation at prolonged soaking time (20 min). The possible effects of alloying elements segregation on the final mechanical properties as well as the required post-formed treatments were completely discussed.
Thixoforming of AI7075 Alloy with High Solid Fraction
Amir Bolouri(아미르 볼루리),Chang Hyun Jang(장창현),Mohammad Shahmirl(모하메드 샤미리),Chung Gil Kang(강충길) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
Aluminum 7075 alloy has been used as the feedstock for thixoforming in order to investigate the thixoformability of the alloy at high solid fratcions. Strain induced melting activation (SIMA) route has been employed to prepare the alloy to behave as the thixotropic material when reheated into the semisolid state. The results of reheating experiments at 590℃, 600℃ and 610℃ corresponding to high slid fractions (above 0.75) are presented. The reheating experiments were conducted for various holding times: 10min, 15min and 20min. According to the microstructure was achieved. Thixforming experimental at 590℃ failed. At 610℃, the optimum forming condition obtained for 300kN and 400kN at 0.75m/s ram speed.