ﺑﺮرﺳﯽ ﺗﺎﺛﯿﺮ ﺷﺮاﯾﻂ ﺣﺎﺻﻞ از اﻧﺠﻤﺎد ﺟﻬﺖدار ﺑﺮ ﺳﺎﺧﺘﺎر و ﻧﻮردﭘﺬﯾﺮي آﻟﯿﺎژ آﻟﻮﻣﯿﻨﯿﻢ 2024

Effect of Directional Solidification Conditions on the Structure and Rollability of 2024 Aluminum Alloy

ﺷﻤﺶ آﻟﯿﺎژ آﻟﻮﻣﯿﻨﯿﻢ 2024 در ﻣﻘﯿﺎس ﺻﻨﻌﺘﯽ ﺑﺎ ﮐﻨﺘﺮل دﻗﯿﻖ ﭘﺎراﻣﺘﺮﻫﺎي اﻧﺠﻤﺎدي و ﺑﮑﺎرﮔﯿﺮي دﺳﺘﮕﺎهﻫﺎي ﻣﺪرن ﺗﻮﻟﯿﺪ و ﻓﺮاﯾﻨﺪ اﮐﺴﺘﺮوژن ﺑﺮاي ﺣﺬف ﺳﺎﺧﺘﺎر رﯾﺨﺘﮕﯽ و اﻓﺰاﯾﺶ ﮐﯿﻔﯿﺖ آن ﺑﻪ ﮐﺎر ﮔﺮﻓﺘﻪ ﻣﯽﺷﻮد. در ﻣﻮاردي ﻧﺴﺒﺖ ﻫﻨﺪﺳﯽ ﻣﺤﺼﻮل اﻗﺘﻀﺎ ﻣﯽﮐﻨﺪ ﮐﻪ اﺑﻌﺎد اوﻟﯿﮥ ﺷﻤﺶ ﺑﻪ ﮐﻤﮏ ﻓﺮاﯾﻨﺪ ﻧﻮرد ﮐﺎﻫﺶ ﯾﺎﺑﺪ. ﺑﺨﺎﻃﺮ ﺗﻔﺎوتﻫﺎي ﺣﺎﻟﺖ ﺗﻨﺶ درﻧﻮرد ﺑﺎ اﮐﺴﺘﺮوژن، ﻻزم اﺳﺖ ﻋﯿﻮب در ﻓﺮاﯾﻨﺪ ﻧﻮرد ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ اﻧﺠﻤﺎد ﺧﻤﯿﺮي و ﺑﺎ داﻣﻨﻪ دﻣﺎﯾﯽ زﯾﺎد ﮐﻪ ﻣﻨﺠﺮ ﺑﻪ ﺟﺪاﯾﺶﻫﺎي ﻣﺎﮐﺮو ﺳﺎﺧﺘﺎري و رﯾﺰﺳﺎﺧﺘﺎري ﻣﯽﺷﻮد، ﺑﺮرﺳﯽ ﺷﻮد. ﻫﺪف از اﯾﻦ ﺗﺤﻘﯿﻖ اﯾﺠﺎد اﻧﺠﻤﺎد ﺟﻬﺖدار، ﮐﻨﺘﺮل اﻧﺠﻤﺎد ﺧﻤﯿﺮي و ارﺗﻘﺎ ﻧﻮرد ﭘﺬﯾﺮي اﺳﺖ. ﺟﻬﺖ دﺳﺖﯾﺎﺑﯽ ﺑﻪ اﻧﺠﻤﺎد ﺟﻬﺖدار ﺑﺮاي از ﺑﯿﻦ ﺑﺮدن ﻧﻘﺺﻫﺎي رﯾﺨﺘﻪﮔﺮي، ﺑﺮﻗﺮاري ﮔﺮادﯾﺎن ﺣﺮارﺗﯽ ﺑﯿﻦ ﺗﻐﺬﯾﻪ و ﻣﺒﺮد اﻧﺠﺎم ﺷﺪ و اﺛﺮ ﻋﻤﻠﯿﺎت ﻣﺤﻠﻮﻟﯽ T4 ﺑﺮ رﯾﺰﺳﺎﺧﺘﺎر ﺷﻤﺶ اﻣﮑﺎن ﺟﻠﻮﮔﯿﺮي از ﻧﻮاﻗﺺ ﻧﻮردي ﻣﺎﻧﻨﺪ ﺗﺮك دﻫﺎن ﺗﻤﺴﺎﺣﯽ ﺑﺮرﺳﯽ و ﺑﻪ ﮐﻤﮏ ﺷﺒﯿﻪﺳﺎزي ﺗﺼﺤﯿﺢ ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ ﻧﺴﺒﺖ ﻣﺪول ﺗﻐﺬﯾﻪ ﺑﻪ ﻗﻄﻌﻪ 0/35 و اﺳﺘﻔﺎده از ﻣﺒﺮد، ﻣﯽﺗﻮان ﺑﺎ اﻧﺠﻤﺎد ﺟﻬﺖدار ﻋﯿﻮب رﯾﺨﺘﮕﯽ را ﺑﻪ ﺣﺪاﻗﻞ ﻣﻘﺪار ﻣﻤﮑﻦ رﺳﺎﻧﺪ. ﺑﺮرﺳﯽ ﻣﺎﮐﺮو ﺳﺎﺧﺘﺎر و رﯾﺰﺳﺎﺧﺘﺎر ﻧﻤﻮﻧﻪﻫﺎ ﻗﺒﻞ و ﺑﻌﺪ از اﻧﺠﺎم ﻋﻤﻠﯿﺎت ﻣﺤﻠﻮﻟﯽ ﻧﺸﺎن داد ﮐﻪ ﺗﻔﺎوت ﭼﺸﻤﮕﯿﺮ در اﻓﺰاﯾﺶ ﻫﻤﮕﻨﯽ ﺑﻪ ﮐﻤﮏ ﻋﻤﻠﯿﺎت ﺣﺮارﺗﯽ ﻗﺎﺑﻞ ﺣﺼﻮل اﺳﺖ. ﺳﺨﺘﯽ ﻧﻤﻮﻧﻪ ﻋﻤﻠﯿﺎت ﻣﺤﻠﻮﻟﯽ ﺷﺪه، 30 درﺻﺪ از ﻧﻤﻮﻧﻪ رﯾﺨﺘﻪﮔﺮي ﺷﺪه ﮐﻤﺘﺮ ﺑﻮده ﮐﻪ ﺑﺪﻟﯿﻞ رﺷﺪ داﻧﻪ ﭘﺲ از ﻋﻤﻠﯿﺎت ﺣﺮارﺗﯽ و از ﺑﯿﻦ رﻓﺘﻦ ﻓﺎزﻫﺎي ﺑﯿﻦﻓﻠﺰي ﺑﺎ ﺳﺨﺘﯽ ﺑﯿﺸﺘﺮ اﺳﺖ. اﻣﮑﺎن ﺑﻬﺒﻮد ﻗﺎﺑﻠﯿﺖ ﻧﻮرد ﭘﺬﯾﺮي و ﺟﻠﻮﮔﯿﺮي از ﻋﯿﻮب ﻧﻮرد ﺑﻪوﯾﮋه ﻋﯿﺐ دﻫﺎن ﺗﻤﺴﺎﺣﯽ، ﺑﺎ ﺗﺪاﺑﯿﺮ اﺗﺨﺎذ ﺷﺪه اﻣﮑﺎنﭘﺬﯾﺮ اﺳﺖ.

The 2024 aluminum alloy slab is usually produced at industrial scale with precise control on the solidification parameters using modern machines and undergoing extrusion process after casting in to eliminate the casting structure and increase the quality of the slab. The purpose of this research is to provide directional solidification in the 2024 aluminum alloy slab to control the mushy solidification and improve the rollability. For this reason directional solidification is used to eliminate the casting defects and to obtain thermal gradient between the riser and chiller. After studying on the effect of solution treatment T4 on the microstructure of the produced slab the possibility of avoiding rolling defects such as alligator cracking was studied and was optimized using simulation. The obtained results showed that with the feeder/sample ratio of 0.35 and the use of a suitable chiller, the directional solidification of Al2024 alloy can be obtained with minimum casting defects. Also study on the macrostructure and microstructure before and after solution treatment showed that a significant difference in the increase of the homogenization can be obtained by applying the applied thermal treatment. Furthermore the hardness of the solution treated sample is 30 percent less than of the as-cast sample which is due to the grain growth after thermal treatment and the elimination of the intermetallic phases of higher hardness. Also it was shown that the possibility of improving the rollability and avoiding rolling defects specially alligator cracking is possible using the suitable conditions of directional solidification and thermal solution.