بررسي ريزساختار و خواص مكانيكي آلياژ 5083 Al توليد شده به روش انجماد سريع

Microstructure and mechanical properties of Al 5083 alloy produced by rapid solidification

ﺳﺎﺧﺘﺎر ﺟﺎﻣﺪات ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﭘﺎراﻣﺘﺮﻫﺎي اﻧﺠﻤﺎد ﻣﺨﺼﻮﺻﺎ ﺳﺮﻋﺖ ﺳﺮدﮐﺮدن و ﺗﺤﺖ ﺗﺒﺮﯾﺪ ﻗﺮار دارد. ﺑﻪ ﺧﻮﺑﯽ ﻣﺸﺨﺺ ﺷﺪه اﺳﺖ ﮐﻪ ﺳﺮﻋﺖ اﻧﺠﻤﺎد ﻧﻘﺶ ﻣﻬﻤﯽ در زﻣﯿﻨﻪ اﺻﻼح ﺳﺎﺧﺘﺎر ﻓﻠﺰات ﺑﺎزي ﻣﯽﮐﻨﺪ و در ﻧﺘﯿﺠﻪ ﻗﻮﯾﺎ روي ﺧﻮاص ﻣﮑﺎﻧﯿﮑﯽ ﺗﺎﺛﯿﺮ ﺧﻮاﻫﺪ ﮔﺬاﺷﺖ. در ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ از روش ﻣﺬاب رﯾﺴﯽ ﺟﻬﺖ اﯾﺠﺎد ﺳﺮﻋﺖ ﺑﺎﻻي ﺳﺮد ﮐﺮدن ﻣﺬاب و ﺗﻮﻟﯿﺪ ﻧﻤﻮﻧﻪ ﻫﺎي ﻧﻮاري ﺷﮑﻞ در آﻟﯿﺎژ آﻟﻮﻣﯿﻨﯿﻢ5083 اﺳﺘﻔﺎده ﺷﺪ. ﺳﭙﺲ، ﺧﻮاص و رﯾﺰﺳﺎﺧﺘﺎر ﺑﻪ دﺳﺖ آﻣﺪه ﺑﺎ اﺳﺘﻔﺎده از ﻣﯿﮑﺮوﺳﮑﻮپ ﻧﻮري، ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯽ روﺑﺸﯽ )SEM(، ﭘﺮاش اﺷﻌﻪ(XRD) x و ﻣﯿﮑﺮوﺳﺨﺘﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﻧﺘﺎﯾﺞ ﺑﻪ ﺧﻮﺑﯽ ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ ﺳﺮﻋﺖ ﺑﺎﻻي ﺳﺮد ﮐﺮدن در اﯾﻦ روش از ﻃﺮﯾﻖ ﺗﺸﮑﯿﻞ ﻓﺎزﻫﺎي ﮐﺮوي ﺷﮑﻞ ﺑﯿﻦ ﻓﻠﺰي و ﻏﻨﯽ از آﻫﻦ، ﻣﻨﮕﻨﺰ، ﻣﻨﯿﺰﯾﻢ و ﺳﯿﻠﯿﺴﯿﻢ ﺑﺎ اﺑﻌﺎد ﻧﺎﻧﻮ )ﺗﺎ 50 nm( ﮐﻪ ﺑﻪ ﻃﻮر ﯾﮑﻨﻮاﺧﺖ در رﯾﺰﺳﺎﺧﺘﺎر ﺗﻮزﯾﻊ ﺷﺪه اﻧﺪ و ﻫﻤﭽﻨﯿﻦ اﺳﺘﺤﮑﺎم ﺑﺨﺸﯽ ﻣﺤﻠﻮل ﺟﺎﻣﺪ ﻧﺎﺷﯽ از اﻓﺰاﯾﺶ ﺣﺪ ﺣﻼﻟﯿﺖ ﻋﻨﺎﺻﺮ در ﻓﺮآﯾﻨﺪ اﻧﺠﻤﺎد ﺳﺮﯾﻊ، ﺳﺒﺐ اﺻﻼح رﯾﺰﺳﺎﺧﺘﺎر و در ﻧﺘﯿﺠﻪ ﺑﻬﺒﻮد ﺧﻮاص ﻣﮑﺎﻧﯿﮑﯽ ﻧﻤﻮﻧﻪ ﻫﺎي ﻣﺬاب رﯾﺴﯽ ﺣﺎﺻﻞ در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﻓﺮآﯾﻨﺪﻫﺎي ﻣﻌﻤﻮل رﯾﺨﺘﻪ ﮔﺮي ﻣﯽﺷﻮد. ﺑﻪ ﻃﻮري ﮐﻪ ﻣﯿﺰان ﺳﺨﺘﯽ ﻧﻮارﻫﺎي ﻣﺬاب رﯾﺴﯽ ﻧﺴﺒﺖ ﺑﻪ ﻧﻤﻮﻧﻪ ﺣﺎﺻﻞ از روش ﻫﺎي ﻣﻌﻤﻮل رﯾﺨﺘﻪ ﮔﺮي ﺑﻪ ﻣﯿﺰان ﺑﯿﺶ از دو ﺑﺮاﺑﺮ اﻓﺰاﯾﺶ ﻧﺸﺎن ﻣﯽدﻫﺪ.

The structure of metals strongly depends on solidification parameters such as cooling rate and supercooling. It is obvious that the cooling rate is an important factor in order to refine metal structure, and especially affecting mechanical properties of metals. In this investigation melt spinning method is used to reach rapid solidification and ribbon shaped samples in Aluminum 5083 alloy were produced. The resulting ribbon samples were studied by optical microscopy (OM), scanning electron microscopy (SEM), micro hardness tester, X-ray difractometry, and were compared with their ingot counterparts. The results perfectly shown that the produced ribbons exhibits unique properties such as enhanced solid-solubility level of elements in the Al matrix (solid solution strengthening) and formation of spherically shaped intermetallic phases rich in Fe, Mn and Si and less than 50 nm in size homogenously dispersed in Al matrix which resulted in mechanical properties improvement and microstructural refinement of Al5083 alloy. As an example microhardness was approximately raised over 2 times more than conventional casting methods.