بررسي ريزساختار و خواص مكانيكي آلياژهاي Al-2Ni-xMn به عنوان جايگزين آلياژ هيپويوتكتيك Al-4Ni

Investigation of microstructure and mechanical properties of Al-2Ni-xMn alloys as substitute for hypoeutectic Al-4Ni alloy

ر ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ، رﯾﺰﺳﺎﺧﺘﺎر و ﺧﻮاص ﻣﮑﺎﻧﯿﮑﯽ آﻟﯿﺎژﻫﺎي Al-2Ni-xMn ﺑﻪﻋﻨﻮان ﺟﺎﯾﮕﺰﯾﻦ آﻟﯿﺎژﻫﺎي ﻫﯿﭙﻮﯾﻮﺗﮑﺘﯿﮏ Al-4Ni ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺪﯾﻦ ﻣﻨﻈﻮر ﻧﻤﻮﻧﻪﻫﺎي ﻣﺬاب ﺣﺎوي 2 درﺻﺪ وزﻧﯽ ﻧﯿﮑﻞ و 2 ،1 و 4 درﺻﺪ وزﻧﯽ ﻣﻨﮕﻨﺰ ﺗﻬﯿﻪ ﺷﺪه و ﺗﺤﺖ دو ﺳﺮﻋﺖ ﻣﺘﻔﺎوت )3/5 و 10/4 درﺟﻪ ﺳﺎﻧﺘﯿﮕﺮاد ﺑﺮ ﺛﺎﻧﯿﻪ( ﻣﻨﺠﻤﺪ ﺷﺪﻧﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ ﺑﻪدﺳﺖ آﻣﺪه، در ﺳﺮﻋﺖ اﻧﺠﻤﺎد ﮐﻢ، اﺳﺘﺤﮑﺎم ﮐﺸﺸﯽ، ﮐﺮﻧﺶ ﺷﮑﺴﺖ و ﭼﻘﺮﻣﮕﯽ آﻟﯿﺎژ Al-2Ni-1Mn ﺑﻪ ﺗﺮﺗﯿﺐ ﺣﺪود 115 ،26 و 137 درﺻﺪ ﺑﯿﺶ از ﺧﻮاص ﻣﺬﮐﻮر در آﻟﯿﺎژ Al-4Ni اﺳﺖ، اﻣﺎ اﻓﺰودن ﻣﻘﺎدﯾﺮ ﺑﯿﺸﺘﺮ ﻣﻨﮕﻨﺰ، ﻣﻮﺟﺐ اﻓﺖ ﺧﻮاص ﮐﺸﺸﯽ ﻣﯽﺷﻮد. ﺑﺎ اﻓﺰاﯾﺶ ﺳﺮﻋﺖ اﻧﺠﻤﺎد، ﺑﻪ واﺳﻄﻪ ﮐﺎﻫﺶ اﺑﻌﺎد و ﺗﻮزﯾﻊ ﻣﻨﺎﺳﺐ رﺳﻮﺑﺎت ﺑﯿﻦﻓﻠﺰي ﻏﻨﯽ از ﻧﯿﮑﻞ و ﻣﻨﮕﻨﺰ و ﺗﺨﻠﺨﻞﻫﺎ در رﯾﺰﺳﺎﺧﺘﺎر، ﮐﺎﻫﺶ ﻓﺎﺻﻠﻪ ﺑﯿﻦ ﺑﺎزوﻫﺎي ﺛﺎﻧﻮﯾﻪ دﻧﺪرﯾﺘﯽ و اﻧﺪازه داﻧﻪﻫﺎ، ﺧﻮاص ﻣﮑﺎﻧﯿﮑﯽ آﻟﯿﺎژﻫﺎي ﻏﻨﯽ از ﻣﻨﮕﻨﺰ ﺑﻪﻣﯿﺰان ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪاي ﺑﻬﺒﻮد ﻣﯽﯾﺎﺑﺪ. ﺑﻬﺘﺮﯾﻦ ﺧﻮاص ﮐﺸﺸﯽ ﻣﺮﺑﻮط ﺑﻪ ﻧﻤﻮﻧﻪ Al-2Ni-1Mn رﯾﺨﺘﻪﮔﺮي ﺷﺪه در ﻗﺎﻟﺐ ﻣﺴﯽ اﺳﺖ ﮐﻪ در آن اﺳﺘﺤﮑﺎم ﮐﺸﺸﯽ، ﮐﺮﻧﺶ ﺷﮑﺴﺖ و ﭼﻘﺮﻣﮕﯽ ﺑﻪ ﺗﺮﺗﯿﺐ 200 ،50 و 330 درﺻﺪ ﺑﯿﺶ از ﺧﻮاص ﻣﺬﮐﻮر در آﻟﯿﺎژ Al-4Ni ﻣﻨﺠﻤﺪ ﺷﺪه ﺗﺤﺖ ﺳﺮﻋﺖ 3/5 درﺟﻪ ﺳﺎﻧﺘﯿﮕﺮاد ﺑﺮ ﺛﺎﻧﯿﻪ اﺳﺖ.

In the current study the microstructure and mechanical properties of Al-2Ni-xMn alloys was investigated as a substitute for Al-4Ni alloys. To this end, different melts containing 2 wt. % Ni and 1, 2, and 4 wt. % Mn were solidified at two cooling rates of 3.5 and 10.4 C/s. According to the results, under the low solidification rate, the tensile strength, fracture strain, and toughness of Al-2Ni-1Mn alloy are lower than those of Al-4Ni alloy by 26, 115, and 137%, respectively. However, further Mn addition impaired the tensile properties. Increasing the solidification cooling rate decreases the size and improves the distribution of Ni(Mn)-rich compounds and porosities within the microstructure and reduces the sizes of secondary dendrite arm spacing and grains. This substantially improved the mechanical properties of Mn-rich alloys. For instance, compared to Al-4Ni alloy solidified at 3.5 C/s, the tensile strength, fracture strain, and toughness of copper mold cast Al-2Ni-1Mn alloy increased by 50, 200, and 330%, respectively.