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بررسي تاثير دمش گاز خنثي در فرآيند نيمه جامد كامپوزيت Al-20%Mg2Si بر ريز ساختار و خواص مكانيكي

كارشناسي ارشد

مهندسي مواد و متالورژي

1399

1401/12/20

دكتر سعيد شبستري

مهندسي مواد و متالورژي

فرآيند ريخته‌گري نيمه جامد با تكنيك دمش گاز خنثي GISS)) از روش هاي نويني محسوب مي‌شود كه براي ريخته‌گري آلياژ هايي با دامنه انجماد طولاني به منظور تشكيل ريز ساختار گلبولي و كروي گسترش يافته است. در اين فرآيند لوله گرافيتي متخلخل در دمايي بالاتر از دماي منحني مايع آلياژ درون مذاب قرار گرفته و عمليات دمش گاز خنثي با دبي و مدت زمان دمش معين انجام مي‌‌گيرد و سپس عمليات شكل دهي بر روي مخلوط جامد- مذاب حاصل از اين روش انجام ‌مي‌شود. يكي از مواد مورد نظر براي انجام فرآيند GISS كامپوزيت هاي درجاء Al-Mg2Si هستند كه به دليل خواص مكانيكي و سايشي مناسب امروزه بسيار مورد توجه صنايع قرار گرفته است ولي وجود ذرات Mg2Si اوليه با مورفولوژي خشن و دندريتي از نقاط ضعف اين مواد به شمار مي‌رود. در پژوهش حاضر براي اولين بار تاثير فرآيند دمش گاز خنثي آرگون در دما، زمان و دبي هاي مختلف بر ريز ساختار و خواص مكانيكي كامپوزيت Al-20%Mg2Si مورد بررسي قرار گرفت و همچنين عمليات دمش گاز خنثي به منظور مشخص شدن تاثير افزايش محل هاي ورود گاز خنثي به مذاب توسط يك و دو دمنده به صورت جداگانه روي يك نمونه ثابت انجام شد و در شرايط مختلف فرآيند تعداد 16 عدد نمونه ريخته‌گري شد . بررسي نتايج آناليز تصويري نشان مي‌دهد كه براي نمونه بهينه توليد شده در دماي 660 درجه‌ سانتي گراد با دبي دمش 6 ليتر بر دقيقه توسط دو دمنده گرافيتي به مدت زمان 20 ثانيه، ميانگين اندازه ذرات 32 ميكرومتر، ميزان كرويت 65% و تعداد ذرات 405 عدد در ميلي‌متر مربع حاصل شده است كه در مقايسه با نمونه شاهد بهبود قابل توجهي بدست آمده است. همچنين با بررسي نتايج آزمون سختي و آزمون كشش مي‌توان دريافت كه ميزان سختي براي نمونه بهينه 32%، استحكام كششي نهايي 18%، درصد ازدياد طول نسبي 39%، انرژي مخصوص لازم تا نقطه شكست 66% و استحكام تسليم به ميزان 12% نسبت به نمونه شاهد افزايش داشته است.

1402/01/26

Effect of Inert Gas Induced Semi Solid Process of Al-20%Mg2Si Composite on the Microstructure and Mechanical Properties

3/10/2024 12:00:00 AM

The semi-solid casting process with the inert gas blowing technique (GISS) is one of the new methods that has been developed for casting alloys with a long solidification range in order to forming globular and spherical microstructures. In this process, the porous graphite tube is subjected into the higher temperature melt with respect to the liquid curve temperature of the alloy, consequently, the inert gas blowing operation is performed with a certain flowing rate and certain blowing duration. Finally, the mentioned procedures will be followed by forming operation which is applied on the solid-melt mixture resulting from this method. One of the desired materials for performing the GISS process is Al-Mg2Si composite, This material have received a lot of attention in the industry due to their suitable mechanical and wear properties, however, the presence of primary Mg2Si particles with rough and dendritic morphology is one of the weak points of these materials. In this study, for the first time, by considering different temperatures, time and flow rates, the effect of Argon inert gas blowing process has been investigated on the microstructures and mechanical properties of Al-20%Mg2Si composite. Also, for blowing gas into the melt, we used one or two diffusers separately (On the other hand, for example, we puted one diffuser in mellt and at the other time we puted both diffusers in the melt), Therefore, the effect of such increasing in (GISS) has been investigated in our study. The described procedure was accomplished on 16 samples with one diffuser and just for one fixed sample the method applied with one and two diffusers. Careful study of the obtained results of image analysis shows that the sphericity rate of microstructures has been acceded to 65% and the number of particles has been approached to 405 in one square millimeters, which these properties have been significantly improved compared to the blank sample. For this investigation, we used optimal sample which associated temperature was 660 degrees Celsius. This sample was subjected to two graphite diffusers with blowing flow rate equals to 6 liters per minutes. Also, the duration of the aforementioned blowing rate considered as 20 seconds and average particle size was 32 micrometers. Also, by examining the results of the hardness test and tensile test, and comparing the results of this study with blank sample, it can be seen that the hardness level for the optimal sample has been increased 32 percentage, the ultimate tensile strength has been increased 18 percentage, the percentage of relative elongation has been increased 39 percentage, the specific energy required to the fracture point has been increased 66 percentage and the yield strength is has been increased 12 percentage

كامپوزيت درجاء , ريزساختار كروي و گلبولي , روش دمش گاز خنثي , فرآيند نيمه جامد

Al-20%Mg2Si , GISS , semi solid , inert gas indused

ahad nasimi asl

saeed shabestari