【摘要】：過共晶Al-Si合金具有熱膨脹系數(shù)小、熱穩(wěn)定性好、低密度、高硬度、耐高溫、耐磨等特點,在發(fā)動機零部件等領(lǐng)域具有較好的應(yīng)用前景。對于過共晶Al-Si合金而言,通常采用變質(zhì)處理的方法來細化初生硅。眾多的變質(zhì)處理方法中,P變質(zhì)細化初生硅效果明顯且穩(wěn)定、易行。含P中間合金加入到過共晶Al-Si合金熔體后,需要對熔體進行攪拌才能獲得較好的變質(zhì)處理效果,但是,攪拌的程度對變質(zhì)處理效果有何影響規(guī)律并不清楚。本文以Al-15%Si合金、Al-18%Si合金、Al-20%Si合金為研究對象,采用Cu-9%P合金進行變質(zhì)處理,研究變質(zhì)后熔體攪拌工藝對變質(zhì)效果的影響規(guī)律,為充分發(fā)揮P的變質(zhì)作用提供理論依據(jù)。本實驗研究結(jié)果表明,對于Al-20%Si合金而言,在高于Cu-9%P合金熔化溫度以上攪拌時,攪拌越激烈,細化效果越好;隨著攪拌時間的延長,初生硅平均尺寸呈現(xiàn)出先減小后增大的變化規(guī)律。當(dāng)攪拌速度為224rad/min、攪拌時間為8min時,初生硅平均尺寸細化到17μm。對于Al-15%Si合金、Al-18%Si合金、Al-20%Si合金,在低于Cu-9%P合金熔化溫度以下攪拌時,隨著攪拌時間的延長,初生硅平均尺寸大體上呈現(xiàn)出先減小后增大的規(guī)律。攪拌越激烈,在最佳攪拌時間內(nèi)初生硅細化效果越好,攪拌時間過長,初生硅尺寸增加得越大。高轉(zhuǎn)數(shù)攪拌時(224rad/min),最佳攪拌時間與Si含量無關(guān),均在20min時細化效果最好;低轉(zhuǎn)數(shù)攪拌時(75rad/min),Si含量不同時最佳攪拌時間不同。對于Al-15%Si合金、Al-18%Si合金、Al-20%Si合金,當(dāng)攪拌速度為224rad/min、攪拌時間為20min時,初生硅平均尺寸分別細化到9μm、17μm、12μm,并且在Al-20%Si合金中典型的共晶組織消失,出現(xiàn)了顆粒狀的共晶硅。Si含量越高,初生硅平均尺寸降低的越多,細化效果越明顯。
[Abstract]:Hypereutectic Al-Si alloys have the advantages of low thermal expansion coefficient, good thermal stability, low density, high hardness, high temperature resistance and wear resistance. For hypereutectic Al-Si alloys, modification is usually used to refine primary silicon. Among the many modification methods, the effect of P modification on refining primary silicon is obvious, stable and easy to carry out. After adding P-containing master alloy into the melt of hypereutectic Al-Si alloy, it is necessary to stir the melt to obtain a better modification effect. However, it is not clear how the degree of stirring affects the modification effect. In this paper, Al-15%Si alloy, Al-18%Si alloy and Al-20%Si alloy are taken as research objects. The modification of Cu-9%P alloy is carried out, and the influence of melt stirring process on modification effect is studied, which provides a theoretical basis for giving full play to the modification of P. The experimental results show that, for Al-20%Si alloy, the more intense the stirring is, the better the refining effect is when the stirring temperature is higher than the melting temperature of Cu-9%P alloy, and with the prolongation of stirring time, The average size of primary silicon decreases first and then increases. When the stirring speed is 224rad / min and the stirring time is 8min, the average size of the primary silicon is refined to 17 渭 m. For Al-15%Si alloy, Al-18%Si alloy and Al-20%Si alloy, when the stirring temperature is below the melting temperature of Cu-9%P alloy, the average size of primary silicon decreases first and then increases with the prolonging of stirring time. The more intense the stirring, the better the refining effect of primary silicon is in the optimum stirring time, the longer the stirring time is, the larger the size of primary silicon is. The best stirring time was not related to the content of Si, but the thinning effect was best when 20min was used, and when the content of 75rad/min), Si was different, the optimum stirring time was different when the 75rad/min), Si content was different. For Al-15%Si alloy, Al-18%Si alloy and Al-20%Si alloy, the average size of primary silicon was refined to 9 渭 m ~ 17 渭 m ~ (12) 渭 m when stirring speed was 224rad / min and stirring time was 20min. The typical eutectic structure disappeared in Al-20%Si alloy, and the higher the content of Si was, the more granular eutectic silicon appeared. The more the average size of primary silicon decreases, the more obvious the refining effect is.
【學(xué)位授予單位】：遼寧工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG292
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本文編號：2270336