冷却速率对Al-20%Si合金Si相形貌及性能的影响
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摘要
使用高精度测温仪、金相显微镜(OM)和扫描电镜(SEM)等手段,研究了冷却速率、过冷度和再辉温度对Al-20%Si合金Si相形貌和性能的影响。结果表明:Al-20%Si合金初生Si的平均尺寸(D)与冷却速率(v)呈幂函数关系D=260.6v-3/4,而与再辉温度(Tm)则呈线性关系D=0.25Tm-143.12;降低初生Si生长的再辉温度,是控制晶粒长大的关键;铜模的高蓄热系数能持续降低初生Si的形核温度和再辉温度,使初生Si细小;初生Si由小平面生长转变为非小平面生长的临界过冷度为70 K,与理论计算结果(74 K)基本一致;随着冷却速率的增大、过冷度的增加和再辉温度的降低,Al-20%Si合金的凝固组织显著细化,合金的抗拉强度由167 MPa提高到210 MPa,延伸率则由2.14%提高到3.89%。
The effect of cooling rate, undercooling degree and recalescence temperature on the morphology of the primary Si-phase and the mechanical property of Al-20%Si alloy were investigated by means of high-precision thermometer, optical microscope(OM) and scanning electron microscopy(SEM). The results showed that the average size(D) of the primary Si in Al-20%Si alloy is a power function of the cooling rate(v) as D=260.6 v-3/4, and linearly related to the recalescence temperature(Tm) as D=0.25 Tm-143.12; Reducing the recalescence temperature of the primary Si growth was the key to control the grain growth, the copper mold with high thermal storage coefficient may be favourable to the sustainable reduction of the nucleation temperature and recalescence temperature of the primary Si, so that the primary Si size was small; The critical supercooling degree of 70 K was needed for the transformation of the primary Si growth from facet-like to non-facet-like ones, which is consistent with the theoretical calculation(74 K). With the increase of cooling rate and the undercooling degree, while the decrease of recalescence temperature, the solidified microstructure of Al-20%Si alloy was refined remarkably, correspondingly, the tensile strength of the Al-20%Si alloy increased from 167 MPa to 210 MPa and the elongation increased from 2.14% to 3.89 % respectively.
The effect of cooling rate, undercooling degree and recalescence temperature on the morphology of the primary Si-phase and the mechanical property of Al-20%Si alloy were investigated by means of high-precision thermometer, optical microscope(OM) and scanning electron microscopy(SEM). The results showed that the average size(D) of the primary Si in Al-20%Si alloy is a power function of the cooling rate(v) as D=260.6 v-3/4, and linearly related to the recalescence temperature(Tm) as D=0.25 Tm-143.12; Reducing the recalescence temperature of the primary Si growth was the key to control the grain growth, the copper mold with high thermal storage coefficient may be favourable to the sustainable reduction of the nucleation temperature and recalescence temperature of the primary Si, so that the primary Si size was small; The critical supercooling degree of 70 K was needed for the transformation of the primary Si growth from facet-like to non-facet-like ones, which is consistent with the theoretical calculation(74 K). With the increase of cooling rate and the undercooling degree, while the decrease of recalescence temperature, the solidified microstructure of Al-20%Si alloy was refined remarkably, correspondingly, the tensile strength of the Al-20%Si alloy increased from 167 MPa to 210 MPa and the elongation increased from 2.14% to 3.89 % respectively.
引文
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[18]Jian Z, Yang X, Chang F, et al. Solid-liquid interface energy be-tween silicon crystal and silicon-aluminum melt[J]. Metallurgical&Materials Transactions A, 2010, 41(7):1826
[2]Heard D W, Donaldson I W, Bishop D P. Metallurgical assessment of a hypereutectic aluminum-silicon P/M alloy[J]. Journal of Ma-terials Processing Technology, 2009, 209(18):5902
[3]Wang A Q, Zhang L J, Xie J P. Effects of cerium and phosphorus on microstructures and properties of hypereutectic AI-21%Si al-loy[J]. Journal of Rare Earths, 2013, 31(5):522
[4]Zuo M, Zhao D, Teng X, et al. Effect of P and Sr complex modifi-cation on Si phase in hypereutectic Al-30Si alloys[J]. Materi-als&Design, 2013, 47(9):857
[5]Sha M, Wu S, Zhong G, et al. Variation of microstructure of RE-con-taining AlSi20Cu2Ni1RE0.6alloy with different cobalt contents[J].Journal of Alloys and Compounds, 2011, 509(2):252
[6]Yang Z R, Pang S P, Sun Y, et al. Effect of modification and alloy-ing on microstructure and wear properties of hypereutectic Al-20%Si alloys[J]. The Chinese Journal of Nonferrous Metals, 2013(05):1217(杨子润,庞绍平,孙瑜等.变质及合金化对过共晶Al-20%Si合金组织及磨损性能的影响[J].中国有色金属学报, 2013(5):1217)
[7]Dang B, Jian Z Y, Chang F E, et al. Effect of melt thermal treat-ment on the solidification behavior and structure of Al-25%Si al-loy[J]. Sleep Medicine, 2015, 14:e232-e233
[8]Samuel A M, Garza-Elizondo G H, Doty H W, et al. Role of modi-fication and melt thermal treatment processes on the microstruc-ture and tensile properties of Al-Si alloys[J]. Materials&Design,2015, 80:99
[9]Zhao Z S, Zhao A M. Microstructures and formation mechanism of spray deposited high silicon aluminum alloy[J]. The Chinese Journal of Nonferrous Metals, 2000, 10(6):815(甄子胜,赵爱民.喷射沉积高硅铝合金显微组织及形成机理[J].中国有色金属学报, 2000, 10(6):815)
[10]Cui C, Schulz A, Schimanski K, et al. Spray forming of hypereu-tectic Al-Si alloys[J]. Journal of Materials Processing Technology,2009, 209(11):5220
[11]Xie L C, Peng C Q, Wang R C, et al. Morphology and microstruc-ture of rapidly solidified hypereutectic Al-Si alloy powder[J]. The Chinese Journal of Nonferrous Metals, 2014, 24(1):130(解立川,彭超群,王日初等.快速凝固过共晶铝硅合金粉末的形貌与显微组织[J].中国有色金属学报, 2014, 24(1):130)
[12]Dedyaeva E V, Akopyan T K, Padalko A G, et al. High-pressure phase transitions and structure of Al-20 at%Si hypereutectic alloy[J]. Inorganic Materials, 2016, 52(10):1077
[13]Wang R Y, Lu W H, Hogan L M. Growth morphology of primary silicon in cast Al-Si alloys and the mechanism of concentric growth[J]. Journal of Crystal Growth, 1999, 207(1):43
[14]Cahn J W, Hillig W B, Sears G W. The molecular mechanism of solidification[J]. Acta Metallurgica, 1964, 14(12):1421
[15]Jian Z, Kuribayashi K, Jie W, et al. Solid-liquid interface energy of silicon[J]. Acta Materialia, 2006, 54(12):3227
[16]Lide D R. CRC Handbook of Chemistry and Physics[M]. CRC Press, Inc, 1989
[17]Jian Z, Kuribayashi K, Jie W. Critical undercoolings for the transi-tion from the lateral to continuous growth in undercooled silicon and germanium[J]. Acta Materialia, 2004, 52(11):3323
[18]Jian Z, Yang X, Chang F, et al. Solid-liquid interface energy be-tween silicon crystal and silicon-aluminum melt[J]. Metallurgical&Materials Transactions A, 2010, 41(7):1826