Please wait a minute...
金属学报  2016, Vol. 52 Issue (2): 191-201    DOI: 10.11900/0412.1961.2015.00334
  论文 本期目录 | 过刊浏览 |
汽车用新型Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金的制备及其时效析出行为研究*
李勇,郭明星(),姜宁,张许凯,张艳,庄林忠,张济山
北京科技大学新金属材料国家重点实验室, 北京 100083
PRECIPITATION BEHAVIORS AND PREPARATION OF AN ADVANCED Al-0.93Mg-0.78Si-0.20Cu-3.00Zn ALLOY FOR AUTOMOTIVE APPLICATION
Yong LI,Mingxing GUO(),Ning JIANG,Xukai ZHANG,Yan ZHANG,Linzhong ZHUANG,Jishan ZHANG
State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
全文: PDF(7441 KB)   HTML  
  
摘要: 

通过DSC, OM, SEM, TEM观察及拉伸测试等手段对新开发的汽车用新型Al-0.93Mg-0.78Si-0.20Cu-0.30Mn-0.40Fe-3.00Zn (质量分数, %)合金的时效析出行为进行了系统研究. 结果表明, 固溶淬火态合金的DSC曲线出现5个放热峰, 分别对应GP区聚集长大及沉淀相析出, 运用Avrami-Johnson-Mehl方法对合金时效析出动力学进行了计算分析, 创建的沉淀相析出动力学方程Y=1-exp[-2.03×1019exp(-23573/T)t2]可以比较准确地预测合金时效析出规律. 185 ℃人工时效90 min即可达到峰值硬度133 HV, 对应的拉伸性能可达σ0.2=346 MPa, σb=383 MPa, δ=13%, 拉伸断口仍以塑性断裂为主. 虽然该合金含有一定量的Zn, 但在185 ℃时效时仍以Mg-Si相的析出为主, 峰时效态分布有结构稳定的β′′相及其前驱体pre-β′′相, 后者的出现主要是由于Zn参与了沉淀相的析出所致. 此外, 根据合金时效过程的组织演化规律, 提出了该新型合金沉淀相形核和析出模型示意图.

关键词 Al-Mg-Si-Cu-Zn合金GP区β"相pre-β"相析出动力学    
Abstract

To reduce the weight of car body, Al-Mg-Si-Cu alloys have been widely used to produce outer body panels of automobiles due to their favorable high strength-to-weight ratio, corrosion resistance and good formability. However, their bake hardening responses still need to be further improved to enhance their dent resistance. In this work, an advanced Al-0.93Mg-0.78Si-0.20Cu-0.30Mn-0.40Fe-3.00Zn (mass fraction, %) alloy has been developed, its precipitation behavior has been investigated systematically through DSC, OM, SEM, TEM and tensile test. Five exothermic peaks were observed in DSC curve of the solution quenched alloy, these peaks were believed to be caused by the formation of GP zones and precipitate phases, the formation and dissolution of these precipitates were analyzed by Avrami-Johnson-Mehl method, a kinetic equation Y=1-exp[-2.03×1019exp(-23573/T)t2] has been established, which can be greatly used to predict the precipitation behavior. After artificial aging at 185 ℃for 90 min, the peak hardness of 133 HV can be obtained, corresponding to the predicted results. Additionally, the tensile properties in peak aging state, i.e. yield strength, ultimate tensile strength and elongation, are 346 MPa, 383 MPa and 13%, respectively, and ductile fracture is the main fracture feature as observed by SEM examination of fracture surface. Although 3.00%Zn is added in the alloy, yet, Mg-Si precipitates are still the main precipitates formed during artificial aging at 185 ℃. Both β′′ and pre-β′′ precipitates can be observed in the peak aging state, and the presence of the latter ones should be resulted from the formation of Zn-containing clusters. In addition, based on the microstructure evolution of the alloy, a schematic diagram of forming precipitates in the Al-Mg-Si-Cu-Zn alloy is put forwarded.

Key wordsAl-Mg-Si-Cu-Zn alloy    GP zone    β" phase    pre-β" phase    precipitation kinetics
收稿日期: 2015-06-26      出版日期: 2015-11-23
基金资助:* 国家高技术研究发展计划项目2013AA032403, 国家自然科学基金项目51571023和51301016, 中央高校基本科研业务费项目FRF-TP-15-051A3, 北京实验室建设项目FRF-SD-B-005B和新金属材料国家重点实验室开放课题项目2014-ZD05资助

引用本文:

李勇,郭明星,姜宁,张许凯,张艳,庄林忠,张济山. 汽车用新型Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金的制备及其时效析出行为研究*[J]. 金属学报, 2016, 52(2): 191-201.
Yong LI,Mingxing GUO,Ning JIANG,Xukai ZHANG,Yan ZHANG,Linzhong ZHUANG,Jishan ZHANG. PRECIPITATION BEHAVIORS AND PREPARATION OF AN ADVANCED Al-0.93Mg-0.78Si-0.20Cu-3.00Zn ALLOY FOR AUTOMOTIVE APPLICATION. Acta Metall, 2016, 52(2): 191-201.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2015.00334      或      http://www.ams.org.cn/CN/Y2016/V52/I2/191

图1  Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金不同状态的显微组织的OM像
图2  固溶淬火态Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金DSC曲线
图3  固溶淬火态合金DSC曲线GP区析出峰、溶解峰, 沉淀相析出峰及对应的激活能计算过程图
DSC peak Q / (kJmol-1) k0 / min-1 Kinetics expression
GP zone formation 30 2073.2 Y=1-exp[-4.30×106exp(-6374/T)t2]
GP zone dissolution 34 2202.6 Y=1-exp[-4.85×106exp(-8347/T)t2]
Precipitate formation 98 4.5×109 Y=1-exp[-2.03×1019exp(-23573/T)t2]
表1  GP区析出和溶解及沉淀相析出的动力学参数
图4  Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金185 ℃时效时沉淀相析出或溶解体积分数与时效时间的变化曲线
图5  固溶淬火态Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金在185 ℃时效时的硬度变化

2.2.3 典型状态拉伸性能 合金析出速率较快对于汽车用铝合金非常重要, 但是如果合金的强度不够理想仍然不适合广泛应用于汽车车身外板材料, 因此, 对合金进行了拉伸力学性能测量. 图6示出了Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金不同状态时的应力-应变曲线. 可以看出, 固溶淬火态合金屈服强度较低, 仅为70.8 MPa, 随着应变的增加, 应力-应变曲线表现出比较明显的波动现象. 这种现象在Al-Mg和Al-Zn-Mg-Cu合金中比较普遍, 即所谓的Portevin-LeChâtelier (PLC)塑性不稳定性效应[34,35], 此现象的出现会影响合金板材变形后的外表面质量. 导致PLC效应出现的原因主要是由于位错在运动过程中受到溶质原子拖拽所致, 也可能是由于应变诱发溶质原子团簇与空位结合并析出, 进而拉伸过程中运动位错不断被这些溶质原子团簇钉扎, 随后在切过这些团簇后应力必然会发生瞬间降低, 当遇到下一个溶质原子团簇时切应力又会升高, 所以可以观察到应力的波动现象. 此外, 从图6还可以看出, 即使经20 min的短时时效处理后, 合金屈服强度即可获得大幅度升高, 由固溶淬火态的70.8 MPa升高到312 MPa, 不过延伸率产生一定程度的降低. 随着时效时间的进一步延长, 达到90 min峰值时效状态时, 合金的屈服强度接近350 MPa, 而抗拉强度可达383 MPa, 虽然延伸率进一步下降, 不过仍然可达13%. 由此可见, Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金整体可以表现出较为优异的力学性能.

图6  Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金不同状态下的工程应力-应变曲线
图7  不同状态合金拉伸断口形貌的SEM像和固溶淬火态合金的EDS分析
图8  Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金固溶淬火态和经过185 ℃, 20 min和90 min人工时效后的TEM和HRTEM像及对应的Fourier变换像和模拟图
图9  Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金内沉淀相形成模型示意图

此外, 值得注意的是, 虽然Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金含有3.0%Zn, 但是在185 ℃时效过程中并未观察到Al-Zn-Mg合金中常见的Mg-Zn相, 如η′η相等. 这一方面可能是由于表征手段仍然有待进一步提高; 另一方面也可能是由于时效温度较高, 不利于Mg-Zn相的长大. 因为Al-Zn-Mg合金通常采用120 ℃时效会析出大量η′相, 但是温度较高时(如180 ℃以上), η′相不仅不会析出而且会发生回溶(如典型的T77回归热处理工艺).

[1] Miller W S, Zhuang L, Bottema J, Wittebrood A J, Smet P D, Haszler A, Vieregge A.Mater Sci Eng, 2000; A280: 37
[2] Murayama M, Hono K.Acta Mater, 1999; 47: 1537
[3] Dorward R C, Bouvier C.Mater Sci Eng, 1998; A254: 33
[4] Hirth S M, Marshall G J, Court S A, Lloyd D J.Mater Sci Eng, 2001; A319: 452
[5] Zhen L, Fei W D, Kang S B, Kim H W.J Mater Sci, 1997; 32: 1895
[6] Kim J H, Kobayashi E, Sato T.Mater Trans, 2011; 52: 906
[7] Man J, Jing L, Jie S G.J Alloys Compd, 2007; 437: 146
[8] Vaumousse D, Cerezo A, Warren P J, Court S A.Mater Sci Forum, 2004; 396: 693
[9] Luo Q Q.Melting and Casting of Aluminium Alloys. Guangzhou: Guangdong Science and Technology Press, 2002: 39
[9] (罗启全. 铝合金熔炼与铸造. 广州: 广东科技出版社, 2002: 39)
[10] Terziev L, Skenazi A, Greday T.Mater Sci Forum, 1987; 13: 369
[11] Bijlhouwer F. J Mater Sci Technol, 2009; 24: 157
[12] Engdahl T, Hansen V, Warren P J, Stiller K.Mater Sci Eng, 2002; A327: 59
[13] Saito T, Wenner S, Osmundsen E, Marioara C D, Andersen S J, Røyset J, Lefebvre W, Holmestad R.Philos Mag, 2014; 94: 2410
[14] Wang X F, Guo M X, Zhang Y, Xing H, Li Y, Luo J R, Zhang J S, Zhuang L Z.J Alloys Compd, 2016; 627: 906
[15] Wang X F, Guo M X, Chapuis A, Luo J R, Zhang J S, Zhuang L Z.Mater Sci Eng, 2015; A633: 46
[16] Wang X F, Guo M X, Cao L Y, Luo J R, Zhang J S, Zhuang L Z.Mater Sci Eng, 2015; A621: 8
[17] Peng X Y, Guo M X, Wang X F, Cui L, Zhang J S, Zhuang L Z.Acta Metall Sin, 2015; 51: 169
[17] (彭祥阳, 郭明星, 汪小锋, 崔莉, 张济山, 庄林忠. 金属学报, 2015; 51: 169)
[18] Wang X F, Guo M X, Chapuis A, Luo J R, Zhang J S, Zhuang L Z.Mater Sci Eng, 2015; A644: 137
[19] Cao L Y, Guo M X, Cui H, Cai Y H, Zhang Q X, Hu X Q, Zhang J S.Acta Metall Sin, 2013; 49: 428
[19] (曹零勇, 郭明星, 崔华, 蔡元华, 张巧霞, 胡晓倩, 张济山. 金属学报, 2013; 49: 428)
[20] Luo A, Lloyd D J, Gupta A, Youdelis W V.Acta Metall Mater, 1993; 41: 769
[21] Zhang Q X, Guo M X, Hu X Q, Cao L Y, Zhuang L Z, Zhang J S.Acta Metall Sin, 2013; 49: 1604
[21] (张巧霞, 郭明星, 胡晓倩, 曹零勇, 庄林忠, 张济山. 金属学报, 2013; 49: 1604)
[22] Edwards G A, Stiller K, Dunlop G L, Couper M J, Edwards G A, Stiller K.Acta Mater, 1998; 46: 3893
[23] De Geuser F, Lefebvre W, Blavette D.Phil Mag Lett, 2006; 86: 227
[24] Marioara C D, Andersen S J, Jansen J, Zandbergen H W.Acta Mater, 2001; 49: 321
[25] Gaber A, Ali A M, Matsuda K, Kawabata T, Yamazaki T, Ikeno S.J Alloys Compd, 2007; 432: 149
[26] Miao W F, Laughlin D E.Metall Mater Trans, 2000; 31A: 361
[27] Cuniberti A, Tolley A, Riglos M V C, Giovachini R.Mater Sci Eng, 2010; A527: 5307
[28] Esmaeili S, Lloyd D J, Poole W J.Acta Mater, 2003; 51: 3467
[29] Marceau R K W, De Vaucorbeil A, Sha G, Ringerc S P, Pooleb W J.Acta Mater, 2013; 61: 7285
[30] Esmaeili S, Lloyd D J.Acta Mater, 2005; 53: 5257
[31] Kim J H, Marioara C D, Holmestad R, Kobayashi E, Sato T.Mater Sci Eng, 2013; A560: 154
[32] Cui L, Guo M X, Peng X Y, Zhang Y, Zhang J S, Zhuang L Z.Acta Metall Sin, 2015; 51: 289
[32] (崔莉, 郭明星, 彭祥阳, 张艳, 张济山, 庄林忠. 金属学报, 2015; 51: 289)
[33] Li X L, Chen J H, Lui C H, Feng J N, Wang S H.Acta Metall Sin, 2013; 49: 243
[33] (李祥亮, 陈江华, 刘春辉, 冯佳妮, 王时豪. 金属学报, 2013; 49: 243)
[34] Krishna K, Sekhar K C, Tejas R, Krishnaa N N, Sivaprasada K, Narayanasamyb R, Venkateswarluc K.Mater Des, 2015; 67: 107
[35] Chen J Z, Zhen L, Fan L W, Yang S J, Dai S L, Shao W Z.Trans Nonferrous Met Soc China, 2009; 19: 1071
[36] Wolverton C.Acta Mater, 2001; 49: 3129
[37] Yang W C, Huang L P, Zhang R R, Wang M P, Li Z, Jia Y L, Lei R S, Sheng X F. J Alloys Compd, 2012; 514: 220
[1] 陈瑞,许庆彦,柳百成. Al-Mg-Si合金中针棒状析出相时效析出动力学及强化模拟研究*[J]. 金属学报, 2016, 52(8): 987-999.
[2] 王小娜, 韩利战, 顾剑锋. NZ30K镁合金时效析出动力学与强化模型的研究*[J]. 金属学报, 2014, 50(3): 355-360.
[3] 王晓亮 李长荣 郭翠萍 杜振民 何维. Mg-Zn合金时效过程中GP区析出的热力学分析[J]. 金属学报, 2010, 46(5): 575-580.
[4] 刘文昌;陈宗霖;肖福仁;姚枚;王少刚;刘润广. 冷轧变形对Inconel 718合金δ相析出动力学的影响[J]. 金属学报, 1998, 34(10): 1049-1054.
[5] 徐温崇;孙福玉;赵佩祥. 钢中(Nb,V)碳氮化物应变诱导析出动力学[J]. 金属学报, 1988, 24(5): 331-335.