7B50铝合金淬透性及其临界平均冷却速率研究
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摘要
本研究通过7B50合金改进型Jominy样品表面喷水淬火实验,在获得实测冷却曲线、不同时效状态合金的电导率和硬度的基础上,结合自然时效状态合金的微观组织,对7B50合金的淬透性及其临界平均冷却速率展开研究。结果表明:7B50合金自然时效50 d的淬透深度为70 mm,对应淬火敏感温度区间(420～230℃)内的平均冷却速率为1.55℃×s~(-1);先自然时效50 d再人工峰时效合金的淬透深度减至60 mm,对应的平均冷却速率为1.95℃×s~(-1);与自然时效状态相比,先自然时效再人工峰时效处理后合金的淬透性变差,淬火敏感性增加。表面喷水淬火时,非均匀析出相首先在晶界/亚晶界上析出,然后在基体内的Al_3Zr粒子上析出;晶界/亚晶界上观察到析出相,出现在距淬火表面仅3mm处,对应淬火敏感温度区间内的平均冷却速率高达981℃×s~(-1);基体内零星析出尺寸较小的非均匀析出相,出现在距淬火表面10mm处,对应的平均冷却速率为37.75℃×s~(-1)。喷水淬火后,距淬火表面25 mm处的性能与淬火表面处相比变化不大,该位置对应的平均冷却速率为9.34℃×s~(-1),远小于淬火表面处,控制7B50合金厚板的喷水淬火过程,使厚板内部的平均冷却速率接近但不低于9.34℃×s~(-1),厚板淬火-时效后将获得较好的性能。
The hardenability and critical cooling rates of 7B50 alloy were investigated based on measured cooling curves obtained from the sprayquenching test on modified Jominy specimen, electrical conductivity and hardness in different aging tempers, and microstructures evolution innatural aging temper. Results show that the hardened depth of 7B50 alloy is about 70 mm in natural aging temper while it decreases to 60 mm afternatural aging for 50 d followed by artificial peak aging treatment with the corresponding average cooling rates in quench sensitive temperaturerange(420～230 ℃) increasing from 1.55 ℃×s~(-1) to 1.95 ℃×s~(-1), indicating worse hardenability and more quench sensitivity after artificial peakaging treatment. During water-spray quenching, the precipitates form firstly on grain/subgrain boundaries and then at some special positions inmatrix, such as Al_3Zr particles. The inhomogeneous precipitates on grain/subgrain boundaries are observed at a location of 3 mm from thequenching surface with the corresponding average cooling rate of 981 ℃×s~(-1). While inhomogeneous precipitates in matrix are observed at alocation of 10 mm from the quenching surface with the corresponding average cooling rate of 37.75 ℃×s~(-1). Properties of the alloy at 25 mm fromthe quenching surface have little changed compared with those on the quenching surface and the corresponding average cooling rate at the locationof 25 mm is 9.34 ℃×s~(-1) which is much smaller than that on the quenching surface. Therefore, during the spray quenching process, the averagecooling rate of 7B50 alloy thick plates should be controlled to be close to but not less than 9.34 ℃×s~(-1), in order to get excellent and uniformproperties after quenching and aging.
The hardenability and critical cooling rates of 7B50 alloy were investigated based on measured cooling curves obtained from the sprayquenching test on modified Jominy specimen, electrical conductivity and hardness in different aging tempers, and microstructures evolution innatural aging temper. Results show that the hardened depth of 7B50 alloy is about 70 mm in natural aging temper while it decreases to 60 mm afternatural aging for 50 d followed by artificial peak aging treatment with the corresponding average cooling rates in quench sensitive temperaturerange(420～230 ℃) increasing from 1.55 ℃×s~(-1) to 1.95 ℃×s~(-1), indicating worse hardenability and more quench sensitivity after artificial peakaging treatment. During water-spray quenching, the precipitates form firstly on grain/subgrain boundaries and then at some special positions inmatrix, such as Al_3Zr particles. The inhomogeneous precipitates on grain/subgrain boundaries are observed at a location of 3 mm from thequenching surface with the corresponding average cooling rate of 981 ℃×s~(-1). While inhomogeneous precipitates in matrix are observed at alocation of 10 mm from the quenching surface with the corresponding average cooling rate of 37.75 ℃×s~(-1). Properties of the alloy at 25 mm fromthe quenching surface have little changed compared with those on the quenching surface and the corresponding average cooling rate at the locationof 25 mm is 9.34 ℃×s~(-1) which is much smaller than that on the quenching surface. Therefore, during the spray quenching process, the averagecooling rate of 7B50 alloy thick plates should be controlled to be close to but not less than 9.34 ℃×s~(-1), in order to get excellent and uniformproperties after quenching and aging.
引文
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[2]Zhang J,Deng Y L,Yang W et al.Materials and Design[J],2014,56(4):334
[3]Robinson J S,Cudd R L,Tanner D A et al.Journal of Materials Processing Technology[J],2001,119(1-3):261
[4]Conserva M,Fiorini P.Metallurgical Transactions[J],1973,4(3):857
[5]Xiong Baiqing(熊柏青),Li Xiwu(李锡武),Zhang Yong’an(张永安)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2011,21(10):2631
[6]Zhang Xinming(张新明),Zhang Duanzheng(张端正),Liu Shengdan(刘胜胆)et al.Journal of Central South University,Science and Technology(中南大学学报,自然科学版)[J],2015,46(2):421
[7]Li Peiyue(李培跃),Xiong Baiqing(熊柏青),Zhang Yong’an(张永安)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2011,21(5):961
[8]Liu Shengdan(刘胜胆),Li Chengbo(李承波),Li Lulu(李璐璐)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2012,22(6):1564
[9]Xu Xiaojing(许晓静),Zhang Yunkang(张允康),Deng Ping’an(邓平安)et al.Transactions of Materials and Heat Treatment(材料热处理学报)[J],2014,35(3):58
[10]Deng Y L,Wan L,Zhang Y Y et al.Journal of Alloys and Compounds[J],2011,509(13):4636
[11]Qi Xiaohong(祁小红),Deng Yunlai(邓运来),Liu Shengdan(刘胜胆)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2013,23(3):666
[12]Zhang Xinming(张新明),Yu Cuijuan(余翠娟),Liu Shengdan(刘胜胆)et al.Journal of Materials Engineering(材料工程)[J],2013(10):41
[13]Zheng Y L,Li C B,Liu S D et al.Transactions of Nonferrous Metals Society of China[J],2014,24(7):2275
[14]Zhang Xinming(张新明),Liu Wenjun(刘文军),Liu Shengdan(刘胜胆)et al.Transactions of Materials and Heat Treatment(材料热处理学报)[J],2010,31(6):33
[15]Zhang Xinming(张新明),Liu Shengdan(刘胜胆),You Jianghai(游江海)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2007,17(2):260
[16]Dai Xiaoyuan(戴晓元),Li Ni(李妮),Xiong Liang(熊亮).Materials Review(材料导报)[J],2015,29(3):75
[17]Newkirk J W,Mackenzie D S.Journal of Materials Engineering and Performance[J],2000,9(4):408
[18]Kang L,Zhao G,Tian N et al.Advanced Materials Research[J],2015,1095:168
[19]Kang Lei(康雷),Zhao Gang(赵刚),Tian Ni(田妮)et al.Light Alloy Fabrication Technology(轻合金加工技术)[J],2013,41(10):45
[20]Zhang Xinming(张新明),Liu Wenjun(刘文军),Liu Shengdan(刘胜胆)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2009,19(5):861
[21]Li Peiyue(李培跃),Xiong Baiqing(熊柏青),Zhang Yong’an(张永安)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2011,21(3):513
[22]Wang Guojun(王国军),Xiong Baiqing(熊柏青),Zhang Yong’an(张永安)et al.Chinese Journal of Rare Metals(稀有金属)[J],2009,33(3):304
[23]Sha G,Cerezo A.Acta Materialia[J],2004,52(15):4503
[24]Srivatsan T,Sriram S,Veeraraghavan D et al.Journal of Materials Science[J],1997,32(11):2883
[25]Berg L K,Gj?nnes J,Hansen V et al.Acta Materialia[J],2001,49(17):3443
[26]Deschamps A,Brechet Y.Scripta Materialia[J],1998,39(11):1517
[27]Buha J,Lumley R N,Crosky A G.Materials Science and Engineering A[J],2008,492(1-2):1
[28]Li P Y,Xiong B Q,Zhang Y A et al.Transactions of Nonferrous Metals Society of China[J],2012,22(2):268
[29]Liu Shengdan(刘胜胆),Li Chengbo(李承波),Deng Yunlai(邓运来)et al.Acta Metallurgica Sinica(金属学报)[J],2012,48(3):343
[30]Viana F,Pinto A M P,Santos H M C et al.Journal of Materials Processing Technology[J],1999,92-93:54
[31]Loffler H,Kovacs I,Lendvai J.Journal of Materials Science[J],1983,18(8):2215
[32]Dlubek G,Krause R,Brümmer O et al.Journal of Materials Science[J],1986,21(3):853