含Zr、Sc的Al-Zn-Mg-Cu合金的低周疲劳行为
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摘要
利用透射电子显微镜和低周疲劳试验机研究了单级时效状态及回归再时效状态两种含Zr、Sc的Al-Zn-Mg-Cu合金的微观组织和低周疲劳性能。结果表明:单级时效基体析出相以η′相为主,晶界析出连续分布平衡相,并伴有晶间无析出带;回归再时效基体析出相略有长大,晶界析出相长大明显,无析出带变宽。低周疲劳加载条件下,合金在0.4%~0.7%外加总应变幅范围内表现出循环稳定性;在0.8%的应变幅下,呈现先软化后硬化。在0.4%~0.6%较低的外加总应变幅范围内,回归再时效合金表现出较高的低周疲劳寿命。两种状态合金的塑性应变幅和弹性应变幅与载荷反向周次之间均成直线关系,并可分别用Coffin-Manson公式和Basquin公式来描述。两种状态的合金的疲劳裂纹均萌生于试样表面,并以穿晶方式扩展。
The single stage aging and RRA treatment on both microstructure and fatigue properties of Al-Zn-Mg-Cu alloy with Zr and Sc content were investigated through the transmission electron microscope and the low-cycle fatigue tests.In the single aging treatment state,the major precipitates inside the grains areη′phases,the discontinuous equilibrium phase precipitates at the grain boundaries,and there exist the precipitate free zones near the grain boundaries.For the alloy subject to RRA treatment state,the precipitates both inside the grains and at the grain boundaries obviously grow,and the precipitate free zone widens.Under the low-cycle fatigue loading condition,the alloy with different heat treatment states exhibits mainly the stable cyclic stress response behavior at the total strain amplitudes ranged from 0.4%to 0.7%.However,at the total strain amplitude of 0.8%,the alloy shows mostly the cyclic strain softening followed by the cyclic strain hardening.At the total strain amplitudes from 0.4% to 0.6%,the RRA treatment can effectively prolong the low-cycle fatigue lives of the alloy.The relationships between the plastic strain amplitude,elastic strain amplitude and reversals to failure are linear,and can be described separately with the Coffin-Manson formula and Basquin equations.In addition,the fatigue cracks initiate transgranularly at the free surface of fatigue samples and propagate transgranularly.
The single stage aging and RRA treatment on both microstructure and fatigue properties of Al-Zn-Mg-Cu alloy with Zr and Sc content were investigated through the transmission electron microscope and the low-cycle fatigue tests.In the single aging treatment state,the major precipitates inside the grains areη′phases,the discontinuous equilibrium phase precipitates at the grain boundaries,and there exist the precipitate free zones near the grain boundaries.For the alloy subject to RRA treatment state,the precipitates both inside the grains and at the grain boundaries obviously grow,and the precipitate free zone widens.Under the low-cycle fatigue loading condition,the alloy with different heat treatment states exhibits mainly the stable cyclic stress response behavior at the total strain amplitudes ranged from 0.4%to 0.7%.However,at the total strain amplitude of 0.8%,the alloy shows mostly the cyclic strain softening followed by the cyclic strain hardening.At the total strain amplitudes from 0.4% to 0.6%,the RRA treatment can effectively prolong the low-cycle fatigue lives of the alloy.The relationships between the plastic strain amplitude,elastic strain amplitude and reversals to failure are linear,and can be described separately with the Coffin-Manson formula and Basquin equations.In addition,the fatigue cracks initiate transgranularly at the free surface of fatigue samples and propagate transgranularly.
引文
1 Dursun T,Soutis C.Recent developments in advanced aircraft aluminum alloys[J].Mater Des,2014,56:862.
2 Gonzalo B,Jorge R G,JoséM.Recent developments in advanced aircraft aluminum alloys[J].J Mater Eng Perform,2009,18:1144.
3 Senkov O N,Shagiev M R,Senkova S V,et al.Precipitation of Al3-(Sc,Zr)particles in an Al-Zn-Mg-Cu-Sc-Zr alloy during conventional solution heat treatment and its effect on tensile properties[J].Acta Mater,2008,56(15):3723.
4 Zhang W,Xing Y,Jia Z H,et al.Effect of minor Sc and Zr addition on the microstructure and properties of ultra-high strength alloy[J].Trans Nonferrous Metals Soc China,2014,24:3866.
5 Dezecot S,Brochu M.Microstructural characterization and high cycle fatigue behavior of invesment cast A357aluminum alloy[J].Int J Fatigue,2015,77:154.
6 Zupanc U,Grum J.Effect of pitting corrosion on fatigue performance of shot-peened aluminium alloy 7075-T651[J].J Mater Processing Technol,2010,210:1197.
7 Han S W,Katsumata K,Kumai S,et al.Effects of solidification structure and aging condition on cuclic stress-strain response in Al-7%Si-0.4%Mg cast alloys[J].Mater Sci Eng A,2002,337(1-2):170.
8 Michael D S,Hans J M,Huseyin S.Aphysically based fatigue model for predicition of crack iniation form persistent slip bands in polycrystals[J].Acta Mater,2011,59(1):328.
9 Miao J,Pollock T M,Jones J W.Microstructural extremes and the transition from fatigue crack initiation to small crack growth in a polycrystalline nickel-base superalloy[J].Acta Mater,2012,60(6-7):2840.
10 Kim S W,Han S W,Lee U J,et al.Effect of solidication structure on fatigue crack growth in rheocast and thixocast Al-Mg-Si alloys[J].Mater Lett,2004,58(1-2):257.
11 Coffin L F.A study of the effects of cyclic thermal stresses on aductile metal[J].Trans Am Soc Mech Eng,1954,76:931.
12 Adam N,Chalid E D,Heinz K,et al.New method for evaluation of the Manson-Coffin-Basquin and Ramberg-Osgood equations with respect to compatibility[J].Int J Fatigue,2008,30(10-11):1967.
13 Dai X Y,Xia C Q,Long C G,et al.Morphology of primary Al3-(Sc,Zr)of as-cast Al-Zn-Mg-Cu-Zr-Sc alloys[J].Rare Matal Mater Eng,2011,40(2):265(in Chinese).戴晓元,夏长清,龙春光,等.Al-Zn-Mg-Cu-Zr-Sc合金铸态Al3(Sc,Zr)相形貌的研究[J].稀有金属材料与工程,2011,40(2):265.
14 Wu X M,Wang Z G,Li G Y.Cyclic deformation and strain burst behavior of Cu-7at.%Al and Cu-16at.%single crystals with different orientations[J].Mater Sci Eng A,2001,314(1-2):39.
2 Gonzalo B,Jorge R G,JoséM.Recent developments in advanced aircraft aluminum alloys[J].J Mater Eng Perform,2009,18:1144.
3 Senkov O N,Shagiev M R,Senkova S V,et al.Precipitation of Al3-(Sc,Zr)particles in an Al-Zn-Mg-Cu-Sc-Zr alloy during conventional solution heat treatment and its effect on tensile properties[J].Acta Mater,2008,56(15):3723.
4 Zhang W,Xing Y,Jia Z H,et al.Effect of minor Sc and Zr addition on the microstructure and properties of ultra-high strength alloy[J].Trans Nonferrous Metals Soc China,2014,24:3866.
5 Dezecot S,Brochu M.Microstructural characterization and high cycle fatigue behavior of invesment cast A357aluminum alloy[J].Int J Fatigue,2015,77:154.
6 Zupanc U,Grum J.Effect of pitting corrosion on fatigue performance of shot-peened aluminium alloy 7075-T651[J].J Mater Processing Technol,2010,210:1197.
7 Han S W,Katsumata K,Kumai S,et al.Effects of solidification structure and aging condition on cuclic stress-strain response in Al-7%Si-0.4%Mg cast alloys[J].Mater Sci Eng A,2002,337(1-2):170.
8 Michael D S,Hans J M,Huseyin S.Aphysically based fatigue model for predicition of crack iniation form persistent slip bands in polycrystals[J].Acta Mater,2011,59(1):328.
9 Miao J,Pollock T M,Jones J W.Microstructural extremes and the transition from fatigue crack initiation to small crack growth in a polycrystalline nickel-base superalloy[J].Acta Mater,2012,60(6-7):2840.
10 Kim S W,Han S W,Lee U J,et al.Effect of solidication structure on fatigue crack growth in rheocast and thixocast Al-Mg-Si alloys[J].Mater Lett,2004,58(1-2):257.
11 Coffin L F.A study of the effects of cyclic thermal stresses on aductile metal[J].Trans Am Soc Mech Eng,1954,76:931.
12 Adam N,Chalid E D,Heinz K,et al.New method for evaluation of the Manson-Coffin-Basquin and Ramberg-Osgood equations with respect to compatibility[J].Int J Fatigue,2008,30(10-11):1967.
13 Dai X Y,Xia C Q,Long C G,et al.Morphology of primary Al3-(Sc,Zr)of as-cast Al-Zn-Mg-Cu-Zr-Sc alloys[J].Rare Matal Mater Eng,2011,40(2):265(in Chinese).戴晓元,夏长清,龙春光,等.Al-Zn-Mg-Cu-Zr-Sc合金铸态Al3(Sc,Zr)相形貌的研究[J].稀有金属材料与工程,2011,40(2):265.
14 Wu X M,Wang Z G,Li G Y.Cyclic deformation and strain burst behavior of Cu-7at.%Al and Cu-16at.%single crystals with different orientations[J].Mater Sci Eng A,2001,314(1-2):39.