Mg-Al-Sn-Mn系镁合金显微组织与力学性能的研究

发布时间：2018-03-06 00:24

本文选题：Mg-Al-Sn-Mn镁合金　切入点：显微组织　出处：《重庆大学》2015年博士论文　论文类型：学位论文

【摘要】：镁合金作为最轻的商用金属结构材料,具有高的比强度、比刚度,优良的阻尼性能等优点。镁合金在航空航天、汽车、3C等领域逐渐受到人们的关注,成为最具发展潜力的结构材料之一。室温强度不高、塑性差等因素制约了镁合金的发展。Mg-Al-Sn三元系具有较低的层错能,正发展成为一种性能优良的新型镁合金。然而,目前国内外对Mg-Al-Sn的研究还不够系统和深入。在本工作中,根据Mg-Al-Sn热力学数据构建了三元相图并设计了Mg-x Al-y Sn-0.3Mn(x=1,3,6,9;y=1,3,5)合金。基于金相分析、扫描电镜、能谱、X射线衍射、电子背散射衍射、透射电子显微分析、拉伸试验等手段,研究了成分对铸态合金显微组织与力学性能的影响、成分以及加工工艺对挤压态合金显微组织与力学性能的影响,探讨了铸造合金的晶粒细化机制以及挤压态合金的再结晶机制与强化机制,研究了部分合金的热压缩流变行为,确定了其本构方程以及热加工参数。主要结果如下:①Mg-Al-Sn-Mn合金主要含α-Mg、Mg17Al12和Mg2Sn,以及少量的含锰化合物[Al8Mn5、Al8(Mn,Fe)5]。通过edge-to-edge模型计算表明Mg17Al12与Mg2Sn存在惯习面(220)Mg2Sn//(330)Mg17Al12(夹角1.11o)、001s Mg2Sn//22—1—zMg17Al12。在合金凝固过程中,α-Mg首先形核并长大;随着温度的降低,Mg2Sn经过共晶反应L→α-Mg+Mg2Sn形核并长大;随着温度的进一步降低,Mg17Al12在Mg2Sn的惯习面上通过共晶反应L→α-Mg+Mg17Al12+Mg2Sn形核并长大;待液相消耗完毕,凝固完成。最终,铸造合金的晶粒随Al含量的增加而显著细化;Sn也有一定的细化效果,但弱于Al。铸造合金的强度随合金化元素含量的增加而增加,Sn对合金的强化效果弱于Al。②在未完全再结晶的挤压态Mg-x Al-y Sn-0.3Mn(x=1、3,y=1、3、5)合金中,粗大的未再结晶区域含较强的(101_0)、(0001)织构,未再结晶晶粒的(0001)基面法线方向以及112—0滑移方向趋向垂直于挤压方向;合金沿挤压方向受拉应力时,未再结晶区域a基面滑移系具有较小的施密特因子。再结晶弱化(101_0)织构,使再结晶晶粒的(0001)基面以及112—0滑移方向趋向平行于挤压方向;合金沿挤压方向受拉应力时,再结晶晶粒a基面滑移系具有较大的施密特因子。增加合金化元素含量或提高挤压温度可促进再结晶,降低合金的拉伸屈服强度;反之可有效提高合金的拉伸屈服强度。Mg-x Al-y Sn-0.3Mn(x=y=1,3)合金综合性能较优异(屈服强度200 MPa、延伸率~20%)③在完全再结晶的挤压态Mg-x Al-y Sn-0.3Mn(x=6、9,y=1、3、5)合金中,第二相(Mg17Al12、Mg2Sn)在热挤压过程中动态析出,有效阻碍再结晶晶粒长大,使成分、挤压温度对再结晶晶粒尺寸的影响变小;固溶强化、第二相强化是合金主要的强化机制。增加合金化元素含量或提高挤压温度可有效提高合金的拉伸屈服强度;Mg-9Al-y Sn-0.3Mn(y=1,3,5)合金具有较高的屈服强度(280 MPa)。④在挤压态Mg-Al-Sn-Mn合金中,分别研究了Al8Mn5、Mg2Sn、Mg17Al12与Mg基体的位向关系。Mg2Sn沿基面析出,两者位向关系为:(0001)Mg//(03?3)Mg2Sn,[21?1?0]Mg//[1?22]Mg2Sn;Mg17Al12析出相同样沿基面析出,两者位向关系为:(0001)Mg//(22?2)Mg17Al12,[21?1?0]Mg//[122]Mg17Al12;Al8Mn5析出相与Mg基体的位向关系为:(2_1_10)Mg//(202_0) Al8Mn5, [2_42_3]Mg//[011_1]Al8Mn5。⑤通过热模拟实验研究了Mg-x Al-y Sn-0.3Mn(x=y=1,3)合金的热压缩行为;计算了这些合金的热变形参数,确定了这些合金的本构方程。
[Abstract]:Magnesium alloy is the lightest structural materials, has high specific strength, stiffness, damping properties of magnesium alloy automobile. Excellent in aerospace, 3C, and other fields gradually attention, become one of the most potential structural materials. The strength at room temperature is not high, poor plasticity etc. the factors restricting the development of magnesium alloy.Mg-Al-Sn three element with low stacking fault energy, is becoming a new magnesium alloy with excellent properties. However, the current domestic and foreign research on Mg-Al-Sn systems and in-depth enough. In this work, according to the Mg-Al-Sn thermal mechanical data and construct a three element phase diagram and design Mg-x Al-y Sn-0.3Mn (x=1,3,6,9; y=1,3,5) alloy. Based on metallographic analysis, scanning electron microscopy, energy spectrum, X ray diffraction, electron backscatter diffraction, transmission electron microscopy, tensile tests, the effects of composition on cast microstructure and stress state alloy Effect of mechanical properties, composition and processing technology on the microstructure and mechanical properties of extruded alloy, discusses the mechanism of grain refinement of cast alloy and extruded alloy recrystallization mechanism and strengthening mechanism, the rheological behavior of part alloy was studied to determine the hot compression, the constitutive equations and thermal processing parameters. The main results as follows: Mg-Al-Sn-Mn alloy mainly containing alpha -Mg, Mg17Al12 and Mg2Sn, and a small amount of manganese containing compounds [Al8Mn5, Al8 (Mn, Fe) 5]. calculated by edge-to-edge model showed that Mg17Al12 and Mg2Sn (220) Mg2Sn// habit plane (330) Mg17Al12, 001s Mg2Sn//22 (angle 1.11o) - 1 - zMg17Al12. in alloy solidification process first of all, alpha -Mg nucleation and growth; with the decrease of temperature, the Mg2Sn eutectic reaction after L, alpha -Mg+Mg2Sn nucleation and growth; with a further reduction of temperature, Mg17Al12 on the Mg2Sn surface through the eutectic habitus Grow up, reaction of L alpha -Mg+Mg17Al12+Mg2Sn nucleation and liquid phase; to be consumed, solidification is completed. Finally, the grain cast alloy with the increase of Al content and significant refinement; Sn also has the certain refinement effect, but weaker than Al. increased the strength of the casting alloy with alloying element content increased, the strengthening effect of Sn on the alloy is weaker than Al. in Al-y extruded Mg-x Sn-0.3Mn not fully recrystallization (x=1,3, y=1,3,5) alloys, thick non recrystallization region containing the strong (101_0), (0001) texture, no recrystallization grains (0001) and 112 in the surface normal direction perpendicular to the sliding direction trend - 0 the extrusion direction along the extrusion direction; alloy tensile stress, the Schmidt factor Nonrecrystallization region a basal slip system has smaller recrystallization. Weakening (101_0) texture, make recrystallization grains (0001) surface and 112 - 0 slip orientation parallel to the extrusion direction along the alloy; The extrusion direction tensile stress, recrystallization grain a basal slip system has greatly increased the Schmidt factor. Alloying element content or improving extrusion temperature can promote the recrystallization, reduce the alloy tensile yield strength; and can effectively improve the tensile yield strength of.Mg-x Al-y Sn-0.3Mn (x=y=1,3) with excellent properties (yield alloy the intensity of 200 MPa, ~20%) in the elongation of the extruded Mg-x Al-y Sn-0.3Mn fully recrystallized (x=6,9, y=1,3,5) alloys, the second phase (Mg17Al12, Mg2Sn) Dynamic Precipitation in hot extrusion process, effectively prevent the recrystallization, the composition, effect of extrusion temperature on recrystallization grain size becomes smaller; solid solution strengthening, second phase strengthening mechanism of the alloy. The main alloying element content increasing or improving extrusion temperature can effectively improve the tensile yield strength; Mg-9Al-y Sn-0.3Mn (y=1,3,5) alloy has High yield strength (280 MPa). The extruded Mg-Al-Sn-Mn alloy, Mg2Sn, Al8Mn5, Mg17Al12 and Mg respectively, the matrix orientation relationship of.Mg2Sn along the surface precipitation, the two orientation relationship: (0001) Mg// (03? 3) Mg2Sn, [21? 1? 0]Mg//[1? 22]Mg2Sn Mg17Al12 the same kind of precipitation; along the surface precipitation, the two orientation relationship: (0001) Mg// (22? 2) Mg17Al12, [21? 1? 0]Mg//[122]Mg17Al12; Al8Mn5 precipitates and Mg matrix orientation relationship: (2_1_10) Mg// (202_0) Al8Mn5, [2_42_3]Mg//[011_1]Al8Mn5. and Mg-x Al-y Sn-0.3Mn were studied by thermal simulation (x=y=1,3) compression behavior of the alloy heat the calculation of these alloys; hot deformation parameters, determine the constitutive equations of these alloys.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG146.22

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