热处理对双辊铸轧ZK60镁合金组织及阻尼性能的影响

采用双辊铸轧法制备了ZK60镁合金条带,采用金相显微镜(OM)和动态机械分析仪(DMA)研究了热处理后ZK60镁合金条带的组织和阻尼性能。退火处理后,组织较为均匀。T6处理后组织转变为均匀的等轴晶。在温度-阻尼谱中出现了2个温度阻尼峰,P1峰为弛豫型阻尼峰,其激活能为132 kJ/mol,P2峰为非弛豫型再结晶阻尼峰。T6处理条件下,时效时间为6 h时,呈现典型的位错型应变-阻尼图谱;在其他时效时间下,呈现2种混合位错型的应变-阻尼图谱。T6态双辊铸轧ZK60镁合金的应变-阻尼性能遵循G-L理论。     

轧制路径对ZK60镁合金板材组织和性能的影响

在250 ℃对轧制-热处理态ZK60镁合金板材进行9道次不同路径的轧制试验。采用光学显微镜、电子万能试验机、SEM、XRD等研究了轧制试验后ZK60镁合金的显微组织、室温拉伸性能、断口形貌及晶粒择优取向。结果表明:轧制路径对ZK60镁合金板材的晶粒尺寸变化无明显影响,但压下量对镁合金组织内的孪晶变化有很大影响;轧制路径的变化对ZK60镁合金板材的各向异性和力学性能有较大影响,在交叉+45°的路径下轧制后ZK60镁合金板材,各向异性较弱,具有良好的综合力学性能和轧制成形能力,其屈服强度、抗拉强度和伸长率分别达到244.31 MPa、371.14 MPa和25.46%;交叉+45°路径轧制对ZK60镁合金的晶粒择优取向有明显影响,能够改善镁合金板材的晶粒择优取向和各向异性,提高ZK60镁合金的力学性能。     

Effect of magnetostatic field on microstructure of magnesium alloy ZK60

1　INTRODUCTIONNonferrousmaterialshavedisplayedmoreandmoreimportantrolesinthe 2 0 st century .Amongthesenonferrousmaterials ,magnesiumalloyisoneofthelightest practicalmaterial,butmagnesiumisametalwithastrongelectronegativity .Itsstandardelectricpotentialis - 2 .36 3V ,anditserosionresis tanceisnotgood .Becauseoftheoxidizationduringrefining ,deformationandapplication ,theadvantagesofmagnesiumalloysandtheirapplicationislimited .Asthedevelopmentoftherefiningtechnologyandad vancedformationte…     

ZK60镁合金热压变形和退火中的组织与织构演变

利用光学显微镜(OM)和扫描电镜悬挂的EBSD背散射衍射实验观察并研究了ZK60镁合金铸轧条带在热压(350℃/0.1 s-1)及退火处理(退火温度分别为250,300,350和400℃,退火时间分别为100,1000,5000,10000和50000 s)条件下的微观结构组织与织构演变。利用动态再结晶理论分析了ZK60镁合金铸轧条带、条带经小应变变形和大应变变形条件下的微观结构演变机理,利用静态再结晶理论分析了试样在不同热处理条件下的组织变化。结果表明,铸扎条带在热压变形后基面织构由弱变强,滑移和孪生导致动态再结晶发生,随应变增加,出现剪切带,晶粒明显细化。退火后基面织构逐渐弱化,基面沿轧制方向发生倾转,材料发生了明显静态再结晶。     

Effect of predeformation on semi-solid microstructure of ZK60＋RE magnesium alloy

Microscopical techniques were used to provide the semi-solid microstructure evolutions of ZK60+RE alloys formed by compression and equal channel angular extrusion(ECAE), respectively. It is found that after compression and ECAE, as-cast microstructures exhibit an obvious directional characteristic. The predeformation exerts a significant influence on the formation of thixotropic microstructures during partial remelting. Coalescence and Ostwald ripening are operative in the semi-solid mixture for both compression and ECAE formed alloys. Furthermore, the degree of spheroidization of ECAE formed alloy is better than that of compression formed alloy in appearance.     

ZK60镁合金异步降温轧制显微组织与力学性能的演变（英文）

将异步降温轧制应用于制造沿轧制方向具有弱基面织构的细晶ZK60镁合金板。结果表明,多道次降温轧制可以显著改善显微结构的均匀性,细化晶粒尺寸。同时,在轧制过程中逐渐形成沿横向的纤维织构。重要的是,沿轧向的剪切变形使基面的c轴向轧向旋转,削弱沿此方向的基面织构。受这种显微结构变化的影响,由于连续的晶粒细化和柱面滑移的增加,沿横向的屈服强度持续增加,而由于应变硬化能力的下降,均匀伸长率下降。相反,沿轧向的基面织构的持续减弱大大抵消晶粒细化所带来的强化效果,从而导致屈服强度的轻微下降。     

Effects of heat-treatment on microstructure of wrought magnesium alloy ZK60

The microstructure of the as-cast, as-solution-treated and as-aged wrought magnesium alloy ZK60 was studied. The results indicate that the microstructure of the as-cast ZK60 alloy is mainly composed of network eutectic （a-Mg＋MgZn） and divorced euteetic MgZn, which semi-continuously distribute along the grain boundaries or in the interdendritic area and almost dissolve into the matrix after solid solution treatment. The Laves phase MgZn2 is not sensitive to the heat treatment and seems to form at the early stage of solidification and keeps its size and shape till the aging stage. It is believed that the occurrence of the Laves phase in the ZK60 alloy would possibly contribute to the defects. Many new phases, including MgZn phase which is different from that forms during eutectic reaction, precipitate after aging treatment.     

Influence of aging on microstructure and properties of ZK60 magnesium alloy

The different aging process was investigated for ZK60 magnesium alloy to get the ideal synthetic properties. The results show that the values of strength, hardness and plasticity of ZK60 magnesium alloy increase at first and then decrease with increasing aging temperature, the suitable aging temperature of ZK60 alloy is from 160 to 180 ℃, At the meantime, the microstructures of appear mesh texture under high ageing temperature, this is the main reason why the mechanical properties decrease.     

热处理工艺对变形ZK60镁合金组织与性能的影响

采用拉伸试验、金相分析、SEM和TEM等方法测试和分析ZK60镁合金在挤压态、T5、T6及双级时效态下合金的力学性能和显微组织.结果表明,经过T5时效处理后,合金屈服强度和伸长率提高,而T6时效处理对合金的强度和伸长率影响不大,双级时效可明显提高合金的强度,但是伸长率稍有降低.经T5、T6时效后,合金中析出大量细小弥散的β'1相,为合金的主要强化相,双级时效能提高β'1相的析出密度,从而提高合金的强度.ZK60挤压态和T5态合金的断裂方式为混合型断裂,而T6和双级时效的断裂方式为解理断裂.     

Gd对ZK60镁合金组织与力学性能的影响

分析了铸态和挤压态ZK60?xGd(x=0~4)合金的组织和相组成,测试了其拉伸力学性能。结果表明,随着Gd含量的增加,铸态组织逐渐细化,Mg?Zn?Gd新相逐渐增多,而MgZn2相逐渐减少直至消失,第二相趋于连续网状分布于晶界处;当 Gd 含量不超过2.98%时,铸态室温拉伸力学性能稍降低。经挤压比λ=40和挤压温度T=593 K的挤压后,组织显著细化,平均晶粒尺寸逐渐减至ZK60?2.98Gd合金的2μm,破碎的第二相沿着挤压方向呈带状分布;挤压态的拉伸力学性能均显著提高：298和473 K时的抗拉强度分别从ZK60合金的355和120 MPa逐渐提高至ZK60?2.98Gd合金的380和164 MPa。挤压态拉伸断口呈现典型的韧性断裂特征。     

Influence of impurities on microstructure and mechanical properties of ZK60 magnesium alloy

The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy, scanning electron microscopy and tensile test. ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements. The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state. However, in the as-extruded state, reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa, while the elongations in the as-extruded alloys with different contents of impurities are almost the same. After T5 treatment, impurity content is found to have more obvious effect on the yield strength of ZK60 alloy. The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.     

轧制温度对AZ91镁合金组织及性能的影响

研究了不同变形温度对AZ91铸态镁合金轧制成形能力、微观组织及力学性能的影响,对热轧过程中第二相的分布及边裂行为进行了分析。结果表明,变形温度对AZ91铸态镁合金轧制成形性能影响显著。350℃和450℃轧制时,试样边部及表面出现明显横向裂纹,变形温度为400℃时,可获得较前两者更均匀细小的轧制组织,轧制成形性能明显提高。轧制试样的室温拉伸性能指标呈现先增加后减小的趋势,在400℃时达到最大值,抗拉强度和伸长率分别达到289 MPa和10.4%。     

Hot deformation behavior and processing map of squeeze cast ZK60 magnesium alloy

The deformation behavior of squeeze cast ZK60 magnesium alloy was investigated by compressive tests conducted at temperatures of 250-450 ℃ and strain rates of 0.001-10 s^-1 with Gleeble--1500D thermal simulator system. The hot deformation behavior of squeeze cast ZK60 magnesium alloy was characterized using processing map developed on the basis of the dynamic materials model. The processing map gives safe ＂processing windows＂ in which the processes of dynamic recovery and dynamic recrystallization occur. It reveals that the dynamic recrystallization domain occurs at 375 ℃ and strain rate of 0.001 s^-1, and its power dissipation efficiency approximately corresponds to 36%, which should be considered the optimum parameters for hot working of squeeze cast ZK60 magnesium alloy. The variation of the instability parameter ξ（ε） with temperature and strain rate constitutes an instability map, which is used for delineating the region of flow instability. The material exhibits flow instability which should be avoided in mechanical processing.     

Effect of large deformation on microstructure of ZK60 alloy

Microstructure evolution of ZK60 magnesium alloy deformed at 023 hoy cyclic extrusion compression （CEC） large deformation method was investigated. ZK60 alloy was deformed in the range of accumulated true strain of 0.8-17. The microstructure of evolution was investigated by optical microscope （OM） and transmission electron microscopy （TEM）. The results show that microstructure is obviously refined, and homogenous equiaxed microstructure is achieved in the entire range of the examined deformations by subjected to CEC deformation. By increasing the accumulated strain to 17, the grain size decreases into sub-micron regime with about several hundred nanometers. The mechanism of grain refinement in ZK60 alloy by CEC can be attributed to continuous dynamic recovery and recrystallization.     

往复挤压对挤压态ZK60镁合金微观组织和力学性能的影响

在350℃下,对挤压态ZK60镁合金分别进行1、4、8道次的往复挤压变形(CEC)。利用金相显微镜(OM)、透射电镜(TEM)观察往复挤压前后ZK60镁合金的微观组织,利用X射线衍射仪(XRD)分析变形前后晶面取向变化,在万能拉伸试验机上测试变形前后镁合金的力学性能,并利用扫描电镜(SEM)观察拉伸断口形貌。往复挤压后的检测结果表明,挤压态ZK60镁合金晶粒显著细化,晶粒尺寸分布较均匀,随着挤压道次增多,晶粒尺寸逐渐减小;1道次变形后组织内产生了大量晶格缺陷,出现了大角度晶界,第二相粒子分布在晶粒内部和晶界上;各晶面衍射峰增强,拉伸断口内存在大量基体撕裂棱和明显的韧窝分布;ZK60镁合金的力学性能变化较大,随着挤压道次增多,伸长率大幅提高,抗拉强度小幅增大,而屈服强度降低。     

ZK60镁合金在热轧过程中的组织细化及性能改善(英文)

采用多道次降温热轧工艺对ZK60镁合金铸锭进行累积大塑性变形。此工艺方法可促进动态再结晶细化晶粒的程度,经6道次轧制后,晶粒尺寸由铸态时的278μm细化至终轧板时的7.2μm。拉伸试验结果表明终轧板材在板平面内具有很好的强度各向同性,其屈服强度约为202MPa,抗拉强度约为307MPa,这与电子背散射衍射测试结果所揭示的良好组织均匀性和板平面晶粒取向分布均匀性相一致。进一步的研究表明,终轧板材不需要做进一步的时效处理,因此,本工艺方法在优化组织性能的同时,可以简化工艺流程和提高生产效率。