Mg-Al4C3中间合金对AZ31B镁合金组织的细化

采用SEM、EDS 和XRD 等测试手段研究Mg-50%Al4C3中间合金对AZ31B 镁合金显微组织的细化效果.研究结果表明,中间合金的加入可显著细化AZ31B镁合金的枝晶组织和晶粒尺寸.当Al4C3的加入量为0.9%时,α-Mg 晶粒的平均尺寸由基体合金的280 μm降至约53 μm.β相由连续网状转变为不连续的网状和细小弥散的粒状.通过能谱分析及面错配度计算证实,Al4C3可成为初生α-Mg晶粒的良好异质核心.     

铸造镁合金的晶粒细化研究进展

介绍了铸造镁合金晶粒细化方面最近的研究进展,指出Al2RE颗粒是有效的形核剂,可用来细化镁-稀土合金和含Al镁合金。其在镁合金中的广泛应用还有待进一步研究。     

粗晶粒铸轧AZ31镁合金的高温拉伸性能

研究了具有较大晶粒尺寸铸轧态AZ31镁合金的高温拉伸性能。通过热处理获得晶粒尺寸d=27．8μm的板材,对不同试样,在温度分别为300,350,400,450℃恒温条件下,以10^-3s^-1和10^-3s^-1恒定拉伸速率对试样进行拉伸至失效实验。结果表明,粗晶粒AZ31镁合金在450℃和10^-3s^-1条件下达到最大的延伸率106．7％。拉伸试样断口形貌的分析表明,450℃时出现丝状物质是合金出现液态zn的结果。少量的液相可以释放应力集中和协调此时的变形过程。与细晶粒铸轧态AZ31相比,在拉伸条件相同和晶粒尺寸不同的情况下,粗晶粒的塑形较低,其原因是晶界滑移在变形时所作贡献少。     

AZ31镁合金板材复合形变的孪晶组织及晶粒尺寸

研究了复合形变对镁合金AZ31板材性能的影响规律,比较了不同变形齿间比、温度和压下量对镁合金板材微观组织的影响。研究结果表明,在复合变形条件下,随着齿间比的增大,板材孪晶体积分数逐渐减小,平均晶粒尺寸有先减小后增大的趋势。随着压下量的逐渐增大,板材的孪晶体积分数逐渐增大,平均晶粒尺寸也有先减小后增大的趋势。同时过大的压下量容易导致板材断裂。随着变形温度的提高,板材能完成较大的变形量,但是孪晶体积分数逐渐减少,晶粒尺寸先减小后增大。     

AZ31B变形镁合金板材的TIG焊接

采用TIG焊对5 mm厚AZ31B挤压镁合金板材进行了焊接试验。采用万能拉伸试验机、金相显微镜、扫描电子显微镜和显微硬度仪等分析测试手段对焊接接头的组织、力学性能以及断口形貌等进行了分析。探讨了焊接电流对焊接接头的组织及力学性能的影响,揭示了不同焊接电流下焊接接头的断裂机制。结果表明,采用TIG焊焊接5 mm厚AZ31B镁合金板时,开X型坡口,采用双面焊接双面成型工艺,在130~145 A焊接电流及合适焊接速度条件下,能得到表面成型良好的焊接接头。当正反面焊接电流均为145 A时,AZ31B镁合金板焊接接头的抗拉强度达到最大值248.6 MPa,约为母材强度的84.0%。AZ31B镁合金板焊缝区显微硬度比母材区稍有所下降,热影响区显微硬度下降比较严重。当焊接电流为145 A时,AZ31B镁合金板焊接拉伸断口有大量韧窝,属韧性断裂。     

基于元胞自动机AZ31镁合金固溶处理研究

镁合金具有导热导电性好、电磁屏蔽性能优越、与环境相容性良好等诸多优点。但是镁合金在室温下塑性较差,导致其在轧制过程中易出现裂纹从而影响其质量。为了有效提高其可塑性,在加工前往往需要对其进行固溶处理。基于此,通过金相实验,得到AZ31镁合金管材原始晶粒组织,基于晶粒长大的热力学机制、曲率驱动机制和能量耗散机制,建立元胞自动机模型,针对镁合金建立了三大晶粒演变规则,研究AZ31镁合金在不同温度和不同时间下晶粒演变规律与边数变化情况,最终获得晶粒均匀分布且以六边形为主的微观组织。通过晶粒长大拓扑学分析与晶粒尺寸分布统计,得出晶粒尺寸在不同温度和时间内呈正态分布,其中六边形晶粒最多;在此基础上,建立固溶情况下的晶粒长大数学模型,合理预测并控制AZ31镁合金固溶后的晶粒尺寸和最终性能,分析了晶粒长大动力学,得出镁合金生长指数为0.87,并通过实验验证了元胞自动机模型的正确性和合理性,为研究镁合金在变形过程中的晶粒演变奠定基础。     

Mg—Sr—Y中间合金对AZ31镁合金铸态组织的影响

采用光学金相显微镜、扫描电子显微镜、能谱仪、XRD等对Mg—Sr-Y中间合金、AZ31-0．5％Sr和AZ31-0．5％Sr－1．5％Y的组织、相结构进行研究。结果表明,Mg—Sr—Y中间合金的组织由基体α—Mg相、沿晶界分布的枝晶状的共晶组织（Mg17Sr2＋Mg11Y）组成,Sr、Y可以细化AZ31镁合金晶粒,其细...     

Mg—Sr—Y中间合金对AZ31镁合金铸态组织的影响

采用光学金相显微镜、扫描电子显微镜、能谱仪、XRD等对Mg—Sr-Y中间合金、AZ31-0．5％Sr和AZ31-0．5％Sr－1．5％Y的组织、相结构进行研究。结果表明,Mg—Sr—Y中间合金的组织由基体α—Mg相、沿晶界分布的枝晶状的共晶组织（Mg17Sr2＋Mg11Y）组成,Sr、Y可以细化AZ31镁合金晶粒,其细化效果与Sr、Y含量有关。     

ZM5型铸造镁合金的晶粒细化

以自行铸造的ZM5型镁合金为基,添加多种变质剂C,C2Cl6,FeCl3,TiO2等,以细化镁合金晶粒,并比较其细化效果.实验结果表明,以上变质剂均能显著细化晶粒,且细小等轴的晶粒组织可以改善其力学性能.其中,C2Cl6的细化效果最为明显.     

Improved mechanical properties in AZ31 magnesium alloys induced by impurity reduction

Mechanical properties and microstructures of AZ31 magnesium alloys containing different impurity levels but having the same alloying element content, were investigated at ambient temperature. These AZ31 alloys were produced by semi-continuous casting, wherein the content of impurity was varied systematically. Microstructure observation shows that finer grains are existent in the alloy with lower impurity level. Tensile testing reveals that a reduction of impurity content results in a noticeable increase of the strength and elongation in the alloys in the cast, homogenized and extruded states. As the impurity content decreases from 0.0462wt% to 0.0163wt%, the ultimate tensile strength is evidently enhanced by 62 MPa and the elongation is nearly doubled in the homogenized specimen. The observed property improvement was discussed in terms of the microstructure variation with impurity reduction.     

Superplastic Deformation Behavior of Hot-rolled AZ31 Magnesium Alloy Sheet at Elevated Temperatures

1IntroductionAs a typical wrought magnesiumalloy,AZ31alloyhas a wide prospect for applications inthe fields of auto-mobiles,electronic appliances and aeronautic facili-ties[1,2].However,due to the hexagonal close-packed(HCP)structure of magnesium,the ductility of AZ31al-loy at roomtemperature is rather poor,which greatly re-stricts its applications in structural fields[3-5].Owing tothe activation of non-basal slip system[6],the ductility ofMg alloycan be significantlyimproved at elevatedtem…     

Constitutive analysis of AZ31 magnesium alloy plate

The plastic deformation simulation of AZ31 magnesium alloy at different elevated temperatures (from 473 to 723 K) was performed on Gleeble-1500 thermal mechanical simulator at the strain rates of 0.01, 0.1, 1, 5 and 10 s-1 and the maximum deformation degree of 80%. The relationship between the flow stress and deformation temperature as well as strain rate was analyzed. The materials parameters and the apparent activation energy were calculated. The constitutive relationship was established with a Zener-Holl...     

大规格AZ31B变形镁合金坯料的高纯净化制备

为了实现高纯大规格AZ31B变形镁舍金坯料工业化生产,通过对原辅料的控制,采用双联气体保护熔炼、电磁泵转移和液压式半连续铸造,并严格控制熔炼温度、浇铸温度、浇铸水压和浇铸速度,生产出了质量较高的变形镁舍金坯料．经检测,化学成分符舍ASTM—B93标准,内部组织和纯净度符合Q／QC011—2006规定,     

Refinement role of electromagnetic stirring and calcium in AZ91 magnesium alloy

Effects of calcium addition and electromagnetic stirring on the microstructure of AZ91 magnesium alloy and refinement mechanism were investigated. The results show that calcium addition ranging from 0.1wt% to 0.3 wt% does not lead to formation of any new phases but cause the refinement of ascast microstructure.However, combined calcium alloying and electromagnetic stirring significantly decrease the grain size, change the morphologies of the β-Mg17Al12 phases,and reduce their volume percentage. The minimum grain size of AZ91 alloy is obtained in the case of the addition of 0.2 wt%Ca with exciting voltage of 100 V. The microstructural refinement is attributed to the increase of the degree of undercooling and nucleation temperature of primary α-Mg phases on the basis of DTA analysis results.     

间断变形工艺提高AZ31镁合金超塑性的研究

研究间断变形工艺对AZ31镁合金超塑性的影响。结果表明,当温度为400-440℃、应变速率小于5×10^-4s^-1时,间断变形工艺可以显著提高AZ31镁合金的超塑性。计算了空洞体积分数与空洞数量的关系。结果表明,空洞体积分数与空洞数量呈正比。对拉伸试样断口形貌的分析表明,间断变形减少了空洞数量,因而减小了空洞体积分数,提高了超塑性伸长率。     

As-extruded AZ31B magnesium alloy fatigue crack propagation behavior

The fatigue crack propagation rate of as-extruded AZ31B magnesium alloy was studied. Compact tension [C(T)] of the notch direction parallel (T-L), vertical (L-T), and inclined at 45o to the extrusion direction was investigated. The experimental results indicate that the crack propagation direction is parallel to the extrusion direction for T-L and L-T specimens, whereas the specimen inclined at 45o has an angular deflection of 9° to 11° toward the extrusion direction. The T-L specimen has the fastest fatigue crack propagation rate, and the L-T specimen has the slowest rate, the fatigue crack propagation rate of the specimen inclined at 45o is between the two directions. The crack tip propagates by both transgranular and intergranular fractures. Fatigue fractures consist of cleavage plane or quasi-cleavage and are brittle fractures. The fatigue striation occurs for specimens inclined at 45o and its size is 3-15 μm.     

Microstructure evolution of AZ31 Mg alloy during change channel angular extrusion

Microstructure evolution of AZ31 Mg alloy during change-channel angular extrusion (CCAE) was investigated. The grains of AZ31 Mg alloy were refined significantly from 500 mm to 15 mm after CCAE deformed at 523 K. Dislocations were induced at the initial stage of extrusion and they rearranged themselves to form dislocation boundaries and sub-grain boundaries during deformation. When the specimen through the horizontal change channel with the strain increased, the sub-boundaries evolved to high angle grain boundaries (HAGB). The process of grain refinement can be described as continuous dynamic recovery and recrystallization (CDRR).