热处理对ZM51镁合金力学性能的影响

通过光学显微镜(OM)、硬度测试以及室温拉伸等分析手段研究了挤压态Mg-5%Zn-1%Mn(质量分数)合金固溶处理、单级时效处理、固溶+单级时效处理、双级时效处理以及固溶+双级时效处理制度,以及分析了不同热处理制度对ZM51镁合金组织及力学性能的影响。结果表明:工业化挤压生产大截面尺寸的ZM51镁合金经不同时效制度处理后,强度均不同程度的提高,且时效制度不同,合金强度提高的大小也不尽相同。经T6处理的合金峰时效强度大于T5处理的合金峰时效强度,双级时效处理的合金峰时效强度大于单级时效处理的合金峰时效强度,同时, T6处理和双级时效处理的合金断后伸长率均低于T5处理以及单级时效处理的合金断后伸长率。经T6双级时效处理的合金强度最高,断后伸长率最低,抗拉强度达到了340.52 MPa,断后伸长率为6%。此外,大截面尺寸ZM51镁合金挤压材可通过调整工艺,直接借助现有铝合金大型生产设备实现工业化生产。     

T5热处理对挤压态ZK60镁合金组织性能的影响

对均匀化、挤压、挤压 T5三种状态的ZK60镁合金的组织及拉伸性能进行了研究.结果表明,铸态ZK60合金经450℃×14 h均匀化处理后,其组织基本为单相固溶体,塑性大大提高,伸长率提高近一倍;以不同挤压比挤压后,其晶粒均得到细化,力学性能得到不同程度的提高,在挤压比为30时,合金的综合性能最优;挤压材经T5处理后,晶粒度变化不大,但析出相明显增多并部分聚集长大,导致其强度、硬度提高,而伸长率却略有降低.     

热处理及热挤压对Mg-10Gd-4.8Y-0.6Zr组织及常温力学性能的影响

通过力学和显微硬度测试、能谱和X射线衍射分析以及光学显微镜、扫描电镜和透射电镜观察,对Mg-10Gd-4.8Y-0.6Zr合金经均匀化、挤压变形及时效处理后的显微组织和常温力学性能进行研究。结果表明,铸态合金经520℃/16 h均匀化处理后网状共晶消除,并有黑色方块相生成,强度和塑性显著提高;挤压变形后的合金,抗拉强度σb达304.5 MPa,比挤压前提高25%,屈服强度σ0.2成倍增加,达268.7 MPa;在200℃时效20 h后峰值硬度达到137 HV;再经挤压和峰值时效后最终σb为370 MPa,比挤压态合金试样提高22%,屈服强度σ0.2为295.6 MPa,提高10%,但伸长率δ略有下降;该合金在室温下的断裂方式是脆性和韧性断裂兼有的混合断裂。     

热处理对挤压态AZ61-x%La镁合金组织和性能的影响

采用光学显微镜、扫描电镜(SEM)、X射线衍射(XRD)及拉伸实验等方法研究了热处理对挤压态AZ61-x%La镁合金显微组织和力学性能的影响。结果表明,经过T6处理后,原来弥散分布于晶界周围的β-Mg17Al12相经历了从完全溶解到重新析出的过程,并重新分布于晶界周围;β-Mg17Al12相由铸态的网状结构变成块状结构。在晶内一部分区域也出现了小块状的β相。合金中的稀土相能细化晶粒,显著提高合金的硬度。经过T6处理之后合金的抗拉强度,屈服强度和伸长率都有提高,但硬度略有下降。T5处理对合金的力学性能影响不大。     

单晶高温合金DD6不同状态下的显微组织和力学性能

研究了低成本的第二代单晶高温合金DD6在铸态、固溶处理状态和完全热处理状态的显微组织、拉伸性能和持久性能.结果表明在铸态、固溶处理和完全热处理三种状态中,完全热处理状态下DD6合金拉伸强度和持久寿命最高,分别为铸态的1.1倍和2.5～3倍;采用适当的热处理工艺可提高DD6合金中γ'相的数量,改善γ'相的尺寸和分布,显著提高合金的综合力学性能.     

挤压过程中剪切间隙对EW 75合金组织及力学性能的影响

通过OM、SEM和拉伸试验研究了剪切间隙对EW 75稀土镁合金挤压排材微观组织和力学性能的影响。试验结果表明:铸态合金的显微组织为:α-Mg基体,共晶组织。晶粒尺寸大约是80μm。挤压态合金呈现出比铸态更好的力学性能,抗拉强度331 MPa,屈服强度258 MPa,伸长率为10.8%,没有在分界线附近断裂,说明剪切间隙对挤压排材影响较小。     

含银A1-4.5Zn-1.0Mg-0.5Cu合金的强化固溶行为

采用拉伸力学性能测试、金相显微观察、扫描电镜及透射电镜等分析手段,研究了Al-4.5Zn-1.0Mg-0.5Cu-0.4Ag合金的强化固溶行为.结果表明:经强化固溶处理后,合金固溶态的抗拉强度和屈服强度以及伸长率分别较常规固溶的低15 MPa、16 MPa和1.7％;峰值时效态的抗拉强度和屈服强度较常规固溶的分别高62...     

Mg-Y-Nd-Zr合金加工工艺与组织演化的研究

对Mg-Y-Nd-Zr镁合金铸锭分别进行挤压和锻压变形加工，然后对变形加工件进行固溶、时效处理。采用金相显微镜、扫描电镜及能谱仪分析研究了该合金的组织演化过程。分别测试了铸造、挤压、锻压和热处理等不同状态下合金试样的室温和250℃力学性能。结果表明，该合金在350-400℃内进行挤压，组织发生完全动态再结晶，可以获得较好的力学性能；挤压后进行锻压变形，试样的室温抗拉强度和屈服强度分别比挤压状态提高13．5％和15％，延伸率下降33．3％；250℃的抗拉强度和屈服强度比挤压状态分别提高15％和41．4％。试样经过T6处理后，晶界附近析出相尺寸细小、分布均匀，室温抗拉强度和屈服强度分别达到365和335MPa。固溶强化和析出强化是导致T6状态试样拉伸强度提高的两个主要因素。     

热加工对铸造AM50镁合金显微结构和力学性能的影响

采用锻造和等通道转角挤压(ECAP)等技术研究了热加工对铸造AM50镁合金显微结构和力学性能的影响, 以改善该合金的力学性能.结果发现, ECAP对铸造AM50镁合金和锻造AM50镁合金两种显微结构的影响不同, 这是由于两种状态初始晶粒尺寸不同引起的.铸态AM50镁合金晶粒尺寸粗大, 经过ECAP工艺后, 晶界上出现大量平直滑移线;而锻态AM50镁合金经过ECAP工艺后, 晶粒进一步细化, 滑移线痕迹不明显.铸态AM50镁合金经过ECAP工艺后显微硬度从54.5提高到72.3, 锻造AM50镁合金经过ECAP工艺后显微硬度从60.3提高到81.9.铸造AM50镁合金经过锻造及ECAP工艺热加工后力学性能抗拉强度提高到320 Mpa, 同时延伸率保持在35%以上.     

Y对不同处理状态ZK31组织和性能的影响

通过对ZK31+x Y镁合金挤压态及固溶时效态的显微组织分析及力学性能研究,探讨了Y对ZK31+x Y镁合金组织和力学性能的影响。实验结果表明:Y的加入使得共晶相数量明显增加,挤压态强度随着Y的增加先增加后降低,当钇含量为0.5%时达到最大值332.4 MPa,延伸率先减小后增大,当钇含量为1.0%时,延伸率最小值11.1%;钇对时效硬度和力学性能影响不大;挤压态强度明显大于时效态,而时效态的延伸率明显大于挤压态。     

Effects of RE on Microstructures and Mechanical Properties of Hot-Extruded AZ31 Magnesium Alloy

Effects of rare earth (RE) additions on microstructure and mechanical properties of the wrought AZ31 magnesium alloy were investigated. The results show that, by adding 0.3%, 0.6% and 1.0% RE elements, the as-cast microstructure can be refined, and the as-cast alloys‘ elongation and tensile strength can be improved. After extrusion, the alloy with 0.3 % and 0.6% RE additions obtain a finer microstructure and the best mechanical properties, but the alloy with 1.0% RE addition has the coarse A1-RE compound particles in grain boundaries which decreased elongation and tensile properties. Usually, Rare earth (RE) elements were used to improve the creep properties of aluminium-containing magnesium pressure die cast alloys at elevated temperatures. In this paper, it is also found that the high temperature strength of extruded materials can be increased by RE elements additions.     

Pb对AZ91镁合金铸态显微组织及力学性能的影响

采用扫描电镜观察、电子探针分析及拉伸性能测试等方法研究了Pb的添加对AZ91合金显微组织和力学性能的影响。结果表明,Pb能够细化AZ91镁合金中的d—Mg和β-Mgl7Al12的晶粒,抑制二次B的析出,且Pb可改善β-Mgl7Al12相形态和分布。Pb通过细晶强化增加了合金强度和硬度,使合金的断裂机制从脆性解理断裂转变为准解理断裂。     

Microstructure and mechanical properties of A356 alloy with yttrium addition processed by hot extrusion

The effects of the rare earth element yttrium(Y) and hot extrusion on the microstructure and mechanical properties of A356 alloy were investigated by mechanical properties testing and microstructure observation. The results indicate that the addition of Y improves the microstructure of the as-cast alloy. The distribution of primary α-Al is uniform and orderly. The long needle-like eutectic Si phases and β-Fe phases turn to strips and short rods. When the content of Y increases to 0.2 wt%, the mean diameter of aAl(40.3 μm) and the aspect ratio of the eutectic Si phase(2.3) reach the minimum values, which are68.9% and 86.1% lower, respectively, than that of the alloy without Y addition. Under extrusion stress, the shape of the eutectic Si phase is changed from long rod-like to near grain-like after solution treatment.The size of the eutectic Si phase is significantly reduced. The needle-like β-Fe phases are squeezed and broken. The mechanical properties of the as-extruded alloy are significantly improved compared to the as-cast alloy. When the rare earth content is 0.2 wt%, the ultimate tensile strength, hardness and elongation of the alloy reach the maximum values, which are 328.2 MPa, 110.4 HV and 21.3%, respectively, and increase by 42.01%, 37.71% and 481.91%, respectively, in comparison to the as-cast alloy without Y addition.     

Sc对7056铝合金组织和性能的影响

对铸态合金进行了均匀化处理、挤压、固溶处理和时效处理,通过分析合金的化学成分,观察合金在不同状态的显微组织及析出相透射电镜(TEM)形貌,测试合金在热处理后的硬度和拉伸性能,研究了向7056铝合金中加入质量分数0.2%的Sc对合金组织和性能的影响.实验结果表明,Sc元素的加入可以明显细化组织晶粒,铸态晶粒由100~500 μm下降到50 μm左右;Sc元素的加入对合金的塑性有大幅度提高,时效处理后,合金的断后伸长率从10.82%增加到了13.60%;但屈服强度却由668 MPa下降到657 MPa.通过综合计算晶粒大小、析出相强化等因素,详细分析了Sc元素加入引起7056铝合金峰时效态屈服强度下降的原因.理论计算显示,向合金中加入质量分数0.2%的Sc元素时,峰时效处理后,合金的强度值会下降12.005 MPa,与试验值11 MPa接近.研究得到7056铝合金最佳的单级时效制度为120℃+16 h,峰值硬度和强度为195.2 HV和714 MPa,此时合金中主要强化相为圆盘状和短棒状的MgZn₂相,大小约为4~6 nm,同时存在球状的Al₃Zr相,大小约为20 nm.      

Evolution of microstructure and tensile properties of extruded Mg-4Zn-1Y alloy

In order to investigate the effect of extrusion on Mg-4Zn-1Y alloy, microstructure and mechanical properties were analyzed by optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, X-ray diffraction（XRD）, energy dispersive spectrum（EDS） and tensile testing.The results indicated that the microstructure was obviously refined by extrusion and dynamic recrystallization.The second phases were dynamic precipitated and distributed more dispersively through extrusion.W-Phases（Mg3Zn3Y2） were twisted and broken, while I-Phases（Mg3Zn6Y） were spheroidized by deformation.Twin bands were formed to achieve the large deformation and hinder the slip of dislocations effectively to improve tensile properties.The tensile strength and elongation of extruded Mg-4Zn-1Y alloy were 254.94 MPa and 17.9% respectively which were improved greatly compared with those of as-cast alloy.The strengthening mechanisms of the extruded alloy were mainly fine-grain strengthening and distortion strengthening.     

Microstructures,Mechanical Properties,and Wear Resistances of Thixoextruded SiCp/WE43 Magnesium Matrix Composites

Near-net shaping of Mg-RE alloy matrix composites has received increasing attention. In this work, stir casting followed by extrusion was adopted to fabricate Mg-RE alloy (WE43) matrix composites reinforced by micron-sized SiC particles. The microstructural evolutions of SiC_p/WE43 composites partially remelted from as-cast and extruded states were studied. Furthermore, the thixoformability of SiC_p/WE43 composites in different states was evaluated by thixoextruding a type of double-cup component. The microstructures of as-cast SiC_p/WE43 composites were optimized under the comprehensive effects of SiC particles and RE elements. The SiC_p/WE43 composite was fully recrystallized during hot extrusion, and the α-Mg matrix consisted of fine equiaxed grains. Although the as-cast SiC_p/WE43 composite consisted of satisfactory structures and can be successfully thixoextruded into the final component with good surface quality and no evidence of internal defects, the microstructures, Vickers hardness, tensile mechanical properties, and wear resistance were still inferior to those of the component thixoextruded from extruded composite. Moreover, the thixoextrusion process was analyzed schematically, and an ideal thixoforming process that should contain two stages was proposed.

     

均匀化工艺对2024高强度铝合金组织及性能的影响

通过采用金相显微镜、扫描电镜、力学拉伸试验机等检测手段,研究了2024高强度铝合金铸锭分别在均匀化温度480℃、495℃和510℃保温8h后经空冷和水冷方式处理后的组织及性能的影响.结果表明,经不同适合的均匀化工艺处理,铸态合金中的枝晶和非平衡低熔点共晶相逐渐溶解,晶界由连续分布逐渐转变呈不连续均匀分布状态.合金经49...     

Effect of mischmetal on mechanical properties and microstructure of die-cast magnesium alloy AZ91D

Effects of the mischmetal addition in range of 0.4 wt.% to 1.7 wt.% on the microstructure and mechanical properties of die-cast magnesium AZ91D were investigated to improve the elevated temperature mechanical properties of the alloy by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. The results revealed that mechanical properties of die-cast magnesium alloy AZ91D-0.4%MM at 100 oC were near to those of die-cast magnesium alloy AZ91D. The ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D at 170 oC were 178, 129 MPa and 20%, respectively. In comparison, the ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D-0.4%MM at 170 oC reached to 206, 142 MPa and 26%, respectively increased by 15.7%, 10% and 30%. Proper addition of mischmetal could enhance the mechanical properties at an elevated temperature, which was attributed to the formation of Al-RE phases with high thermal stability. Hence sliding of grain boundaries and cracks could be effectively hindered by Al-RE phases.     

ZK60合金粉末烧结和热挤压后的组织与性能

采用雾化法制得ZK60合金粉末,并用掺胶法制备ZK60合金棒材,研究热挤压后ZK60合金的微观组织、相组成及力学性能.结果表明:合金粉末主要由α-Mg固溶体构成,呈枝晶与等轴晶混合组织,晶粒尺寸5～10μm;在后续热挤压过程中粉末之间结合良好,晶粒进一步细化,同时合金基体中大量析出MgZn_2球形纳米颗粒;经T5(175℃保温12h)热处理后,析出相密度呈增加趋势.挤压变形后材料的屈服强度(σ_(0.2))、最大抗拉强度(σ_(UTS))和伸长率(δ)分别为286.3MPa、337.7MPa及5.6%;随后T5处理可进一步提高强度((σ_(0.2))=300.1MPa,σ_(UTS)=340.5 MPa),增加塑性(δ=12.3%).     

稀土Nd对AZ 31镁合金铸态组织和力学性能的影响

利用气氛电阻炉制备了AZ 31-xNd合金(x=0.05%,0.1%,0.2%,0.4%,0.6%),采用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)对不同Nd含量的实验合金进行了显微组织观察和分析,结果发现,Nd在AZ 31-xNd合金中形成了Al_3Nd和Mg_(12)Nd相,这些含Nd相导致AZ 31镁合金在凝固过程中的晶粒细化,从而提高了AZ 31镁合金的铸态室温力学性能,随着Nd含量的增加,合金的铸态室温抗拉强度极限和延伸率均先升高后降低.