变质ZA43合金中稀土的存在形式

通过电子探针附带扫描背散射电子成像(SEM)观察分析了ZA43合金的显微结构和相组成.利用电子探针对合金中各相的元素分布进行了分析.研究了变质ZA43合金铸态组织中含0.15%混合稀土的存在形式.实验结果表明,稀土元素主要分布于合金组织的晶界上,并以稀土金属化合物的形式存在.在枝晶中心和枝晶边缘没有发现稀土元素.稀土在α相的边缘含量较低,在η相中未见存在.ZA43合金经稀土调质,细化了合金晶粒.     

热处理对GWZ661变形镁合金组织与性能的影响

采用常规铸造和热形变相结合的工艺制备Mg-6Gd-6Y-1Zn四元镁合金,并对其显微组织和力学性能进行较系统的研究。结果表明:合金的铸态组织主要由α-Mg,Mg24(GdYZn)5和具有18R-LPSO结构的Mg12Y1Zn1相组成。合金热挤压过程中Mg12Y1Zn1相被拉长,呈长条状沿挤压方向排列,而14H-LPSO相则分布于Mg12Y1Zn1相之间。挤压态合金在高温固溶处理后,Mg12Y1Zn1相溶入基体,而基体中的14H-LPSO相增加。挤压态合金经固溶和时效(T6)处理后,显微组织中呈现18R-LPSO,14H-LPSO结构和β′沉淀颗粒共存。对挤压后的合金直接进行时效(T5)处理过程中也发生了β′沉淀,但14H-LPSO相体积分数没有T6态多。合金在T6态的性能最好,强度和塑性达到了良好的匹配。     

稀土Y对Mg-6Zn-1Mn合金显微组织和力学性能的影响

利用光学显微镜、X射线衍射仪、扫描电子显微镜、万能力学试验机等手段,系统研究了不同含量Y(1%~6%(质量分数))对Mg-6Zn-1Mn合金显微组织和力学性能的影响。结果表明,随着Y的不断增加,Mg-6Zn-1Mn系铸态合金主要物相演变规律为α-Mg+Mg7Zn3→α-Mg+I→α-Mg+W→α-Mg+X,这主要归因于不同的Zn/Y原子比。研究发现,当Y含量低于2%时,挤压可使晶界和晶粒内部析出细小弥散的第二相,同时提高了合金强度和室温延展性。而随着Y的进一步增加,第二相颗粒变大,且主要存在于晶界,热挤压过程中晶粒不易被挤碎,弱化了析出相与基体的界面能,最终使得挤压态合金综合力学性能降低。     

LPSO相增强Mg-6Gd-4Y-xZn合金的组织与力学性能

制备了3种LPSO相增强Mg-6Gd-4Y-xZn(x=1,2,3)(%,质量分数,下同)四元镁合金,研究了不同Zn含量对合金显微组织和室温力学性能的影响,并探讨了合金中LPSO相的形成与演变过程及其对合金的强化机制。研究结果表明,Mg-6Gd-4Y-3Zn合金的铸态组织主要由α-Mg和18R长周期结构相Mg12Y1Zn1相组成。若降低合金中的Zn含量,显微组织中会出现Mg24(GdYZn)5。3种合金的退火组织均由α-Mg、18R-LPSO和14H-LPSO相组成,且随着Zn含量的增加,合金中18R-LPSO相的体积分数增加且基体中14H-LPSO相的层片变粗。挤压态合金在T6和T5处理的过程中均发生了β'沉淀。随着Zn含量增加,合金Mg-6Gd-4Y-xZn(包括挤压态和时效态)在常温下的抗拉强度降低。显微组织中18R-LPSO相、细小弥散分布的14H-LPSO相和β'沉淀相共存方能实现理想的强化效果。     

ZA27合金部分重熔过程中组织的扫描电镜观察

用扫描电镜背散射电子成像技术，对经Zr变质处理的ZA27合金在半固态温度460℃部分重熔过程中的微观组织进行了观察，并对有关组织的成分进行了测定。结果表明，随着保温时间的延长，晶界处的共晶组织向初生晶内部扩散，趋于消失，晶粒由铸态时的等轴晶变为粒状晶。当保温10min时，未来得及溶入的共晶组织开始熔化，使组织分离为近粒状。到20min时，初生晶粒演变为粒径为40μm左右的球状颗粒，同时，晶粒中细小、弥散分布的η相由外到里逐渐长大，并伴有熔化现象。     

Zr变质SiCP/ZA27复合材料在部分重熔过程中的组织演变

用扫描电镜(SEM)背散射成像技术对Zr变质SiC_P/ZA27复合材料在部分重熔过程中的组织演变进行了研究,并与未变质复合材料及基体合金作了对比。结果表明:经0.2 wt% Zr变质的SiC_P/ZA27复合材料在460℃加热过程中(0min~30min),其基体组织依次经历了晶臂的快速合并,晶粒的长大,晶界区域的熔化、组织分离,最后经球状化形成触变成形所需的粒径较为均匀、细小、圆整的半固态浆料,在随后的保温过程中(30 min~80 min)未发现明显的粗化现象;未变质复合材料则形成相互连接的不规则组织,即使经长时间的保温(80 min),也未全部球状化;基体合金组织的分离快于变质复合材料,但在保温中的晶粒粗化却较为严重。加热初期晶粒的快速粗化是由共晶组织向晶内的迅速扩散引起的。本文作者从相变角度分析了组织的演变过程。     

热处理对粉末热挤压法制备6061铝合金强度和塑性的影响

研究了单级固溶及峰值时效处理对粉末热挤压法制备6061铝合金显微组织及室温力学性能的影响,观察了合金挤压态、固溶态及时效处理后的显微组织,并对其力学性能进行了测试.结果表明:挤压态材料的晶粒均匀细小,基体合金中存在大量的第二相颗粒,主要为Mg2Si相;热挤压后的6061铝合金经固溶时效处理(530℃×1 h水冷+170℃×6 h)后,晶粒内部析出大量的β″(Mg5Si6)相,并伴有少量棒状的β’(Mg2Si)相析出,拉伸强度和延伸率分别为311 MPa和10%,相比挤压态铝合金,其拉伸强度提高了近160%.     

Mg-Y-Nd-Zr-Zn 铸造镁合金组织与性能研究

目的研究Mg-Y-Nd-Zr-Zn镁合金的显微组织演变和力学性能。方法采用金相显微镜(OM)、扫描电镜(SEM)、能谱(EDS)以及电子万能实验机等,研究了Mg-Y-Nd-Zr-Zn镁合金铸态及T6态的组织和性能。结果 Mg-Y-Nd-Zr-Zn铸态合金组织由含Y的镁基固溶体、网状富稀土的共晶相和颗粒状的Zr单质组成;经525℃×10 h+200℃×16 h处理后,晶界网状第二相消失,细小的Mg-RE金属间化合物从基体中析出,弥散分布于晶界及晶内。结论 T6处理后,Mg-Y-Nd-Zr-Zn合金力学性能显著提高,抗拉强度、屈服强度和断裂伸长率分别为306 MPa,230 MPa和3.5%。     

固溶时效深冷复合处理对ZCuAl10Fe3Mn2合金微观组织和热疲劳性能的影响

研究T6处理、深冷处理和T6+深冷处理对ZCuAl_(10)Fe_3Mn_2合金微观组织、力学性能以及在室温至450℃下的热疲劳行为。通过XRD,OM,SEM,EDS对合金组织和裂纹形貌进行观察分析。结果表明:T6+深冷复合处理工艺能够显著改善ZCuAl_(10)Fe_3Mn_2合金的力学性能和微观组织。与T6处理相比,其抗拉强度、硬度以及伸长率分别提高了7.28%,16.96%和23.53%;其α相进一步细化且分布更加均匀,位错密度增加,使得合金整体的组织均匀性、致密性更好。综合性能的提高也有效地提高了合金的热疲劳性能,其抗热应力和氧化腐蚀的能力增强。在相同冷热循环次数下,疲劳裂纹长度最短,裂纹生长速率最慢。     

喷射成形高锰ZA35合金的工艺及组织研究

利用优化工艺参数的喷射成形技术制备含Mn3.5%(质量分数,下同)的ZA35合金坯,比较了铸态和喷射成形态合金的微观组织.研究表明:喷射成形态合金晶粒细小,组织分布均匀;元素Mn在铸态组织中主要以大量富Mn独立硬化相分布于晶界或晶界附近,喷射成形合金组织中富Mn相消失,元素Mn溶入基体,固溶度明显提高.元素Mn在铸态和喷射成形态合金基体中分布规律一致,即在α富铝相中的固溶度显著高于在η富锌相中的固溶度.热挤压后,喷射成形3.5%Mn-ZA35中有类似纳米级晶须状和颗粒状的MnAl6析出.     

Influence of boron on the microstructure and mechanical properties of Al-11.6Si-0.4Mg casting alloy modified with strontium

Abstract

The influence of the addition of Al-1B master alloy on the microstructure and mechanical properties of Al-11.6%Si-0.4%Mg alloy modified with 0.030%Sr has been investigated. The mechanical properties and fracture behaviour of the alloys as cast and after T6 heat treatment with three different melt treatments (no treatment; 0.030%Sr modifying treatment; and 0.030%Sr + 0.028%B combined melt treatment) were also compared. Al-1B master alloy has a strong action in refining the dendritic structure in near eutectic Al-Si casting alloys modified with Sr. The Sr+B combined melt treatment can improve considerably the mechanical properties of the alloys, both as cast and after T6 heat treatment. Fracture modes of the alloys with the Sr modifying treatment and the Sr+B combined melt treatment are typically ductile. However, fractographs indicate that the alloy with combined melt treatment suffered greater ductile deformation before fracture. The Sr+B combined melt treatment significantly improves the mechanical properties of near eutectic Al-Si casting alloys.     

Effects of Charge Inheritance on High Zn-Al Based Alloy

The effects of several kinds of charges on microstructure and mechanical properties of ZA27zinc alloy have been Studied. Experimental results show that a certain amount of the mechining charge, granular charge and remelting charge treated in suitabIe way can increase greatly the mechanical properties of ZA27 alloy. It is thought that the charges possess microstructure inheritance to ZA27 alloy, so cause the property changes according to the viewpoints of casting alloy inheritance.     

Microstructure and mechanical properties of Al–Si–Mg–Cu–Ti alloy with trace amounts of scandium

The effect of Sc on the microstructure and mechanical properties of Al–Si–Mg–Cu–Ti alloy was investigated. Results obtained in this research indicate that, with increasing Sc content, the microstructure of the investigated alloys exhibits finer equiaxed dendrites with rounded edges and the morphology of the eutectic Si shows a complete transition from a coarse needle-like structure to a fine fibrous structure upon modification of eutectic Si. Subsequent T6 heat treatment had further induced the precipitation of nano-scaled secondary Al₃(Sc, Ti) phase, as well as spheroidisation of eutectic Si. Combined with T6 heat treatment, the ultimate tensile strength, yield strength, percentage elongation and hardness were achieved in 0.20?wt-% Sc-modified alloy.     

Al-Zn-Mg-Cu合金半固态成形的研究现状与应用

半固态成形技术为实现Al-Zn-Mg-Cu系高强铝合金"以铸代锻"的目标提供了有效途径。主要综述了Al-Zn-Mg-Cu合金半固态制浆与成形技术、半固态成形合金的成分调控、微观组织结构与性能等方面的研究现状与进展,同时结合笔者所在学术团队的研究经历,对半固态成形件的组织和性能进行了简要分析。详细综述了Al-Zn-Mg-Cu合金半固态制浆和成形方法,着重介绍了环缝式电磁搅拌技术、蛇形通道浇注法及复合式半固态成形技术。进而综述了Al-Zn-Mg-Cu半固态成形合金的成分及微观组织结构调控方面的研究进展,介绍了合金成分调控及热处理工艺优化对性能的积极影响,分析比较了Al-Zn-Mg-Cu合金半固态成形后的微观组织和力学性能的研究现状。最后,对该成形方向的研究和应用现状进行了总结,分析了其需要解决的主要问题,并对其发展方向进行了展望。     

变质和热处理对高强度铸造Al-Cu-Si-Mn合金组织和性能的影响

通过变质处理和热处理实验,研究了不同的Ti变质加入量和固溶时效处理对高强度铸造Al-Cu-Si-Mn合金组织和性能的影响.结果表明,试验材料的铸态组织为粗大的α(Al)固溶体和其晶界分布的θ(Al2Cu)及T(Al12CuMn2)相,加入0.15%～0.2%Ti变质处理可以细化试验材料的铸态组织,变质处理后进行固溶和时效处理,组织由α(Al)固溶体和其晶内弥散分布的二次T相组成,晶界处残留有未完全固溶的T(Al12CuMn2)相,组织中出现α(Al)晶界无析出区.Ti变质处理高强度Al-Cu-Si-Mn合金组织对壁厚效应的敏感性不明显.     

T4 热处理对石膏型 AZ91 铸造镁合金组织和性能的影响

用石膏型熔模铸造技术,成功制备了AZ91镁合金铸件.用金相显微镜(OM)、扫描电镜(SEM)、能谱(EDS)以及电子万能实验机等,研究了AZ91镁合金铸态及T4热处理态的显微组织演变和力学性能.结果表明,分布在铸态AZ91镁合金晶界的网状β-Mg17Al12相在T4热处理过程中逐渐溶解,铸态和T4热处理态中均存在大量的A18Mn5化合物,T4处理后,其力学性能显著提高.     

Influence of modification, solidification conditions and heat treatment on the microstructure and mechanical properties of A356 aluminum alloy

The effects of casting thickness, modification and heat treatment on the microstructure and mechanical properties of A356.2 alloy have been investigated. Experiments were conducted with unmodified, Sr-modified (0.02% Sr) and Sb-modified (0.2% Sb) on both sand cast test bars with various thicknesses (from 3 to 9 mm) and permanent mold cast test bars.The microstructural changes associated with these treatments have been studied by optical metallography, scanning electron microscopy (SEM) and image analysis.The tensile properties of all samples were determined and the relationship between cooling rate, modification and heat treatment has been investigated.The results show that modification has a beneficial effect on microstructure and improves the mechanical properties of the alloy. Modification has a major role in controlling the kinetics of the spheroidisation of silicon particles during heat treatment. Tensile properties improved more with heat treatment than with modification or cooling rate.Antimony is effective on mechanical properties at higher solidification rates, while Strontium is more effective at lower solidification rates.     

Microstructural and mechanical features of aluminium semi-solid alloys made by rheocasting technique

The rheocasting process applied by Swirled Enthalpy Equilibration Device (SEED) technique relies on rapid extraction of a controlled quantity of heat from the liquid aluminium alloy via mechanical agitation to form the semi-solid slurry that can be formed under pressure. Microstructural characteristics of both conventional and semi-solid A357 castings under T6 heat treatment conditions were examined using optical and scanning electron microscopy. The fatigue and tensile experiments were applied to evaluate the effect of SEED technique on the mechanical properties of T6-A357 semi-solid alloys and conventional castings. The results showed that the rheocasting–SEED technique has proved successful in producing optimum microstructure of Al–Si–Mg semi-solid alloys providing an excellent combination of quality and mechanical performance as compared to conventional technique.

This paper is part of a Themed Issue on Aluminium-based materials: processing, microstructure, properties, and recycling.     

Effects of Sn addition on as-cast microstructure, mechanical properties and casting fluidity of ZA84 magnesium alloy

The effects of Sn addition on the as-cast microstructure, mechanical properties and casting fluidity of the ZA84 magnesium alloy are investigated. The results indicate that adding 0.5–2.0 wt.%Sn to the ZA84 alloy not only can result in the formation of Mg₂Sn phase but also can refine the Mg₃₂(Al, Zn)₄₉ phase and suppress the formation of Mg₃₂(Al, Zn)₄₉ phase, and with the increase of Sn amount from 0.5 wt.% to 2.0 wt.%, the morphology of Mg₃₂(Al, Zn)₄₉ phase gradually changes from coarse continuous and/or quasi-continuous net to relatively fine quasi-continuous and/or disconnected shapes. In addition, adding 0.5–2.0 wt.%Sn to the ZA84 alloy can improve the tensile and creep properties, and casting fluidity of the alloy. Among the Sn-containing ZA84 alloys, the ZA84 alloy added 1.0 wt.%Sn exhibits the best ultimate tensile strength, elongation and casting fluidity while the ZA84 alloy added 2.0 wt.%Sn has the best yield strength and creep properties.     

金属型重力铸造高强度铝铜合金

目的 针对铝铜合金热裂敏感性高、难以进行金属型铸造的难题,研究其合金成分、铸造工艺、组织与性能的关系。方法 首先充分分析铸造铝铜合金的凝固机制与特点,在ZL205A合金基础上,设计了新型合金成分以及两种铸造试样模,经过熔炼、铸造与热处理,获得砂型铸造与金属型铸造试样,进行力学性能测试、组织分析,并观察试样的抗热裂性。结果 两种铸造试样都获得了较高的力学性能,铸态及T6态全部为等轴晶组织,成功避免了热裂问题,并提高了合金的力学性能;金属型铸造试制了油马达铸件。结论 证明了通过铝铜合金的成分优化设计,以及含钪复合细化剂的合理匹配,采用金属型铸造获得等轴晶组织,进而避免粗大枝晶组织,是克服热裂问题的关键,从而实现金属型铸造高强度铝铜合金。