镁合金半固态压铸触变成形技术的研究与进展

介绍了镁合金半固态触变成形技术中的三个关键技术：非枝晶组织半固态浆料的制备、坯料的二次加热、半固态触变压铸成形.并综述了镁合金半固态压铸触变成形技术的研究现状和发展前景.     

等轴组织铝合金触变成形工艺的研究

与树枝晶显微组织合金相比，等轴组织的合金在半固态下表现出更低的流动阻力，这种触变行为(即在无外力作用下表现为类固体特征，而在剪切条件下列表现为类液体特征)是触变工艺的基础。今日人们普遍认为半固态的触变成形是一种新的最终成形加工工艺。对于工业生产，触变成形工艺有许多优点，诸如，可成功地生产内部缺陷较少的高质量零件；适合于少切副加工；具有可与高压模铸相比拟的高生产率；并且由于省去了传统的加热溶化工序而节能。触变成形工艺包括感应线圈设计、坯料再次加热过程，坯料处理、坯料充入模具型腔和成形件凝固等步骤。本文给出了生产具有良好机械性能之最终成形产品的触变成形过程各阶段的综述，并且应用触变成形工艺生产出高强度空气压缩机零件。     

新型半固态用铝合金的触变成形研究

研究了Al-6Si-2Mg半固态成形中,电磁搅拌连铸、二次加热和压铸的工艺以及各工序得到的微观组织和力学性能.由于该合金是针对半固态触变成形专门设计,所以该合金在各工序中都表现出良好的工艺性能.通过优化工艺,试验最终得到了外观完整,性能优良的压铸件,为半固态触变成形的工业应用打下了基础.     

金属半固态成形工艺概述

分析了非枝晶半固态金属的特性和半固态金属的成形特征，在此基础上，较详细介绍了金属半固态成形工艺，包括触变成形和流变成形技术。同时，分析了各种成形工艺的优、缺点以及应用范围。     

热处理对半固态触变成形镁合金组织与力学性能的影响

研究了固溶处理对金属型铸造成形及半固态触变成形镁合金AZ91D组织与性能的影响。半固态触变成形使镁合金组织中的α-Mg固溶体由树枝状转变为球状,其抗拉强度和伸长率得到大幅度的提高;同时,由于固溶强化作用使镁合金的抗拉强度、伸长率与普通金属型铸造成形相比提高幅度达51.6%和248.11%。     

TiCp／7075铝基复合材料的半固态触变成形

用原位反应喷射沉积法制备TiCP/7075铝基复合材料, 并进行半固态触变成形试验,研究了TiCP/7075铝基复合材料的半固态触变成形性及其成形后的微观组织与力学性能.结果表明,该材料具有良好的半固态触变成形性,在成形压力仅为20～25 MPa的条件下,就能够进行半固态触变成形.在625 ℃进行半固态触变成形后,其组织仍能保持均匀的等轴晶特征,平均晶粒尺寸为30～40 μm;半固态触变成形试件经T6处理后其硬度HRB为82～85.     

液相线半连续铸造7075Al合金二次加热与触变成形

研究了液相线半连续铸造的7075Al合金半固态浆料在不同温度下的液固相比、二次加热组织、触变成形性,以及热处理前后成形件的力学性能。结果表明,7075Al合金触变成形液相比为30%-50%时对应的温度区间为600-620℃,二次加热可以将液相线半连续铸造7075Al合金锭坯中的蔷薇状和近球状组织转化为球形晶粒组织,适合于半固态加工,组织最佳的条件是加热温度580℃左右,保温时间15-30min,及加热温度600℃左右,保温时间5-15min.加热到600℃,保温15min后7075合金流动性成形性非常好,闭模锻造完全可以半固态成形,未经热处理的7075Al合金成形件强度极限达357.9MPa,T6热处理后强度极限达468MPa。     

热处理对半固态触变成形镁合金组织与力学性能的影响

研究了固溶处理对金属型铸造成形及半固态触变成形镁合金AZ91D组织与性能的影响。半固态触变成形使镁合金组织中的α-Mg固溶体由树枝状转变为球状，其抗拉强度和伸长率得到大幅度的提高；同时，由于固溶强化作用使镁合金的抗拉强度、伸长率与普通金属型铸造成形相比提高幅度达51．6％和248．11％。     

铝合金半固态加工技术的应用研究

重点介绍了近年来在铝合金半固态坯料制备方面的研究进展以及在半固态触变成形技术工业应用方面的研究开发工作,如复合电磁搅拌制备半固态浆料、多流电磁搅拌半固态连铸技术、铝合金半固态触变压铸成形、铝合金半固态触变模锻成形等,并就其可能的应用领域及发展状况如难铸造合金的铸造成形、变形合金的直接铸造成形、活塞合金的加工成形、变形铝合金的塑性加工进行了讨论。     

半固态流变成形的技术关键与新进展

早期的半固态加工技术以触变成形为主,但流变成形越来越受到企业界的欢迎,正在成为半固态加工技术领域的新亮点.目前已经利用半固态流变成形生产了包括黑色金属在内的多种零件,显示了光明的应用前景.但是,半固态流变成形要达到规模应用,必须解决模具材料、半固态浆料的定量浇注及工艺过程的自动控制3大问题.     

ZL112Y半固态压铸摩托车零件的组织和性能研究

为了研究半固态高压铸造成形技术对零件的组织和力学性能的影响，对ZL112Y铝合金在半固态下压铸成形JH70型摩托车发电机支架零件进行了本体解剖，制作了金相观察试样和拉伸试验非标试样，观察了试样不同部位的组织特征，测定了零件的强度、塑性和硬度。试验结果表明，半固态压铸成形零件具有消除高压铸造零件的内中孔洞和组织疏松的特点，因此可以通过热处理来提高零件的力学性能。该半固态压铸零件的最高抗拉强度、平均抗拉强度，平均屈服强度，平均伸长率和平均硬度HRB值比液态成形零件分别提高了60.10%、50.83%、41.52%、514.29%、12.41%。     

A study on a thixoforming process using the thixotropic behavior of an aluminum alloy with an equiaxed microstructure

Alloys with an equiaxed microstructure exhibit significantly lower flow resistance in the semisolid state than alloys with a dendritic microstructure. Their thixotropic behavior (solidlike in the unperturbed state and liquidlike during shearing) has been the basis for a thixoforming process. It is accepted today that thixoforming is a new net-shaped manufacturing technology in which the billet is heated to the semisolid state with coexisting solid-liquid phases. The thixoforming process has some industrial advantages, such as the successful fabrication of high-quality components with fewer inner defects, suitable for less machining, high productivity comparable to high-pressure die casting, and being an energy-saving system without the conventional melting process. It consists of inductive coil design, a billet reheating process, billet handling, filling into the die cavity, and solidification of the thixoformed part. This work presents an overview of all the detailed stages in the thixoforming process to manufacture the net-shaped product with good mechanical properties. An air compressor part with high strength has been fabricated by the thixoforming process.     

Induction heating of semisolid billet and control of globular microstructure to prevent coarsening phenomena

An important step in the thixoforming process is the induction heating of the raw materials to the semisolid state. Using this technology, the process behavior is satisfactory from the point of view of reproducibility and temperature control. Therefore, the objectives of this study are to define the correct relationship between coil length and billet length for uniform induction heating and to present the optimal reheating conditions suitable for the thixoforming process (or to secure a fine globular microstructure without liquid segregation). The optimal inductive coil on the induction heating process of semisolid billet machined to 76 mm diameter and 90 mm length to reduce the temperature gradient of the billet and to obtain the globular microstructure was theoretically designed and the suitability of the designed coil dimensions verified by reheating experiments. The globular microstructures of semisolid billet in heating and holding processes were controlled to prevent the coarsening phenomena of Al-7%Si-0.3%Mg alloy and to apply to the thixoforming process. In addition, the effects of the history of processing and induction heating parameters such as reheating time, holding time, holding temperatures, capacity of the induction heating system, and adiabatic material size on the globularization were investigated. It was concluded that in the case of a three-step reheating process, the final holding time is the most important factor and 2 min is suitable to maintain a globular microstructure.     

Numerical simulation of thixoforming

Processing of alloys and composites in the solid plus liquid range has advantages over casting, forging, and powder metallurgy techniques. The sensitivity of semisolid slurries to temperature variations and their history and rate dependent behavior, however, make process design and control difficult. Precise selection of die velocity, process temperature, and die design is necessary to produce satisfactory products. Therefore, a computational capability for the prediction of the rheological behavior of semisolid materials would be an invaluable tool in process design. This work presents preliminary results on numerical simulations of thixoforming operations. Constitutive models that are able to describe qualitatively the transient flow behavior of semisolid materials are implemented in a finite element program. Simple but realistic thixoforming operations are simulated. Weaknesses of currently available constitutive models and numerical techniques are identified and discussed. This paper was originally presented at the Symposium “Paniculate Materials in Rheological Applications,” TMS 1993 Fall Meeting, Materials Week Program.     

Semi-solid extrusion of aluminum alloy ZL116

The semi-solid forward-extruding feasibility of reheated ZL116 alloy cast by the near-liquidus semicontinuous casting process was studied by analyzing the microstructures and properties of forward-extruded bars. The results show that the microstructure of the ZL116 alloy billets cast by near-liquidus semi-continuous casting is mainly made up of homogeneous, fine global- or rosette-shaped grains. The microstructure of the billets, reheated and held at 575℃, contains stable and net-spherical grains which are suitable for semi-solid thixoforming. The semi-solid forward-extruded bars of the ZL116 alloy billet are facially smooth, microstructurally fine and homogeneous. Therefore the feasibility of semi-solid forward-extrusion of ZL116 alloy is thus excellent.     

ZL101铝合金半固态微挤压流动性实验研究

从微塑性成形技术入手,结合半固态金属良好的成形性能,对半固态金属ZL101铝合金进行正挤压成形实验研究,探讨了半固态金属微成形流动性性能,分析比较了温度、挤出直径、工作带对金属流动性的影响.实验结果表明:微成形条件下,半固态成形可以大大降低挤压载荷;半固态微成形出现了类似尺度效应的现象;工作带越小,挤出长度越长.     

Mg对反重力铸造ZL116合金组织和性能的影响

通过OM、XRD以及室温拉伸试验等手段,分析了Mg对反重力铸造ZL116合金显微组织和力学性能的影响。结果表明,随着Mg含量提高,ZL116合金的抗拉强度有所提高,伸长率基本没有变化。反重力铸造方式中差压铸造的ZL116合金力学性能最优,低压铸造次之,调压铸造的力学性能差于重力铸造。随着Mg含量提高,ZL116合金中的强化相Mg2Si含量也随之增加,最终导致ZL116合金抗拉强度提高。     

半固态亚共晶铝硅合金二次加热状态检测

采用浸入法研究了半固态亚共晶铝硅合金的二次加热状态及其触变性能。通过探头浸入坯料深度、浸入坯料时间以及作用在探头上的载荷等参数表征量化了半固态合金坯料在二次加热过程中的“软度”,即二次加热状态。根据实际情况提出了软度计算公式:S=KD/T及试验合金适于触变成形的软度范围:183相似文献   

ZL201合金挤压铸造薄壁筒形件的组织与性能

采用挤压铸造工艺加工出了ZL201合金薄壁筒形件，并对其组织与性能进行了研究。结果表明：ZL201合金适合于用挤压铸造工艺生产薄壁中、小型工件；经济压铸造工艺加工出的薄壁筒形件几乎没有铸造缺陷，强度比砂型铸造提高约54％，伸长率提高约17％，显微组织比砂型铸造细密均匀。在挤压铸造过程中，薄壁筒形件的塑性变形由外向里进行，显微组织呈梯度变化。     

Microstructure and properties of mechanical alloying particles reinforced aluminum matrix composites prepared by semisolid stirring pouring method

Aluminum matrix composites reinforced with mechanical alloying particles(SiC_p) were fabricated by the semisolid stirring pouring method. The inf luence of mechanical alloying particles and Mg on the microstructure and mechanical properties of the composites was investigated by means of optical microscopy(OM), X-ray diffraction scanning(XRD), electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Results show that the addition of Mg converts the agglomerate mechanical al oying particles in ZL101 matrix composites into dispersed distribution in ZL101-Mg matrix composites, large matrix grains into f ine equiaxed matrix grains, and eutectic phase into f ine particles. So the mechanical properties of ZL101-Mg matrix composites are better than those of ZL101 matrix composites. The mechanical properties of ZL101/ZL101-Mg matrix composites are gradually increased with the increase of the volume fraction of mechanical alloying particles. When the volume fraction of mechanical alloying particles is 3%, the Vickers hardness and ultimate tensile strength of the ZL101/ZL101-Mg matrix composites reach their maximum values.