Low-cycle fatigue behavior of permanent mold cast and die-cast Al-Si-Cu-Mg alloys

Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys. To feature their mechanical aspect of fatigue behavior, the low-cycle fatigue behavior of permanent mold cast and die-cast AI-Si- Cu-Mg alloys at room temperature was investigated. The experimental results show that both permanent mold cast and die-cast AI-Si-Cu-Mg alloys mainly exhibit cyclic strain hardening. At the same total strain amplitude, the diecast AI-Si-Cu-Mg alloy shows higher cyclic deformation resistance and longer fatigue life than does the permanent mold cast AI-Si-Cu-Mg alloy. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively.

Analysis of filling process of Ti6Al4V alloy melt poured in permanent mold during centrifugal casting process

Ti6Al4V hip joint was foundered and the filling process of the melt poured in permanent mould during the centrifugal casting process was analyzed and the mathematical model of the filling process was established. Furthermore, the mathematical model was validated with a wax model experiment. Calculating results show that the centrifugal field has an important influence on the filling process and the melt fills the mould with variational cross sectional area and inclined angle. The cross sectional area is in inverse proportion to the filling speed and its decreasing speed becomes fast with increasing rotating speed. The tangential value of the melt cross sectional free surface inclined angle is in direct proportion to the filling speed and the inclined angle increases with the filling length. Change curves of the cross sectional inclined angle and area were obtained by the wax model experiment when the rotating speeds were 60, 90 and 120 r/min respectively, which shows that the mathematical model is consistent with the experimental results. [

Antioxidation Study of Sm(Co, Cu, Fe, Zr)_z-Sintered Permanent Magnets by Metal Injection Molding

Antioxidation effects on Sm （Co, Cu, Fe, Zr）z-sintered magnets treated by different methods were studied through TGA and DTA. Microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets was analyzed through SEM and EDS. The results indicate that the antioxidation effect of the alloy powder treated in silane solution is better than that of the other methods. The alloy powders treated in stearic acid （SA） solution and polymethyl methacrylate （PMMA） solution can prevent powders from oxidation for a short period of time. Silane solution is not suitable for metal injection molding （MIM） because it severely damages the magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z-sintered magnets. SA solution can not only prevent powders from oxidizing in MIM, but also does not damage magnetic properties and microstructure of Sm（Co, Cu, Fe, Zr）z magnets. The oxygen content of Sm（Co, Cu, Fe, Zr）z-sintered magnets by MIM is 3300μg·g^-1.

Forming Mechanism of Gaseous Defect in Ti-48Al-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.

Characteristics and influence factors of mold filling process in permanent mold with a slot gating system

The main problems caused by improper gating are entrained aluminum oxide films and entrapped gas.In this study,the slot gating system is employed to improve mold filling behavior and therefore,to improve the quality of aluminum castings produced in permanent molds.An equipment as well as operation procedures for real-time X-ray radiography of molten aluminum flowing into permanent molds have been developed.Graphite molds transparent to X-rays are utilized which make it possible to observe the flow pattern through a number of vertically oriented gating systems.The investigation discovers that there are many influencing factors on the mold filling process.This paper focuses its research on some of the factors,such as the dimensions of the vertical riser and slot thickness,as well as roughness of the coating layer.The results indicate that molten metal can smoothly fill into casting cavity with a proper slot gating system.A bigger vertical riser,proper slot thickness and rougher coating can provide not only a better mold filling pattern,but also hot melt into the top of the cavity.A proper temperature gradient is obtainable,higher at the bottom and lower at the top of the casting cavity,which is in favor of feeding during casting solidification.

Characterization of Microstructure of Permanent Mold Cast Zinc Alloy ZA27

The microstructure of permanent mold cast zinc alloy ZA27 was examined by SEM and TEM after natural aging for 18 months. It was found that the primary a’ phase, peritectic and eutectic phases all decomposed into the equilibrium well-formed a+r| lamellae or irregular a+T| structure through cellular reaction. The cell colonies nucleated on the interdendritic eutectic T| layer and grew into the primary dendrites, thus first making the phase in the dendrite edges decompose, and then the a’ phase in the dendrite cores. The products from the a’ phase appeared in regular lamellae rather than irregular particles. In addition, a fine, dense transitional phase a’m containing 27.8 mass% Al, with a fee crystal structure and lattice parameter of about 0.4013nm, formed in lamellae. Copper was preferentially concentrated in Zn-rich n phase and existed in the form of Cu-rich e phase (CuZo,) particles, with hep crystal structure and parameters a=0.274nm, c=0.429nm and c/a=l .567.

Preparation of helicopter rotor counterbalance component by means of permanent-mold casting

Copper alloy was adopted to prepare helicopter rotor counterbalance component by means of permanent-mold casting. Process parameters were determined on the basis of theory calculation and computer numerical simulation. Through controlling mould temperature, pouring temperature and speed, the defects, such as gas cavity, shrinkage porosity, cold shut, can be effectively avoided. The results show that the best process parameters for smelting are as follows: pouring temperature is 1 100 ℃, pouring time is 14 s and opened mould time is 6 min. Mixture of 90% charcoal powder and 10% fluorite were selected as covering agent and 0.01% phosphorus copper acts as oxidizer. The density of rotor counterbalance component after casting in permanent-mold is 99.91% of its theory density. Mechanical properties are as follows: σb=315 MPa, σ0.2=143 MPa, δ=25%, HB=950. The mass deviation is between -5 g and +5 g, the curved surface distortion is less than 0.20 mm, and the largest tolerance of sectional thickness can be controlled between -0.10 mm and +0.10 mm.

Numerical simulation for permanent mold centrifugal cast TiAl exhaust valve

The filling and solidification in centrifugal field, as well as the forming mechanism of off-center porosities were summarized, based on the mathematical model established for the centrifugal cast TiAl exhaust valves. The calculated results show that the centrifugal field results in the phenomenon that the flow in the valve cavity consists of forward flow and backward flow. The unsymmetrical initial temperature field causes continuous unsymmetrical variation in the following solidification, which makes the final solidified region depart from the cavity axis and then leads to the occurrence of off-center porosity. A series of optimized parameters, including the entrance velocity of 0.6-1.3m/s, the rotation speed higher than 300r/min, 80mm or longer entrance length and 400℃ or higher preheated temperature of the mold, are suggested for the manufacture of permanent mold centrifugal cast TiAl exhaust valves.

Foundry technology and its applications of ductile iron castings produced by water-cooled copper alloy Mold

The high efficiency mechanized foundry technology of castings produced by using water-cooled copper alloy permanent mold has been systematically studied. Through the researching a Cu-Cr-Mg alloy with high conductivity and good combined mechanical properties used for making permanent mold was developed, and the basic design principles of the water-cooled permanent mold along with the control-range of relevant foundry processing parameters were also established. A cast production line equipped with water-cooled copper alloy mold was designed and fabricated for production of ductile iron automobile gear castings, This production line can consistently make automobile gear castJngs Jn QT500-15 and QT600-5 (Chinese Standard) grades of ductile iron with up to 95% casting success rate.

Diagnosis parameters of mold filling pattern for optimization of a casting system

For optimal design of a gating system,the setting of diagnosis parameters is very important.In this study,the permanent mold casting process was selected because most of the other casting processes have more complicated factors that influence the mold filling pattern compared to the permanent mold casting process,such as the surface roughness of mold,gas generation from the mold wash and binder of sand mold,and the gas permeability through a sand mold,etc.Two diagnosis parameters(flow rate difference and arrival time difference) of molten metal flow pattern in the numerical simulation are suggested for design of an optimum casting system with a permanent mold.The results show that the arrival time difference can be used as one important diagnosis parameter of the complexity of the runner system and its usefulness has been verified via making aluminum parts using permanent mold casting(Fig.9).

Mn/Fe比对Al-Mg-Si合金组织和性能的影响

以Al-Mg-Si合金为研究对象,采用金属型铸造研究Mn/Fe比对其组织和性能的影响。结果表明:Al-Mg-Si铸态合金组织中枝晶间存在α-Al基体和大量析出相,主要以Mg_(2)Si相为主,还存在少量的共晶Si相、AlFeSi相和Al(FeMn)Si相。随Mn/Fe比的增大,合金中的晶粒逐渐变得细小圆整,且由树枝晶向等轴晶发生转变。Mn可以促进铝合金中针状的β-AlFeSi相向骨骼状、颗粒状或块状的α-Al(FeMn)Si相的转变。当Mn/Fe比为0.5时,合金的热导率达到最大值181.08 W·m^(-1)·K^(-1)。当Mn/Fe比为1.0时,合金的晶粒尺寸最小且具有最佳的力学性能,抗拉强度、伸长率和硬度相较于Mn/Fe为0.2时分别提升17.45%、49.57%和27.48%,达到167.35 MPa、17.23%、HV 62.86。

铝合金制动钳金属型重力铸造工艺的多目标优化

利用数值模拟对铝合金制动钳金属型重力铸造过程进行分析,预测了钳体中缩松缩孔缺陷的分布情况,并分析其形成原因,改进了冷却方案,基于正交试验对工艺参数进行了多目标优化。得到最优工艺参数为:浇注时间28 s、浇注温度700℃、模具预热温度300℃、冷却水温度35℃。结果表明,优化后的制动钳铸件无缩松缩孔缺陷。通过生产试制验证了此优化工艺的可行性。

Influence of Mold Preheating and Silicon Content on Microstructure and Casting Properties of Ductile Iron in Permanent Mold

The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were investigated.The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased.The ductile iron with the carbon equivalent of 4.45 % and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 ℃.Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides.It is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon content.The suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 ℃ is the silicon content of 3.3% and carbon equivalent of 4.7%.

ZA27合金的微观组织

用SEM和TEM对金属型铸造并经 18个月自然时效的ZA2 7合金的微观组织进行了观察。结果表明 :ZA2 7合金凝固的初生相为富Al的树枝状α′相 ,随后在α′相周围形成一层富Zn的包晶 β相 ,最后剩余液体发生共晶反应 ,共晶 β优先依附于包晶 β相形核、长大 ,而共晶 η则在包晶 β相间形成一层薄膜 ,在有些区域则形成棒状共晶组织 ;在随后的冷却及时效过程中 ,β发生胞状分解形成规则的共析α +η层片组织或不规则的复杂形状组织 ,共析胞以共晶 η相为基形核 ,并向枝晶中心生长 ,使α′相也分解为层片α +η组织 ,当其生长被α′中心的连续分解所阻挡时 ,致使其芯部形成细小的α +η颗粒组织 ;富Cu的ε相存在于所有

华铸CAE软件在金属型铸造中的应用

随着计算机硬件水平的提高,铸造CAE软件对实际生产的指导作用越来越显著。本文介绍了华铸CAE软件金属型模块的基本功能和原理,并给出了在铝合金轮毂铸件上的应用实例,应用表明该软件能够准确地预测铝合金轮毂铸件中的缩松缩孔等铸造缺陷,辅助工艺人员进行工艺优化,指导实际铸件生产。

Ti-6-4合金熔体离心铸造过程中流态分析

针对金属型离心浇铸Ti 6Al 4V(Ti 6 4 )合金人工骨关节 ,对其充型过程进行了理论分析 ,得出了熔体离心充型过程中的层流判据以及熔体自由面倾角的变化规律。结果表明 ,离心力场下 ,熔体充型时可保持的层流长度随转台转速的提高而减小 ;熔体自由表面将发生倾斜 ,最终趋于竖直。此外 ,讨论了离心力场下铸件内部卷入性气孔和偏中心线缩松的产生原因及分布规律。

TiAl基合金排气阀金属型离心铸造过程内部缺陷分析

在所建立的数学模型基础上总结了 Ti Al基合金熔体离心力场下的充型规律。结果表明 ,离心力场的施加对于充型过程有重要影响 ,熔体以变化的截面面积和倾角填充铸型。熔体截面面积随充型长度的增大而减小 ,而熔体截面倾角随充型长度的增大而增大 ,这种变化在型腔入口附近表现得更加明显。此外 ,针对金属型离心浇铸 Ti- 48Al- 2 Cr- 2 Nb ( at% )合金汽车排气阀内部的常见缺陷 ,探讨了离心力场下排气阀内部卷入性气孔和偏中心线缩松的产生机理。

基于ProCAST的拉伸试棒的金属型铸造工艺分析

使用ProCAST软件,对铝合金金属型铸造拉伸试棒的充型和凝固过程进行数值模拟,在验证ProCAST模拟结果准确的基础上,分析充型凝固过程的各种物理场,确定浇注系统的合理性。试验结果表明,该浇注系统可以减少铸造缺陷,使铸造出的拉伸试棒的力学性能能够接近真实值。

浇注工艺对金属型铸造ZL114合金力学性能的影响

ZL114合金具有很高的力学性能和很好的铸造性能,广泛的应用于航空航天以及民用工业领域。采用正交实验法,研究浇注温度、模具温度、变质处理温度和变质剂加入量等四个工艺参数对金属型铸造ZL114合金力学性能的影响。结果表明,影响其力学性能的主要工艺参数是浇注温度和变质处理温度,综合力学性能最佳的工艺参数是浇注温度为700℃,变质处理温度为720℃,变质剂加入量为1%和模具温度为250℃。

粘结剂和添加剂对注射成型各向异性粘结NdFeB磁体的影响(英文)

研究了在取向磁场下由HDDR磁粉注射成型的各向异性粘结NdFeB磁体,分析了粘结剂和添加剂对各向异性粘结NdFeB磁体的密度、磁性能以及抗压强度的影响。通过磁粉表面改性,磁粉的抗氧化性能以及磁体的磁性能都得到提高。比较了6种粘结剂对磁体性能的影响,从中得到比较理想的粘结剂,并且考察了抗氧剂以及润滑剂加入量对于磁体性能的影响。试验中,混炼温度为205～215℃,注射温度为265℃,注射压力为5～6MPa,保压时间为5s,模具加热温度为80℃。制得的磁体的性能为:Br=0.72T,iHc=983kA/m,(BH)max=75kJ/m3。