Primary phase evolution of rheo-processed ADC12 aluminum alloy

The primary phase evolution of ADC12 aluminum alloy rheo-processed by mechanical rotational barrel system was studied by differential scanning calorimetry（DSC）, optical microscopy（OM） and scanning electron microscopy（SEM）. The semisolid slurry analyses show that the solid fraction of ADC12 aluminum alloy increases from 0.38 to 0.43 while the roundness decreases from 0.45 to 0.38 with increasing the rotational speed from 30 to 120 r/min. When the pouring temperature decreases from 620 to 580 °C, the primary α（Al） morphology changes from spheroidal to rosette-like. Besides, the average particle size of primary phase and solid fraction increase with the decrease of pouring temperature. By rheo-diecasting process, the components with fine, spherical and uniformly distributed primary α（Al） particles were obtained, and the best microstructure was contained at the pouring temperature ranging from 595 to 605 °C. The rheo-processing feasibility of ADC12 aluminum alloy can be explained by the grains controlled growth theory, and the semisolid slurry obeys the Mullins-Sekerka criterion when solidifying in the high pressure die casting machine.

Feasibility of semi-solid die casting of ADC12 aluminum alloy

The feasibility of semi-solid die casting of ADC12 aluminum alloy was studied. The effects of plunger speed, gate thickness, and solid fraction of the slurry on the defects were determined. The defects investigated are gas and shrinkage porosity. In the experiments, semi-solid slurry was prepared by the gas-induced semi-solid （GISS） technique. Then, the slurry was transferred to the shot sleeve and injected into the die. The die and shot sleeve temperatures were kept at 180 ℃ and 250 ℃, respectively. The results show that the samples produced by the GISS die casting give little porosity, no blister and uniform microstructure. From all the results, it can be concluded that the GISS process is feasible to apply in the ADC12 aluminum die casting process. In addition, the GISS process can give improved properties such as decreased porosity and increased microstructure uniformity.

Microstructure of semi-solid ADC12 aluminum alloy adopting new SIMA method

A semi-solid microstructure of ADC12 aluminum alloy containing spherical solid particles was studied.A new strain-induced melt activation(SIMA) process was proposed.In the treatment,chips were cut from ADC12 ingot by lathe machining and the plastic deformation was produced through cutting.The chips were put into a metal mold and compressed into a billet at 473 K.The microstructures of chip and billet were studied.The effect of the isothermal treatment on the semi-solid microstructure evolution of ADC12 aluminum alloy prepared by the new method was analyzed.A series of heating treatments were carried out from 823 to 838 K.The effects of heating temperature on microstructures were studied.The experimental results show the ADC12 aluminum alloy prepared by the new method can reap homogeneous and spherical grains at 828 K.The average grain size is about 82 μm.Also,the grain microstructure obtained by the present process is better than the traditional one.These results prove that the ADC12 aluminum alloy can be applied to semi-solid processing with the new SIMA method.

船舶柴油机气缸盖的FSW加工及接头组织性能分析

采用搅拌摩擦焊单面对接焊方法进行了新型铝合金ADC12Y0.3柴油机气缸盖的焊接,并进行了接头的内部缺陷、显微组织、力学性能和耐腐蚀性能的测试与分析。结果表明,接头无明显缺陷、力学性能和耐腐蚀性能较好,接头室温抗拉强度达262 MPa,接头系数达93%,接头腐蚀电位较母材负移了11 m V。

工艺参数对ADC12铝合金压铸件微孔缺陷与力学性能的影响

以ADC12压铸铝合金为研究对象,研究了浇注温度、高速切换点及压射速度等压铸工艺参数对ADC12铝合金压铸件微孔缺陷和力学性能的影响规律,分析了铸件的密度、微观组织和力学性能。结果表明,铸件的力学性能随着浇注温度的升高和压射速度增加先增高后降低,随高速切换位置增加而降低,同时,铸件内微孔数量随着高速切换位置和压射速度增加而增大。综合考虑,浇注温度为680℃,高速切换点位置为450 mm,压射临界速度为2.7 m/s时,铸件的微孔缺陷最少、力学性能最好。

不同热处理对ADC12压铸铝合金组织和力学性能的影响

以ADC12压铸铝合金化学成分为基础,在合金中加入了额外的2%与4%Cu,并进行了不同的热处理工艺研究,探讨了铝合金在无鼓泡缺陷时最佳的固溶处理温度、时间以及组织性能特点。结果表明:避免ADC12铝合金压铸件在热处理过程中表面鼓泡缺陷的最高温度和时间为490℃/0.25 h,若在更高的温度或更长时间进行热处理,则铸件会产生鼓泡缺陷。添加Cu的ADC12铝合金,在460~490℃固溶处理时,硬度随着Cu含量的增加而增大,而强度却随着Cu含量的增加而降低。当铝合金的高温强度大于12.54 MPa时,不会发生表面鼓泡缺陷。

ADC-12再生铝合金稀土Y变质作用研究

本文研究稀土Y不同含量对商用ADC-12再生铝合金的显微组织和力学性能的影响,样品通过真空感应熔炼钢模浇铸。实验证明:稀土Y对ADC-12再生铝合金显微组织和力学性能有良好促进作用。添加稀土Y后,共晶Si相由片状或血小板状转变为网状或点状,α-Al相逐渐变得圆整,且呈现均匀分布状态,β-Fe相由尺寸较大的粗壮针状相变为小尺寸鱼骨状相。但当稀土Y含量增加过峰值时,细化作用逐渐减弱,Al2Si2Y相以粗块状出现在基体中,β-Fe相长大平均面积达到7.04μm^(2),力学性能降低。实验结果表明再生铝合金熔炼过程中,添加0.5%的稀土Y,即可有效改善产品的质量和性能。

Chip morphology and cutting temperature of ADC12 aluminum alloy during high-speed milling

The ADC12 aluminum alloy is prone to severe tool wear and high cutting heat during high-speed milling because of its high hardness.This study analyzes the highspeed milling process from the perspective of different chip morphologies.The influence of cutting temperature on chip morphology was expounded.A two-dimensional orthogonal cutting model was established for finite element analysis(FEA)of high-speed milling of ADC12 aluminum alloy.A theoretical analysis model of cutting force and cutting temperature was proposed based on metal cutting theory.The variations in chip shape,cutting force,and cutting temperature with cutting speed increasing were analyzed via FEA.The results show that,with the increase in cutting speed,the chip morphology changes from continuous to serrated,and then back to continuous.The serrated chip is weakened and the cutting temperature is lowered when the speed is lower than 600 m·min^(-1)or higher than 1800 m·min^(-1).This study provides a reference for reducing cutting temperature,controlling chip morphology and improving cutting tool life.

铸造工艺对ADC-12再生铝合金显微组织和力学性能的影响

本文采用钢模浇铸和离心浇铸真空熔炼商用ADC-12再生铝合金,研究铸造工艺对ADC-12再生铝合金的显微组织和力学性能的影响。结果表明:离心浇铸对ADC-12再生铝合金显微组织和力学性能有良好促进作用,共晶Si相由片状或血小板状转变为网状或点状,α-Al相逐渐变得圆整、轮廓清晰且分布均匀,β-Fe相由粗大长针状转变为聚集的圆球状;相比钢模浇铸样品,离心铸造后凝固组织结构的细化,使得机械性能进一步提高,具体表现在抗拉强度相比钢模浇铸样品提升了37.6%,断面延伸率提高了97.9%;断口分析表明,离心铸造后断裂类型转变为韧脆混合断裂,材料塑韧性得到大幅度增强。实验结果表明在再生铝合金熔炼过程中,离心浇铸工艺可明显提高合金性能,有效改善产品质量。

旋转喷吹对压铸铝合金(ADC12)熔体密度当量的影响

研究了旋转喷吹除气工艺中转子转速、气体流量、惰性气体种类和挡板浸入铝液的有效长度对ADC12铝合金熔体密度当量的影响。结果表明,转子转速在0~400 r/min和气体流量在0~20 mL/min时,随着其数值增大,铝液的密度当量越小,除气效果越好;当转子转速和气体流量超高时,造成铝液翻滚重新卷气,除气效果变差。N_(2)和Ar对ADC12铝合金熔体的密度当量无明显影响;挡板烧损超过总长的1/3时,铝液的密度当量增大,除气效果变差。在本实验中,转子转速400~450r/min,氮气流量20~25 mL/min为最佳工艺参数。

Effect of AlCoCrFeNi High-Entropy Alloy on Microstructure and Mechanical Properties of Al-Si-Cu Alloy

High-entropy alloy(HEA),as a class of new alloy materials characterized by high stability,excellent specific strength and corrosion resistance,has attracted much attention in the field of aluminum matrix composites(AMCs).To study the effect on microstructure and mechanical properties of aluminum alloys,AlCoCrFeNi HEA particles reinforced ADC12 composites were fabricated by high energy ultrasonic casting process.Subsequently,the effect of HEAs addition on the microstructure and mechanical properties of ADC12 alloys was investigated.Results show that the added HEA particles are tightly bonded to the aluminum matrix.The Al_(2)Cu phase in the matrix is refined.Meanwhile,the tensile strength and microhardness of the alloys with the addition of HEA particles are significantly improved.The yield strength and ultimate tensile strength of as-prepared composites with 12wt%HEAs are increased by 16.9%and 21.9%compared with those of the matrix,respectively.The wear rate of the composites is also decreased due to the enhancement of microhardness under applied load of 20 N.It is mainly attributed to the load transfer strengthening,dislocation proliferation and the optimization of the microstructure.

Y对ADC12合金铸态组织与性能的影响

利用光学显微镜、扫描电子显微镜和X射线衍射仪分析了铸态ADC12-xY（x=0-1.90）合金的组织和相组成,并测试了其流动性能和拉伸力学性能。结果表明,添加Y可显著细化ADC12合金的铸态组织,不仅使初生α-Al由粗大树枝晶转变为细小胞状晶和等轴晶,而且使针状共晶硅转变为细小纤维状或颗粒状,分布更均匀,等轴晶和颗粒状的共晶硅数目大大增加,同时生成针状Al3Y新相。随着Y含量的增加,合金的铸态流动性能和拉伸力学性能均先提高后降低。当Y含量为0.85%时,合金综合性能最佳：流动长度为1541 mm,室温抗拉强度和伸长率分别达到225 MPa和3.5%,较ADC12合金分别提高20%、20%和133%,同时具有优异的高温拉伸力学性能。加入Y后,室温拉伸断口中的解理台阶和河流花样明显减少,解理台阶尺寸亦明显减小,而韧窝明显增多且加深。