喷射成形Al-Fe-V-Si系耐热铝合金的制备工艺和性能

采用喷射成形方法制备了不同成分的Al-Fe-V-Si耐热铝合金，对喷射成形工艺参数进行了优化，对沉积坯件的热挤压工艺进行了探索，对材料的组织进行了分析，并对不同成分材料的性能进行了比较。结果表明：当喷射成形工艺参数选择合理时，沉积坯件具有良好的成形性与致密度，在随后的热挤压过程中，通过较低的挤压比即可使材料达到全致密；沉积坯件热挤压温度的降低有利于使材料获得更高的力学性能；同时，通过对合金成分的优化，可以获得加工和使用性能更加优良的Al-Fe-V-Si耐热铝合金。     

Effect of hot extrusion process on microstructure and mechanical properties of hypereutectic Al-Si alloys

The hypereutectic Al-Si alloy was fabricated by hot extrusion process after solidified under electromagnetic stirring,and the microstructure and mechanical properties of the alloy were studied.The results show that the ultimate tensile strength and elongation of the alloy reached 229.5 MPa and 4.6%,respectively with the extrusion ratio of 10,and 263.2 MPa and 5.4%,respectively with extrusion ratio of 20.This indicates that the mechanical properties of the alloy are obviously improved with the increase of extrusion ratio.After hot extruded,the primary Si,eutectic Si,Mg2Si,AlNi,Al7Cu4Ni and Al-Si-Mn-Fe-Cr-Mo phases are refined to different extent,and the efficiency of refinement is obvious more and more with the increase of extrusion ratio.After T6 heat treatment,the sharp corners of these phases become passivated and roundish,and the mechanical properties are improved.The ultimate tensile strength of the extruded alloy after T6 heat treatment reaches 335.3 MPa with extrusion ratio of 10 and 353.6 MPa with extrusion ratio of 20.     

Properties and microstructures of 7075/SiC_p composites prepared by spray deposition

1　INTRODUCTION70 75aluminumalloyisakindofsuperiorhighstrengthandtoughnessmaterialusedwidelyinsuchfieldsastheframeandpinoftheairplanes ,etc .Withtheapplicationofsuchrapidsolidificationassprayde positionandeffectiveheattreatmenttechnologies ,themechanicalproperties(σb≥ 70 0MPa ,δ≥ 10 % )ofthe 70 75materialwereimprovedmarkedlyintheear ly 1990s[13] .However ,therearefewattractivere sultsreportedaboutthecompositesof 70 75alloy ,es peciallythosepreparedbyspraydepositiontechnolo gy .Toobtai…     

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A EXTRUDED RAPIDLY SOLIDIFIED AIFeVSi ALLOY

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Some studies on hot extrusion of rapidly solidified Mg alloys

Rapidly solidified magnesium alloys show great potential for application in automotive and aerospace industries. In this study, Mg-Al-Zn alloys (AZ91) were rapidly solidified by a melt-spinning process to form ribbons. Pulverized ribbons were cold-compacted and then hot-extruded to form rods. During extrusion, a specially designed die with constant strain rate profile was used and found to be advantageous. By properly establishing the complete process, extruded rods of rapidly solidified AZ91 alloys exhibiting good combination of room temperature strength and ductility were produced. Microstructural investigations were carried out on melt-spun ribbons and extruded rods. Effects of extrusion die shape, extrusion ratio, and extrusion temperature on mechanical properties of the extruded rods were also investigated.     

亚微晶2024铝合金的制备及组织性能研究

将快速凝固２０２４铝合金粉末进行机械球磨，并分别将球磨后的粉末与原始的快速凝固粉末经真空热压制坯及热静液挤压成形。采用透射电镜观察了挤压态及时效状态的微晶２０２４铝合金的组织结构并进行了性能测试。研究结果表明，经过机械球磨后，２０２４铝合金的强度明显提高，并随着球磨时间的增加而增高，延伸率保持在原有水平上，微晶２０２４铝合金的强化机制可能是细晶强化及沉淀强化。此外，由于晶粒细小而导致晶内位错极少，造成明显的拉伸屈服现象，同时材料的加工硬化率降低。     

热挤压工艺对AZ31镁合金组织与力学性能的影响

在不同挤压条件下对AZ31镁合金进行了热挤压试验,并对挤压前后材料组织与力学性能的变化进行了分析.研究结果表明,AZ31镁合金热挤压时发生了动态再结晶,材料组织比铸态时细化,力学性能大幅度提高;AZ31镁合金挤压后的组织及力学性能受挤压温度及冷却方式影响,在本试验范围内,AZ31镁合金在623 K挤压后空冷得到的组织均匀细小,力学性能良好.     

Corrosion and mechanical properties of hot-extruded AZ31 magnesium alloys

AZ31 magnesium alloys were hot-extruded at 573 K and 623 K with extrusion ratio(λ) of 20,35 and 50.The corrosion and mechanical behavior of hot-extruded AZ31 were studied by galvanic tests and tensile tests.The microstructures of the studied AZ31 alloys were also investigated with optical microscope.The results show that,compared with the as-cast AZ31 alloy,the corrosion potentials of all hot-extruded AZ31 alloys are increased by 60 mV.Moreover,at the extrusion temperature of 623 K,the galvanic current o...     

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AZ91D EXTRUDED TUBE

The effect of extrusion ratio on microstruetures and mechanical properties of magnesium alloy AZ91D extruded tube at 430℃ has been studied. After the evolution of microstracture and mechanical properties of AZ91D during extrusion were studied, the following parameters were obtained： tensile strength reached the climax value of 306.9MPa and elongation peak value of 10.1% at an extrusion ratio of 7.125, and with the increase of the extrusion ratio to 7.45, yield strength reached a top value of 285.795MPa with decreased tensile strength and elongation. It was concluded that mechanical properties of magnesium alloys AZ91D could be enhanced by adjusting the extrusion ratio near recrystallization.     

An investigation on the hot extrusion process of magnesium alloy sheet

This study investigates the hot extrusion of magnesium alloy sheets at various temperatures, material, speed and lubricant. A multi-speed method is applied to extrude a magnesium alloy sheet at a high extrusion ratio. The experimental results are analyzed to optimize the processing conditions, increase the tensile strength and reduce the extrusion load on the magnesium alloy thin sheet. Nowadays, most magnesium alloy products are manufactured by industrial die casting. Hot extrusion is seldom used to finish magnesium products because the extrusion speed, temperature and extrusion load significantly effect the properties of the product. In this study, the Taguchi experimental method with the orthogonal array is applied. ANOVA is used to investigate how parameters affect the extrusion process. All possible mechanical properties of the product are analyzed to obtain the optimal process parameters. In addition, magnesium alloys with different compositions are experimentally tested to determine the mechanical properties of the extruded product and obtain the relationship between the process parameters and the properties of the material.     

Effect of heat treatment on tensile and fatigue deformation behavior of extruded Al-12 wt%Si alloy

This study investigated the effect of heat treatment on tensile and high-cycle fatigue deformation behavior of extruded Al-12 wt%Si alloy. The material used in this study was extruded at a ratio of 17.7: 1 through extrusion process. To identify the effects of heat treatment, T6 heat treatment (515 °C/1 h, water quenching, and then 175 °C/10 h) was performed. Microstructural observation identified Si phases aligned in the extrusion direction in both extruded alloy (F) and heat treated alloy (T6). The average grain size of F alloy was 8.15 °C, and that of T6 alloy was 8.22 °C. Both alloys were composed of Al matrix, Si, Al₂Cu, Al₃Ni and AlFeSi phases. As T6 heat treatment was applied, Al₂Cu phases became more finely and evenly distributed. Tensile results confirmed that yield strength increased from 119.0 MPa to 329.0 MPa, ultimate tensile strength increased from 226.8 MPa to 391.4 MPa, and the elongation decreased from 16.1% to 5.0% as T6 heat treatment was applied. High-cycle fatigue results represented F alloy’s fatigue limit as 185 MPa and T6 alloy’s fatigue limit as 275 MPa, indicating that high-cycle fatigue properties increased significantly as heat treatment was conducted. Through tensile and fatigue fracture surface analysis, this study considered the deformation behaviors of extruded and heat treated Al-Si alloys in relation to their microstructures.     

初始组织对热挤压Mg-6Al-2Ca-2Sm合金显微组织和力学性能的影响

对铸态Mg-6Al-2Ca-2Sm合金分别进行经固溶和固溶+时效处理获得不同初始组织试样,然后对不同初始组织的试样进行热挤压,研究了不同初始组织对热挤压Mg-6Al-2Ca-2Sm合金显微组织和力学性能的影响。结果表明：铸态合金经热挤压后发生明显的部分再结晶,显微组织得到显著细化;经固溶或固溶+时效处理能够改善合金组织,热挤压后合金显微组织分布更加均匀。初始组织分布能够改善热挤压Mg-6Al-2Ca-2Sm合金室温和高温力学性能,固溶+时效后进行热挤压,Mg-6Al-2Ca-2Sm合金具有最高的抗拉强度和延伸率。     

喷射沉积高Si铝合金热挤压工艺的研究现状

综述了挤压温度、挤压比对喷射沉积高Si铝合金微观组织和力学性能的影响。比较了不同合金成分的高Si铝合金的力学性能。     

喷射沉积Al—Si—Fe—Cu—Mg合金的微观组织和力学行为

对喷射沉积技术制备的Ａｌ－Ｓｉ－Ｆｅ－Ｃｕ－Ｍｇ合金沉积态、挤压态及挤压后热处理的微观组织进行了观察和分析，并对合金在后两种状态下的室温和高温拉伸性能进行了测试，提出了合金的强化和断裂机制。     

Validation of a systematic approach to modeling spray quenching of aluminum alloy extrusions, composites, and continuous castings

Optimal cooling of aluminum alloys following the high- temperature extrusion process suppresses precipitation of intermetallic compounds and results in a part capable of possessing maximum strength and hardness after the subsequent age- hardening process. Rapid quenching suppresses precipitation but can lead to large spatial temperature gradients in complex- shaped parts, causing distortion, cracking, high residual stress, and/or nonuniform mechanical properties. Conversely, slow cooling significantly reduces or eliminates these undesirable conditions but allows considerable precipitation, resulting in low strength, soft spots, and/or low corrosion resistance. This study presents a systematic method of locating and operating multiple spray nozzles for any shaped extrusion such that uniform, rapid cooling and superior mechanical and metallurgical properties are achieved. A spray nozzle data base was compiled by measuring the distribution of spray hydrodynamic parameters (volumetric spray flux, mean drop diameter, and mean drop velocity) throughout the spray field of various industrial nozzles. Spray heat transfer correlations, which link the local spray hydrodynamic parameters to the heat transfer rate in each of the boiling regimes experienced by the surface, defined the spatially nonuniform boundary conditions in a numerical model of the quenching process that also accounted for interference between adjacent spray fields. New correlations, offering increased accuracy and less computational time, were formulated for the high- temperature boiling regimes which have a critical influence on final mechanical properties. The quench factor technique related predicted thermal history to metallurgical transformations occurring within the extrusion to predict hardness distribution. The validity of this unique approach was demonstrated by comparing model predictions to the temperature response (and hardness after artificial aging) of an L- shaped Al 2024- T6 extrusion to quenches with multiple, overlapping water sprays. The validation study reported herein concludes by exploring the possibility of applying quenching technology to improving the properties of extruded metal- matrix composites such as SiC_p/Al 6061 and cast alloys.     

高强塑性TiB2P/Al复合材料的制备与力学性能

采用TiB2颗粒与铝粉混配的方法,获得利于成形的预制体,采用压力浸渗法制备体积分数为20%的TiB2P/6061Al复合材料,并采用10:1的挤压比对复合材料进行热挤压。利用扫描电镜(SEM)、透射电镜(TEM)和万能电子拉伸机对热挤压前后复合材料的微观组织及力学性能进行研究,发现经过该种方法制备的复合材料经热挤压后具有良好的室温拉伸力学性能,抗拉强度为447.5MPa,弹性模量为121.8GPa,延伸率可达7.95%,显示出良好的强塑性配合,分析其强塑性来源于增强体与基体之间的良好界面结合、晶粒细化强化和沉淀强化。     

双向双通道变通径挤压AZ31镁合金的显微组织及变形行为

在不同温度下,采用双向双通道变通径挤压(DDE)对AZ31镁合金进行挤压,研究该工艺对其组织、力学性能、拉压不对称性和断裂行为的影响。结果表明:与均匀态AZ31镁合金相比,挤压后所得试样的晶粒显著细化,力学性能和拉压不对称性得到改善;与采用等通道角挤压工艺多道次挤压试样的力学性能相比,该工艺具有一定的优势。此外,随着挤压温度的升高,晶粒尺寸逐渐增大,显微硬度、抗拉强度和压缩率逐渐降低。从250℃到450℃,晶粒尺寸从6μm增大到26μm,硬度值(HV)从67降低到56,抗压强度从400MPa降低到343MPa,压缩率从14.8%降低到9.7%。均匀态AZ31和挤压态AZ31的压缩断口均为穿晶断裂,前者断裂机理为脆性解理断裂,后者为韧脆结合型准解理断裂。     

Squeeze casting of aluminium alloys for higher formability in cold forging

Abstract

This research project investigated the process conditions of using squeeze casting process to produce aluminium alloy preforms or billets for subsequent cold forging process. The comparative effects of heat treatments, their microstructures and mechanical properties were evaluated. Through these studies and experiments, the main emphasis is on the study of commercial material Al 6061, Al 2014 and Al 356 alloys. The formability of the alloys was carried out using forward and backward extrusion test at 50% area reduction at room temperature (cold extrusion). It was found that when wrought aluminium 6061, 2014 and 356 alloys were squeeze cast to form the preforms, the preform microstructures revealed very fine microstructures that are feasible to be cold extruded. In addition, after thermal annealing treatment of 6061 squeeze cast preforms, the samples showed a similar value of work hardening exponent value of 0˙20 as compared to the wrought aluminium alloy 6061, with a workhardening exponent value of 0˙21 obtained from the static compression test. Wrought aluminium alloys generally cost twice the amount as compared with casting ingots. The microstructures of the squeeze cast 6061 alloy showed no visible cracks or inclusions after the deformation by extrusion. The results of the studies showed that Al 6061 preforms via squeeze cast technique may be cold extruded or formed, which provide an alternative means for the production of billets for the cold extrusion or forging process.     

Microstructures and mechanical properties of the extruded Mg-4Y-2Gd-xZn-0.4Zr alloys

Microstructures and mechanical properties of the Mg-4Y-2Gd-0.4Zr alloy with Zn additions have been investigated. The investigation suggests that the mechanical properties of the alloys have been greatly improved after hot extrusion due to the refinement of microstructures, especially the elongations. The extruded Mg-4Y-2Gd-1.0Zn-0.4Zr alloy displays excellent tensile properties. The ultimate tensile strength and the yield tensile strength are 291 and 228 MPa, respectively, with an elongation of 28%. The additions of Zn have an obvious effect on refining microstructure of the extruded alloys, and the vicker hardness increases with increasing Zn additions. The age hardening responses of the extruded alloys have been investigated at 220 °C. These alloys display unobvious ageing hardness responses.     

Water-Air Spray Cooling of Extruded Profiles: Process Integrated Heat Treatment of the Alloy EN AW-6082

Quenching by spray cooling in the press line is a promising way to harden Al-Mg-Si alloys with regard to reducing profile distortion. For alloys such as EN AW-6082, high cooling rates are required. A device for spray cooling by means of water and compressed air was integrated into a 10 MN horizontal, hydraulic, short-stroke extrusion press. Various spray parameters were investigated. By using 32 water-air nozzles having a total water deposition rate of about 15 L/min and extruding with a profile velocity of 2.5 m/min, high mechanical properties were imparted to 30 mm diameter extruded rods. This arrangement ensures the extruded alloy is cooled to almost room temperature. Comparable properties can be achieved by water quenching, although the water consumption will be tenfold higher. The distribution of water deposition density on the profiles’ surfaces was determined. It was shown that an adjustment of the water-air pressure ratio allows the final temperature of the profiles to be controlled over a wide range. Minimization of temperature gradients in the cross section of complex profiles allows profile distortions to be reduced.