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.     

连续挤压机用新型堵头模具材料的研制

在K403合金基础上通过铸锻工艺制备出连续挤压机用新型堵头模具材料——GH403合金,然后对GH403合金的组织结构和力学性能进行了观察分析,并在TLJ400型连续挤压机上采用GH403合金堵头进行了应用实验.结果表明:GH403合金组织均匀,具有良好的强韧综合性能,可以满足铜镁合金的连续挤压需要;在连续挤压高强度铜镁合金过程中,其挤压寿命比H13高出17倍,具有良好的性价比.     

Deformation rate response of an Al-Si alloy prepared from rapidly solidified powder

A study on the deformation rate response of an important Al-Si-Cu-Mg alloy prepared from rapidly solidified powder is undertaken, through hot extrusion and tensile tests which cover a wide variation of strain rate. The individual effects of ram speed in extrusion and crosshead speed in tensile tests on the flow behavior of the material are analyzed. It is derived that the pressure requirement for extrusion is a combined function of ram speed (or strain rate) and temperature rise. The balance of the two factors gives an increase in extrusion pressure with rising ram speed—a result being different from that found in the extrusion of some other aluminum alloys. The tensile results obtained from the extruded material, using constant and incremental strain rate methods, prove that the flow stress of the alloy under study is more sensitive to strain rate than that of other aluminum alloys. Finally, a direct comparison between the two deformation processes is made in terms of the flow stress dependence of strain rate.     

Extrusion of an aluminum alloy prepared from rapidly solidified powder

A study on powder extrusion is attempted to extend the understanding of the extrusion process and the interrelationship between process variables and forces involved. The extrusion characteristics of a promising Al-Si alloy produced from rapidly solidified powder, and the effects of such variables as temperature, reduction ratio, and die geometry on extrusion pressure and friction force have been investigated. Results show that extrusion starts prior to the attainment of a peak pressure. The friction force between the billet and lubricated container occupies only about 4.5% of the peak pressure. This friction is therefore not principally responsible for the pressure drop of about 50% from a peak value to a steady state occurring during extrusion—a finding which is in conflict with the traditional understanding of extrusion. It is also found that temperature-compensated strain rate Z can satisfactorily reflect the combined effects of the process variables on the pressure requirement. The relationship between the Z parameter and the pressure required for the extrusion of the powdered metal (PM) alloy has been formulated, and thus together with the consideration of press capacity and product quality, the extrusion process can be well controlled.     

Fabrication and mechanical properties of high-performance aluminum alloy

High-performance Al–Cu–Mg alloy was fabricated by high-energy ball milling, sintering, and hot extrusion. The microstructure and mechanical properties of the material were preliminarily investigated. Results show that the formation of liquid phase during sintering promotes the densification of the aluminum powders. A97.1 % theoretical density is achieved in this alloy after sintering. The material shows excellent mechanical properties after extrusion and heat treatment. The ultimate tensile strength and yield strength of the extruded samples with heat treatment are 613 and 465 MPa, respectively.     

An upper-bound solution for axisymmetric extrusion of composite rods through curved dies

The study is concerned with an analysis of forward extrusion of composite rods through curved dies. A kinematically admissible velocity field is derived by assuming proper streamlines and applying the flow function concept to each material region of plastic deformation. Two kinds of flow functions are chosen in order to compare the effect of the choice of the flow functions. The effect of work-hardening is incorporated approximately by calculating the strains at the exit of both materials. The upper-bound method is then employed to determine the extrusion pressure for various process variables. The experiments are carried out with commercially pure aluminum and copper billets for various reductions of area and cone angles at room temperature. The experimental results are then compared with the theoretical calculations. The comparison shows that the second-order flow function is in better agreement with the experimental observation both in extrusion loads and in deforming regions.     

机械合金化制备高熵合金研究进展

高熵合金作为一种新型合金逐渐被人们所关注,机械合金化是一种制备先进材料的固态加工工艺,利用机械合金化制备高熵合金也为高熵合金的发展及应用开拓了广阔的领域。本文介绍了高熵合金的简单概念,并从机械合金化中的元素选择、高熵合金粉末的后处理工艺及机械合金化制备高熵合金的研究方向三个方面综述了其研究进展。     

时效处理对镁合金组织和力学性能的影响

在Mg-12.55Al-3.33Zn镁合金中添加少量Ca和Nd元素,利用喷射沉积和热挤压技术制备了改型的Mg-Al -Zn镁合金.采用光学显微镜、X射线衍射、硬度试验、扫描电镜及拉伸试验等研究了合金的微观组织和力学性能.结果表明,T6态和热挤压态合金的组织均较细小致密,相组成也相同.但T6态合金的力学性能略低于热挤压态...     

Material flow and microstructure in the friction stir butt welds of the same and dissimilar aluminum alloys

The material flow and microstructural evolution in the friction stir welds of a 6061-Al alloy to itself and of a 6061-Al alloy to 2024-Al alloy plates of 12.7 mm in thickness were studied under different welding conditions. The results showed that plastic deformation, flow, and mechanical mixing of the material exhibit distinct asymmetry characteristics at both sides of the same and dissimilar welds. The microstructure in dissimilar 6061-Al/2024-Al welds is significantly different from that in the welds of a 6061-Al alloy to itself. Vortex-like structures featured by the concentric flow lines for a weld of 6061-Al alloy to itself, and alternative lamellae with different alloy constituents for a weld of 6061-Al to 2024-Al alloy, are attributed to the stirring action of the threaded tool, in situ extrusion, and traverse motion along the welding direction. The mutual mixing in the dissimilar metal welds is intimate and far from complete. However, the bonding between the two Al-alloys is clearly complete. Three different regions in the nugget zone of dissimilar 6061-Al/2024-Al welds are classified by the mechanically mixed region (MMR) characterized by the relatively dispersed particles of different alloy constituents, the stirring-induced plastic flow region (SPFR) consisting of alternative vortex-like lamellae of the two Al-alloys, and the unmixed region (UMR) consisting of fine equiaxed grains of the 6061-Al alloy. Within all of these three regions, the material is able to withstand a very high degree of plastic deformation due to the presence of dynamic recovery or recrystallization of the microstructure. The degree of material mixing, the thickness of the deformed Al-alloy lamellae, and the material flow patterns depend on the related positions in the nugget zone and the processing parameters. Distinct fluctuations of hardness are found to correspond to the microstructural changes throughout the nugget zone of dissimilar welds.     

2A70铝合金挤压型材生产工艺研究

介绍了2A70铝合金挤压裂型材生产工艺的研究情况。论述了2A70铝合金成分的控制范围、配料要求、熔铸工艺和挤压模具设计制造及修理技术，铸棒的均匀退火加热制度，挤压温度－速度、淬火、时效工艺参数的制定。通过对不同成分的2A70铝合金成分进行熔铸试验，在不同工艺制度下对2A70铝合金铸棒进行挤压试验，对2A70铝合金挤压型材进行不同工艺制度下的时效处理，最终研究出用于我厂生产的工艺制度。结果表明，采用此种工艺制度生产出了材料强度高、耐热性能好，用于生产现场后取得理想的效果。     

沙漏挤压镦粗复合加工技术

本文研究了一种新的晶粒细化方法 :沙漏挤压工艺。这种工艺是在一定温度下通过对材料进行反复挤压产生大的塑性变形 ,同时进行动态再结晶而使材料得到细化。本文对铸态 Zn- Al合金进行了实验 ,初步研究了沙漏挤压工艺对于材料组织和性能的影响。实验结果表明 :沙漏挤压工艺能够有效的细化晶粒 ,使材料获得均匀的等轴细晶组织和优良的综合性能 ,并有助于实现高应变速率超塑性     

Shear banding phenomenon during severe plastic deformation of an AZ31 magnesium alloy

Severe plastic deformation was applied on a wrought AZ31 magnesium alloy by a new method called accumulative back extrusion (ABE). Instabilities of plastic flow in the form of localized shear bands were experimentally observed during ABE processing of the AZ31 alloy. The obtained microstructures show the appearance of shear bands in ABE processed specimens, the extent of which was observed to be decreased by increasing the temperature. The restricted flow (due to the deformation geometry) was discussed as the main cause of the latter behavior. A noticeable grain refinement was observed inside the shear bands which was attributed to the occurrence of continuous dynamic recrystallization inside the bands. To analyze the homogeneity of mechanical properties, the microhardness variations from the deformed bulk to the shear bands were measured and interpreted. The role of shear banding in grain refinement with no harmful effect on material soundness was explained.     

5456铝合金挤压型材生产工艺研究

5456铝合金是在A l-Mg系合金基础上,添加适量的Mn、Cr、Ti和Be元素,并严格控制Fe+S i杂质含量而发展的一种新的铝合金,它类似于5A05铝合金。通过试验,研究合金成分、挤压温度、挤压系数、拉伸率等因素对5456铝合金挤压型材组织和性能的影响规律,确定出该合金合理的挤压生产工艺参数,生产出了满足用户要求性能的产品。     

工艺参数对静液挤压2024铝合金纳米晶组织性能的影响

实验研究了以快速凝固和机械合金化复合工艺制备的２０２４ 铝合金纳米晶粉末为原料, 采用热静液挤压工艺在不同挤压工艺条件下固结成形的挤压态材料的显微组织与力学性能, 探讨了作为主要工艺参数的挤压温度和挤压比对材料组织性能的影响规律及其原因。在此基础上, 进一步确定了２０２４ 铝合金纳米晶粉末热静液挤压固结成形时的挤压温度与挤压比的合理取值范围     

流速对船舶海底阀箱5083-H116铝合金电化学行为的影响

研究流速对铝制船舶的海底阀箱材料5083-H116铝合金电化学行为的影响。为检测电化学特性和流速对其性能的影响,实验在静态和通过搅拌仪产生的4个不同流速下进行,并使用超声波振荡器利用压电效应进行空化实验。结果表明,合金在施加流速后其腐蚀电流密度和损害程度较在静态环境下增加,更易于发生腐蚀。     

Solid-state recycling of aluminium alloy swarf through cold profile extrusion and cold rolling

In this study, the possibility of solid-state recycling of aluminium alloy machining swarf using cold extrusion and a subsequent cold rolling process is investigated. Cast Al-Si alloy swarf was cold compacted into billets and successfully profile-extruded into square bars with a rectangular cross-sectional aspect ratio of 1:1.8 under an extrusion ratio of 4 or more. After annealing, the extruded bars underwent multi-pass cold rolling into 1-mm thick strips with a total rolling reduction of 85%. Optical microscopy demonstrated that in material recycled using only an extrusion process, coarse residual voids existed in regions where insufficient plastic strain was introduced, causing a visible expansion of the material during heat treatment. However, uniaxial tensile tests showed that extrusion-recycled material had a higher mechanical strength than the original aluminium alloy, implying sufficient bonding among the individual pieces of machining swarf. It was also found that the strength and density of material recycled through extrusion and an additional rolling process were superior to material recycled using extrusion only. Moreover, it was observed that the ductility of the recycled materials was inferior to that of the original aluminium alloy.     

快速凝固镁合金挤压棒材及其组织性能研究

双辊快速凝固技术能够细化晶粒、增大合金固溶度,可以大幅度地提高传统结构材料的综合性能。文中以镁合金快速凝固薄片为原料挤压制备了快速凝固棒材,介绍了快速凝固薄片的挤压设备和工艺,分析了快速凝固挤压棒材的微观组织和力学性能。发现在适当的工艺条件下,可以制备出比镁合金铸锭挤压棒材的组织性能更优良的快速凝固镁合金挤压棒材。     

AZ31B变形镁合金压力成形

总结了AZ31B变形镁合金挤压、轧制和热冲压拉深的研究工作。AZ31B挤压板材无裂纹、无烧损,其组织呈晶粒细小的等轴晶;用分流挤压铝合金技术可生产挤压比不大于45,厚度不小于1 5mm的非薄壁镁合金管材;交叉轧制的镁合金薄板的A显著提高,Rp0.2和Rm明显下降;单向轧制时,则出现相反的结果。采用机械冲压法成功地热冲压出60mm×60mm×20mm的方形件,无裂纹现象。     

Extrusion of hybrid sheet metals

This study focused on the extrusion of hybrid sheet metals. Co-extrusion of profiles having sheet metals as reinforcing elements are a promising alternative to the more common rotation-symmetric composite rods or wire reinforced profiles. The influence of non-rotation-symmetric die geometry was investigated by extruding aluminum alloy billets with three different types of sheet metals as core material and the aluminum alloy (AlMgSi1 EN AW-6082) as sleeve material. The hybrid sheet metals were analyzed by non-destructive testing using ultrasonic testing and X-ray inspection. The steel (DC 06) and the titanium (titanium grade 1) cores fractured during extrusion, while the magnesium alloy core (AZ31) showed a uniform deformation. A new deformation mode in co-extrusion has been found for the titanium grade 1 core which most likely fractured due to a combination of tensile and shear stresses caused by the material flow of the non-symmetrical cross-section of the profile. The DC 06 core predominantly fractured due to tensile stresses. Microstructural analysis showed a decrease in thickness for all cores, with AZ31 showing the highest reduction and DC 06 the lowest. It was found that no intermetallic phases occurred having a DC 06 or titanium grade 1 core. However, EDX line scans indicated the start of diffusion processes at the interphase of EN AW-6082 and DC 06. An intermetallic phase could be observed for the specimens having an AZ31 core, EDX line scans showed this to be the Al₃Mg₂ (β) phase.The experimental results state that special constraints have to be taken into consideration, especially concerning material flow of the sleeve material, when extruding hybrid sheet metals with reinforcements of higher strength sheet metal cores.     

固相合成道次对ZM6-Ce镁合金组织和性能的影响

采用固相合成法合成ZM6镁合金废屑和Mg-Ce中间合金屑,研究挤压合成次数对合成镁合金棒组织和性能的影响,并讨论其断裂行为。结果表明:一次挤压后,Mg-Ce中间合金屑没有被破碎,合金的力学性能较差。经5次挤压后,Mg-Ce中间合金屑的均匀分布使合金的力学性能有较大的改善。随着挤压次数的增加,合金的抗拉强度和延伸率增大,增大的幅度随着挤压次数的增加而变小。5次挤压后,合金的抗拉强度为300 MPa,延伸率为14.8%,试样的断裂方式为穿晶韧窝断裂。