Influence of Hot Extrusion Temperature on the Microstructure and the Mechanical Properties of (ABOw + WO3p)/Al Hybrid Composites

The (ABOw + WO₃p)/Al hybrid composite was fabricated by squeeze casting and subsequently hot extruded at temperatures that varied from 440°C to 560°C. The microstructures of extruded composites were examined by scanning electron microscopy and transmission electron microscopy techniques. The results show that ABOw aligns along the extrusion direction after the hot extrusion process. The aspect ratio of ABOw in extruded composites is lower than that of as-cast composite. The aspect ratio of ABOw in extruded composites increases with the increase of extrusion temperature. The larger WO₃p particles are broken into smaller particles during the extrusion process. The transmission electron microscopy (TEM) images show that hot deformation leads to high dislocation density at a lower deformation temperature and leads to grain recovery and recrystallization at a higher deformation temperature. The strength of extruded composites increases first and then decreases with the increase of extrusion temperature, and it reaches maximum value at 500°C. The elongation of extruded composites increases with the increase of extrusion temperature.     

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.     

Strengthening effects of rare earths on wrought Mg---Zn---Zr---RE alloys

The strengthening effect of rare earths (REs) on wrought Mg---Zn---Zr---RE alloys has been studied. It has been shown that the RE elements have a pronounced strengthening effect on the Mg alloys. Homogenization of the cast ingots and the quenching-plus-aging treatment of the extruded bars decreased the strength, whereas aging of the extruded bars increased the strength. It is proposed that the strengthening mechanism is due to RE-containing particles that are able to suppress the dynamic recrystallization during the hot extrusion process, and to promote the dispersive strengthening effect of RE-containing particles in these materials.     

Microstructure development and thixoextrusion of magnesium alloy prepared by repetitive upsetting-extrusion

Thixoextrusion involves processing alloys with a spheroidal microstructure in the semi-solid state. Before thixoextrusion, repetitive upsetting-extrusion (RUE) is introduced into the strain induced metal activation (SIMA) process to predeform AZ80 magnesium alloy. Microstructure evolution of RUE formed AZ80 magnesium alloy during partial remelting is studied at temperatures for times. Tensile mechanical properties of thixoextruded components are determined and compared with those of AZ80 magnesium alloy thixoextruded from starting material produced by casting. The results show that with increasing number of RUE passes solid grain size decreases and the rate of liquation is improved. Prolonged holding time results in grain coarsening and the improvement of degree of spheroidization. The variation of the solid grains with holding time obeys the Lifshitz, Slyozov and Wagner law. Increasing the heating temperature is favorable for the formation of spheroidal solid grains. The tensile properties for AZ80 magnesium alloy thixoextruded from starting material produced by RUE are better than those of AZ80 magnesium alloy thixoextruded from starting material produced by casting.     

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。     

喷射成形Zn—27Al—1Cu合金制备滑动轴承

研究了喷射成形Zn-27Al-1Cu合金棒坯的制备技术、热挤压工艺以及Zn-27Al-1Cu合金滑动轴承的制备技术,分析了喷射成形Zn-27Al-1Cu合金的显微组织、力学性能、耐磨性能。实验结果表明：采用喷射成形制备的Zn-27Al-1Cu合金的棒坯经后续热挤压成形后,具有比传统铸造ZA27合金更高的力学性能和耐磨性能。这种由喷成形Zn-27AL-1Cu合金制造的滑动轴承在实际使用过程中,其寿命比传统材料制造的滑动轴承提高150％以上。     

铝合金拉杆的热挤压工艺及模具设计

分析了高压开关零件LW8-35SF6铝合金拉杆的热挤压成形工艺及模具设计.与传统的加工工艺相比,新工艺采用杆部反挤头部正挤的复合热挤压工艺进行生产,使材料利用率和生产效率大大提高.对铝合金拉杆零件进行了实际生产试验,结果表明,对直径为90 mm、高度为85 mm的棒料进行热挤压成形是可行的,设计制造的挤压模具结构简单、通用性强.采用新工艺增加了坯料尺寸精度,坯料重量减轻72%以上,提高了经济效益;同时,为在小设备上成形变形程度较大的长杆件提供了一种新方法.     

Application of mashy state extrusion

Mashy state extrusion, a new metal forming process, is proposed and investigated. In the process, mashy billets, including solid and liquid components, are extruded into bars, wires, and tubes. The process is applied not only to aluminum alloys and copper alloys, but also to metal-ceramic composites. Through the study, the extrusion conditions necessary to manufacture sound products and mechanical properties of extruded bars, wires, and tubes are investigated. It is found that the extrusion force or pressure for mashy state extrusion is distinctively lower than that for the conventional hot extrusion; therefore, a high extrusion ratio is easily attainable. The mechanical properties of products and their internal structures are satisfactory when the appropriate solid fraction of billet, reduction in area, and cooling conditions at die are employed. Through the investigation, it becomes clear that mashy state extrusion is a metal forming process with very good potential and is effective to manufacture various metal-metal and metal-ceramic composite products.     

AZ31镁合金的热挤压组织与力学性能分析

对常用变形镁合金AZ31进行了热挤压试验,制备出了四种规格的挤压材;观察了挤压前后镁合金的组织变化,并对挤压板材、棒材的力学性能进行了测试。研究结果表明:经过热挤压后,镁合金的晶粒得以细化,同时力学性能得到较大的提高,屈服强度达到200 N/mm2-270 N/mm2,抗拉强度达到300 N/mm2,伸长率在18%左右。     

热挤压变形对搅拌铸造SiCp/2024复合材料显微组织与力学性能的影响

利用搅拌铸造?热挤压工艺制备SiCp/2024复合材料板材。通过金相观察(OM)、扫描电镜(SEM)及力学性能测试等手段研究了该复合材料热挤压变形前后的显微组织与力学性能。结果表明,复合材料铸坯主要由大小为80μm~100μm的等轴晶组成,晶界第二相粗大呈非连续状分布,SiC颗粒较均匀地分布于基体合金,大部分SiC颗粒沿晶界分布,少数颗粒分布于晶内;热挤压变形后,显微孔洞等铸造缺陷和SiC颗粒团聚现象明显消除,SiC颗粒及破碎的第二相沿热挤压方向呈流线分布,复合材料的强度和塑性显著提高;拉伸断口表明,热挤压变形有利于改善SiC颗粒与基体合金的界面结合;SiCp/2024复合材料主要的断裂方式为SiC颗粒断裂和SiC/Al的界面脱粘。     

快速凝固+热挤压制备Al-10.7Zn-2.4Mg-0.9Cu合金的组织和性能

采用单辊熔体旋转法制备Al-10.7Zn-2.4Mg-0.9Cu合金带材,利用热挤压将带材坯料制成棒材,对其微观组织和力学性能进行研究。结果表明:所制备的带材由过饱和固溶体α(Al)等轴细晶构成,晶粒尺寸为3~5μm;合金经挤压后存在粗大第二相,析出相主要为MgZn2相,挤压态棒材抗拉强度为499.8 MPa,伸长率达到了15.3%,断口呈韧性断裂特征;经T6热处理后,合金中有细小的沉淀相析出,使得室温力学性能得到提高,抗拉强度达到631.9 MPa,伸长率有所降低,断口呈韧脆混合断裂特征。     

Microstructure and properties of AZ80 magnesium alloy prepared by hot extrusion from recycled machined chips

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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.     

石墨烯纳米片增强铝基复合材料的制备与性能

采用高能球磨、放电等离子烧结以及热挤压工艺制备含量为5.0％(体积分数)的石墨烯增强铝基复合材料.分别采用X射线光电子能谱、透射电镜及拉伸试验研究挤压态复合材料的显微组织与力学性能,发现5.0％(体积分数)的石墨烯分散在铝晶界上,并且未与铝基体发生界面反应.最终,挤压态复合材料的屈服强度和抗拉强度高达462 MPa和4...     

FORMING PROCESS OF HOT-EXTRUDED SiCw/6061Al COMPOSITES(Ⅰ)

１ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｒｅｃｅｎｔｙｅａｒｓ，ｍｏｒｅａｎｄｍｏｒｅｃｏｎｔｉｎｕｏｕｓｌｙｏｒｄｉｓｃｏｎｔｉｎｕｏｕｓｌｙｒｅｉｎｆｏｒｃｅｄｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ（ＭＭＣｓ）ｈａｖｅｂｅｅｎｕｓｅｄｔｏｍａｋｅｓｔ...     

坯料细化处理对AZ31镁合金挤压组织的影响

对超声细化和未细化的AZ31镁合金棒料进行均匀化退火后热挤压,并对热挤压后的组织和硬度进行了对比分析。结果表明,与未经过晶粒细化处理棒料的热挤压组织相比,预先经过晶粒细化处理的AZ31镁合金棒热挤压组织更加均匀。当挤压比λ为16、挤压料温度为380℃、挤压速度为0.9 m/min时,组织发生回复再结晶。与未经晶粒细化处理棒料的挤压组织相比,经过晶粒细化处理的挤压组织更加细小;挤压速度增加到10 m/min时,经过晶粒细化处理后的AZ31镁合金挤压变形后棒料边缘容易发生二次再结晶现象,形成一条宽约75μm的粗晶组织,边缘附近区域组织中有孪晶形成。同时,经过晶粒细化处理后的AZ31镁合金挤压棒的硬度较高。     

Forming of magnesium alloys at 100 °C by hydrostatic extrusion

Magnesium wrought alloys are of special interest for use as structural parts due to the possibility of obtaining improved and more homogeneous microstructure and mechanical properties compared with cast components. The market for magnesium wrought alloys is still relatively small, and they are only used for special applications due to the high cost of the feedstock. Currently, with the decreasing prices for the primary magnesium extrusion, magnesium has become competitive with aluminum, and is important for upcoming research and development activities. In this study hydrostatic extrusion, as a quite rarely applied technique, was used for deformation of commercial magnesium alloys at 100 °C, which is significantly below the temperature necessary for activation of new gliding systems. All experiments were carried out using typical industrial extrusion parameters like extrusion rate and extrusion ratio but with the objective of obtaining extremely fine-grained materials as are received typically from equal channel angular extrusion processing. These experiments show that the processing of magnesium alloys is possible even at a temperature of 100 °C. The limitations of this processing and the influence of process parameters on the microstructure and mechanical properties of extruded profiles will be discussed.     

The effect of die shape on the hot extrudability and mechanical properties of 6061 Al/Al2O3 composites

Metal matrix composites (MMCs) fabricated by the compocasting process show a homogeneous distribution of the reinforcing fiber in the matrix. Microstructural observation of hot extruded MMCs reveals that as the extrusion ratio increases, the fiber alignment becomes improved, but fiber fracture occurs more severely.The mechanical properties of hot extruded MMCs are better than those of the matrix metal, with the exception of the elongation at failure, and are not influenced significantly by the extrusion temperature. The tensile strength and hardness of MMCs are improved to a greater degree by hot extrusion using a constant-strain-rate die. Also, there exists a critical extrusion ratio that gives maximum strength, which is 5.44 in this study. Additionally, fractograph of the tensile specimen of extruded MMC indicates the ductile fracture behavior of the matrix.     

Mechanical Properties of Al/BN Nanocomposites Fabricated by Planetary Ball Milling and Conventional Hot Extrusion

In this study, Al matrix nanocomposites containing 1, 2 and 4 wt% nano-boron nitride were fabricated by mechanical milling and hot extrusion. The mechanical properties of all extruded samples were evaluated. Also, the morphology and microstructure of the milled composite powders were characterized using two types of electron microscope. The results showed that a high fraction of the boron nitride nanoparticles dissolved and formed a solid solution in Al matrix during the milling process. Through the process of solid solution formation, the work hardening rate of the composite powders increased. This led to a morphological change in the composite powders and resulted in equiaxed shape. The powder particle size also decreased after the milling process. By increasing boron nitride content within a range of 0–4 wt% in the hot extruded samples, tensile stress increased from 212 to 333 MPa. The hardness of the nanocomposite samples including 1, 2 and 4 wt% boron nitride improved approximately 55, 70 and 90% in comparison with pure Al,respectively.     

Fabrication and characteristics of magnesium alloys produced via powder metallurgy

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