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.     

Influence of extrusion parameters on grain size and texture distributions of AZ31 alloy

Grain size and texture distributions have great influences on the mechanical properties of extruded rods. In order to study grain size and texture evolution during the hot extrusion process, direct extrusion tests were carried out with a variety of extrusion parameters (extrusion ratio, temperature and velocity) for commercial as-cast AZ31 magnesium alloys. Extruded specimens were investigated by optical microscopy (OM) and electron backscattered diffraction (EBSD). Experimental results show that extrusion ratio is the most important parameter for grain size refinement. Basal fiber textures with various (0 0 0 2) pole intensities are observed in extruded rods. Maximum intensities increase with the decreasing extrusion ratio and the increasing velocity, while the influence of temperature depends on the value of extrusion ratio and velocity.     

Mg-3Zn-1Y-0.6Zr-0.5Ca生物镁合金不同速度挤压后组织性能研究

采用常规铸造法制备了Mg-3Zn-1Y-0.6Zr-0.5Ca生物镁合金。研究了在不同正挤压速度下(10, 30, 60, 90mm/min)挤出的变形镁合金显微组织和力学性能的影响。研究结果表明:随着挤压速度的增大,动态再结晶晶粒尺寸增大,未动态再结晶区域减少。不同挤压速度影响第二相的形态和分布,进而影响动态再结晶的发生。织构随着挤压速度的增大而减弱。随着挤压速度的增大,合金的塑性增强,抗拉强度减小。在挤压速度为60mm/min 时,综合力学性能良好。抗拉强度270Mpa,伸长率19.6%。     

Development of aluminum rheo-extrusion process using semi-solid slurry at low solid fraction

An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications. However, this process has a high production cost due to the need for investment of high-pressure machinery. The objective of this work is to develop a new semi-solid extrusion process using semi-solid slurry at low solid fractions. A laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 mm. The semi-solid metal process used in this study was the gas induced semi-solid (GISS) technique. To study the feasibility of the GISS extrusion process, the effects of extrusion parameters such as plunger speed and solid fraction on the extrudability, microstructure, and mechanical properties of extruded samples were investigated. The results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produce complete extruded parts.     

Effect of tungsten content on microstructure and quasi-static tensile fracture characteristics of rapidly hot-extruded W-Ni-Fe alloys

Tungsten heavy alloys (WHAs) with three different compositions (90W-7Ni-3Fe, 93W-4.9Ni-2.1Fe and 95W-3.5Ni-1.5Fe, wt.%) were heavily deformed by one-pass rapid hot extrusion at 1100 °C with an extrusion speed of ~ 100 mm/s and an extrusion ratio of ~ 3.33:1. The influence of tungsten content on the microstructure and tensile fracture characteristics of the as-extruded alloys was investigated in detail. The results show that the tungsten particles in the as-extruded 95W have the largest shape factor compared to the as-extruded 90W and 93W alloys and this implies that the tungsten particles in the as-extruded 95W alloy were subjected to the heaviest plastic deformation. In addition, ultimate tensile strength (UTS) and hardness (HRC) are significantly improved after rapid hot extrusion. The as-extruded 95W alloy processes the highest strength (1455 MPa) and hardness (HRC40) but the lowest elongation (5%), followed by the as-extruded 93W (UTS1390MPa; HRC39; 7%) and 90W alloys (UTS1260MPa; HRC36; 10%). The fracture morphology shows the distinct fracture features between the as-sintered alloys and the as-extruded alloys. For the as-sintered alloys, the fracture modes are various while transgranular cleavage of tungsten particles is the main characteristic in the as-extruded alloy. Meanwhile, the fracture modes of the three as-extruded alloys vary slightly with the tungsten content. TEM bright field images indicate that many lath-like subgrains with the width of 150-500 nm are present in the three as-extruded alloys, particularly in the as-extruded 93W and 95W alloys. Furthermore, the dislocations are absent in the γ-(Ni, Fe) phase. This means that dynamic recovery-recrystallization process took place during rapid hot extrusion.     

Microstructure and mechanical properties of Mg–Zn–(Nd)–Zr alloys with different extrusion processes

The effect of Nd addition and the in?uence of extrusion processes on the microstructure and mechanical properties of Mg–6Zn–0.5Zr(ZK60) and Mg–6Zn–1.5Nd–0.5Zr(ZKNd602) alloys were investigated. Nd element can obviously re?ne the microstructure of both as-cast and asextruded Mg–Zn–Nd–Zr alloy. All of the extruded alloys exhibit a bimodal grain structure composed of equiaxed?ne recrystallized(DRXed) grains and elongated coarse un DRXed grains. It is necessary to achieve high strength,particularly the yield strength, for ZKNd602 alloy, when it is extruded with a lower extrusion temperature, a suitable extrusion ratio and a relatively lower extrusion ram speed. In this study, the ultimate tensile strength(UTS),yield strength(YS) and elongation(El) of the extruded ZKNd602 alloy were 421 MPa, 402 MPa and 6.7 %,respectively, with extrusion temperature of 290 °C, extrusion ratio of 18:1 and a ram speed of approximate0.4 mm·s~(-1). Meanwhile, the extrusion process has obvious effects on the room-temperature properties but weak effects on the high-temperature properties.     

Superplastic-like behavior of Al-high Si alloys produced from rapidly solidified powders and ribbons

The high temperature tensile properties of hyper-eutectic Al-Si alloys were studied at temperatures between 683 and 813 K at initial strain rates between 8.3X10⁻⁴ and 4.2X10⁻¹s⁻¹. The alloys were prepared from prealloyed powders and ribbons, which were respectively fabricated by the centrifugal atomization and melt spinning, through the hot extrusion process at an extrusion ratio of 110:1. The extruded alloy bars prepared from the powders and ribbons, i.e. the powder-extruded and ribbon-extruded bars, have homogenous micro-structures with the fine silicon particles dispersed in the aluminum matrices for the Al-25Si and Al-15Si alloys. The maximum elongation-to-failure of the powder-extruded bar and the ribbon-bar are almost equal, 150%, for the Al-25Si alloy, In the Al-15Si alloy, the ribbon-extruded bar has superior elongation compared to the powder-extruded bar, that is, these are respectively 520% and 400%. The maximum elongation was attained at the relatively high strain rate of 10⁻²s⁻¹ independent of the silicon content and solidification process.     

Plastic deformation behavior of Mg97Zn1Y2 extruded alloys

The mechanical properties of the Mg97ZnlY2 extruded alloy containing the long-period stacking ordered phase, the so-called LPSO-phase, with a volume fraction of 24%-25%, were examined by compression tests and cyclic tension-compression deformation tests. The plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2Y0.6 and Mg89Zn4Y7 （molar fraction, %）, which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1Y2 Mg/LPSO two-phase alloy, respectively, were also prepared. By comparing their mechanical properties, the strengthening mechanisms operating in the Mg97Zn1 Y2 extruded alloy were discussed. Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion, which led to a large increment of the strength of alloy. In addition, the LPSO-phases, which were aligned along the extrusion direction in Mg97Zn1Y2 extruded alloy, acted as hardening phases, just like reinforced fibers.     

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

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭａｇｎｅｓｉｕｍａｌｌｏｙｓｈａｖｅｍａｎｙａｄｖａｎｔａｇｅｓｓｕｃｈａｓｌｏｗｄｅｎｓｉｔｙ ,ｈｉｇｈｓｐｅｃｉｆｉｃｓｔｒｅｎｇｔｈ ,ｇｏｏｄｅｌｅｃｔｒｏｍａｇ ｎｅｔｉｃｓｈｉｅｌｄｉｎｇｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ,ｅｘｃｅｌｌｅｎｔｃａｓｔａｂｉｌｉｔｙａｎｄｍａｃｈｉｎａｂｉｌｉｔｙｅｔｃ .Ｍａｇｎｅｓｉｕｍｉｓａｎａｂｕｎｄａｎｔｅｌｅ ｍｅｎｔｓｉｎｃｅａｂｏｕｔ 1.93% (ｍａｓｓｆｒａｃｔｉｏｎ)ｏｆｅａｒｔｈｃｒｕｓｔｃｏｎｓｉｓｔｏｆｍａｇｎｅ…     

热挤压对铸态Mg-1Zn-0.3Zr-1Y-2Sn镁合金组织和性能的影响（英文）

通过光学显微镜(OM)、扫描电镜(SEM)、浸泡实验、析氢实验、电化学试验、拉伸试验等方法,研究了不同挤压温度(340、360、380、400℃)下,热挤压对铸态Mg-1Zn-0.3Zr-1Y-2Sn合金组织和性能的影响。结果表明:热挤压后,合金的第二相沿挤压方向破碎成颗粒,微观组织中存在动态再结晶和变形晶粒。随着挤压温度的升高,第二相的含量变化较小,动态再结晶晶粒尺寸逐渐增大。热挤压后,合金的力学性能得到改善,但其耐腐蚀性最终减弱。热挤压处理可以在腐蚀的早期阶段提高合金的耐腐蚀性能,但随着腐蚀的进行,在后期合金的耐蚀性能会降低。当热挤压温度为360℃时,合金具有较好的力学性能和耐腐蚀性能。     

Microstructure,mechanical properties,and corrosion resistance of Mg–9Li–3Al–1.6Y alloy

Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scanning electronic microscopy(SEM), X-ray diffraction(XRD), mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al_2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.     

Microstructure and Mechanical Properties of AZ31 Mg Alloy Fabricated by Pre-compression and Frustum Shearing Extrusion

The AZ31 Mg alloys were processed by 6% pre-compression and frustum shearing extrusion at various temperatures, and the microstructure, texture and mechanical properties of the resulting alloys are systematically investigated. The results show that the grain size monotonically increases from 6.4 to 12.6 lm and the texture intensity increases from 6.7 to 9.6with the increase in the extrusion temperature. The combining effect of the pre-twinning and the frustum shearing deformation is found to contribute to the development of the weak basal texture in Mg alloys. The Mg alloy sheet produced at the extrusion temperature of 563 K exhibits excellent mechanical properties. The yield strength, ultimate tensile strength and elongation for the extruded alloys are 189.6 MPa, 288.4 MPa and 24.9%, respectively. Such improved mechanical properties are comparable or even superior to those of the alloys subjected to other deformation techniques, rendering the pre-compression and frustum shearing extrusion a promising way for further tailoring properties of Mg alloys.     

Effect of scandium on the hot extrudability of 7075 aluminum alloy

This study investigated the effect of the addition of scandium on the hot extrudability of 7075 alloys. Three kinds of Al-Zn-Mg-(Sc) alloys with up to 0.30 wt.% Sc were prepared, including 7075 aluminum alloy without Sc (AA7075). Differential scanning calorimetry (DSC) analyses and hot compression tests were conducted to examine the incipient melting temperature of the alloys produced. The addition of 0.30 wt.% Sc resulted in significant grain refinement and a fully equiaxed microstructure. Hot compression tests were conducted to determine the critical damage values based on Cockroft-Latham criterion. Then, the surface quality of an extruded bar of each alloy was simulated with a finite element code. The surface condition of an extruded bar was predicted and compared with the experimental results. After hot extrusion, AA7075 without the addition of Sc showed a more moderate surface quality than the alloys modified with Sc. However, AA7075 revealed coarse-grained bands just below the surface area. Extrusion limit diagrams were constructed for the three alloys.     

Effect of Extrusion and Annealing Regimes on Mechanical Properties of Powder Alloys of the Mo – Zr – B System

The effect of extrusion and heat treatment regimes on mechanical properties of rods 40 – 45 mm in diameter fabricated from powder molybdenum alloys is investigated. The alloys are fabricated from a mixture of Mo and 0.1 – 2.0% ZrB₂. A deformed alloy of molybdenum with 2% ZrB₂ is shown to be hardened effectively. An optimum composition is chosen for a high-temperature molybdenum alloy possessing good ductility at 20°C in deformed and recrystallized states.     

Development of new magnesium based alloys and their nanocomposites

In the present study, 1 and 2 wt.% of aluminum were successfully incorporated into magnesium based AZ31 alloy to develop new AZ41 and AZ51 alloys using the technique of disintegrated melt deposition. AZ41-Al₂O₃ and AZ51-Al₂O₃ nanocomposites were also successfully synthesized through the simultaneous addition of aluminum (1 and 2 wt.%, respectively) and 1.5 vol.% nano-sized alumina into AZ31 magnesium following same route. Alloy and composite samples were then subsequently hot extruded at 400 °C and characterized. Microstructural characterization studies revealed equiaxed grain structure, reasonably uniform distribution of particulate and intermetallics in the matrix and minimal porosity. Physical properties characterization revealed that addition of both aluminum and nano-sized alumina reduced the coefficient of thermal expansion of monolithic AZ31. The presence of both Al and nano-sized Al₂O₃ particles also assisted in improving overall mechanical properties including microhardness, engineering and specific tensile strengths, ductility and work of fracture. The results suggest that these alloys and nanocomposites have significant potential in diverse engineering applications when compared to magnesium AZ31 alloy.     

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.     

Effect of processing parameters on microstructures and mechanical properties of rapidly solidified AlFeVSi hot-extruded product

1　INTRODUCTIONRapidlysolidifiedAlFeVSialloy ,developedus ing planarflowcastingbytheAllied SignalAlu minumCompanyofUSA ,isoneofthemostmatureheat resistantaluminumalloysatpresent.FVS0 6 11,FVS0 812andFVS12 12havebeenappliedinthein dustriesofaviationandaerospacetomeettheneedsofadvancedaircraftsforlightweightstructuralmaterialswithhighspecificstrength ,highspecificstiffnessandexcellentthermalstability[14 ] .Theblanksofrapidlysolidifiedheat resistantalu minumalloywereprocessedbyusingpl…     

Characterization of the High-Strength Mg–3Nd–0.5Zn Alloy Prepared by Thermomechanical Processing

Magnesium alloys based on Nd and Zn are promising materials for both aviation industry and medical applications.Superior mechanical properties of these materials can be achieved by thermomechanical processing such as extrusion or rolling and by aging treatment, which can significantly strengthen the alloy. The question remains especially about the connection of texture strength created in the alloys based on the specific conditions of preparation. This work focuses on the Mg–3 Nd–0.5 Zn magnesium alloy prepared by hot extrusion of the as-cast state at two different temperatures combined with heat pre-treatment. Extrusion ratio of 16 and rate of 0.2 mm/s at 350 and 400 °C were selected for material preparation. The structures of prepared materials were studied by scanning electron microscopy and transmission electron microscopy. The effect of microstructure on mechanical properties was evaluated. Obtained results revealed the strong effect of thermal pre-treatment on final microstructure and mechanical properties of extruded materials. The Hall–Petch relation between grain size and tensile yield strength has been suggested in this paper based on the literature review and presented data. The observed behavior strongly supports the fact that the Hall–Petch of extruded Mg–3Nd–0.5 Zn alloys with different texture intensities cannot be clearly estimated and predicted. In addition, Hall–Petch relations presented in literature can be sufficiently obtained only for fraction of the Mg–3Nd–0.5 Zn alloys.     

挤压Mg-8.5Gd-2.3Y-1.8Ag-0.4Zr合金的显微组织与力学性能(英文)

研究铸态和挤压态Mg-8.5Gd-2.3Y-1.8Ag-0.4Zr合金的显微组织、时效强化和力学性能。铸锭在T4处理后分别于400、450和500°C进行挤压,挤压比为10:1。在细晶强化和析出强化的共同作用下,于400°C挤压的样品经T5处理后可以得到最优的力学性能,所得的晶粒尺寸约为5.0μm,其初始和峰值硬度分别为HV109和HV129。室温下的拉伸屈服强度、抗拉强度和伸长率分别达到391MPa、430MPa和5.2%。     

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.