铸造冷却速度对Mg-4.4Zn-0.3Zr-0.4Y挤压态合金组织性能的影响

本文通过两种不同冷却速度制备成分相同、铸造组织特征不同的Mg-4.4Zn-0.3Zr-0.4Y铸态合金,研究不同铸造组织特征对挤压变形态合金组织和力学性能的影响。研究结果表明：与空冷铸造合金相比较,通过水冷冷却增大了熔体冷却速度,使铸态组织得到细化,抑制了W-相（Mg3Y2Zn3相）的形核,并促进了I-相（Mg3YZn6相）的生成,获得了更大体积分数的准晶相(I-相)。经过挤压变形后,水冷铸造合金中的再结晶晶粒细小均匀,经过挤压变形破碎的细小I-相颗粒弥散分布在基体上,{0002}基面织构得到弱化,而{101 ?2}织构强度增强,从而使挤压态Mg-4.4Zn-0.3Zr-0.4Y合金的强度和塑性都得到了大幅的提高。水冷铸造Mg-4.4Zn-0.3Zr-0.4Y合金经过挤压变形后,屈服强度和抗拉强度分别达到297.0MPa和327.3MPa,与空冷铸造挤压态合金相比分别提高了46.4MPa和21.4MPa。水冷铸造Mg-4.4Zn-0.3Zr-0.4Y挤压态合金的延伸率达到14.8%,与空冷铸造挤压态合金相比增大了4.7%。     

快速凝固粉末冶金Mg_(80)Cu_(10)Y_(10)合金的组织与力学性能

采用快速凝固粉末冶金技术制备热挤压Mg_(80)Cu_(10)Y_(10)合金棒材,研究了快速凝固Mg_(80)Cu_(10)Y_(10)合金薄带及热挤压后合金的相结构,并对热处理工艺对合金棒材组织结构及力学性能的影响进行了分析.研究表明,采用单辊快速凝固法在辊速为1800 r/min下制备的Mg_(80)Cu_(10)Y_(10)合金薄带为完全非晶态;在热挤压过程中Mg_(80)Cu_(10)Y_(10)合金中有Mg_2Cu和Mg晶体相析出,其显微硬度比薄带有所提高,这与合金中细小Mg_2Cu颗粒的弥散析出有关;在450 ℃保温4 h后的热挤压Mg_(80)Cu_(10)Y_(10)合金中没有新相析出;随着热处理温度的升高或保温时间的延长,由于Mg_2Cu颗粒出现重溶及聚集长大现象,使得热挤压Mg_(80)Cu_(10)Y_(10)合金的显微硬度表现出逐渐下降的变化趋势.     

Texture evolution of extruded AZ31 magnesium alloy sheets

The evolution of texture during the annealing and hot rolling process of extruded AZ31 magnesium alloy sheets was studied. There are two kinds of texture components in the extruded AZ31 sheets. One is {0002}<1-010> and the other is {1-010}<1-120>. The {0002}<1-010>component predominates. After annealing at 723 K for 3 h, both {0002}<1-010> and {1-010}<1-120> components are strengthened moderately. This indicates that grains with both two components mentioned above grow faster than those with other orientations. The {1-010}<1-120> component disappears and the intensity of {0002}<1-010> component decreases significantly after hot rolling with a 30% reduction at 623 K. This is mainly attributed to rotational dynamic recrystallization (RDX) during the hot rolling.     

Microstructure and mechanical properties of as-extruded Mg-Sn-Zn-Ca alloy with different extrusion ratios

The effect of extrusion ratio on microstructure and mechanical properties of as-extruded Mg-6Sn-2Zn-1Ca (TZX621) (mass fraction, %) alloy was investigated. It is found that incomplete dynamic recrystallization (DRX) took place in as-extruded TZX621 alloy. As the extrusion ratio was increased from 6 to 16, both fraction of un-DRXed grains and average size of DRXed grains in as-extruded TZX621 alloy decreased and the basal texture was weakened. Coarse CaMgSn phase was broken into particles and fine Mg₂Sn phase precipitated from α-Mg matrix during hot extrusion. Yield strength, ultimate tensile strength and elongation of as-extruded TZX621 alloy with extrusion ratio of 16 reached 226.9 MPa, 295.6 MPa and 18.1%, which were improved by 36.0%, 17.7% and 13.5%, respectively, compared to those of as-extruded TZX621 alloy with extrusion ratio of 6.     

Effects of {10–12} Twins on Dynamic Torsional Properties of Extruded AZ31 Magnesium Alloy

Effects of initial twins on dynamic torsional properties of extruded AZ31 alloy were investigated by introducing {10–12} twins into it through precompression to 3 and 6% strains along the extrusion direction and performing torsional testing at a strain rate of 1.4 × 10³ s^?1 using a torsional Kolsky bar system. The as-extruded sample without twins showed higher dynamic torsional properties than the precompressed samples with many initial twins; the maximum shear strength and fracture shear strain decreased with increasing amount of initial twins. In the as-extruded sample, twinning occurred vigorously throughout the gage section of the tubular specimen during high-strain-rate torsional tests, resulting in heavily deformed morphology, many macrocracks, and rough fractured surfaces. The increased amount of initial twins suppressed the twinning behavior and localized the applied torsional deformation; this resulted in an almost unchanged sample shape, no secondary cracks, and a flat fracture plane, thereby deteriorating the dynamic torsional properties of the extruded alloy.     

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.     

Microstructures and mechanical properties of AZ31-0.1Ca magnesium alloy produced by soft-contact electromagnetic casting and hot extrusion

An AZ31-0.1Ca magnesium alloy produced by Soft-contact electromagnetic continuous casting(SEMC) was investigated.The fine homogeneous structure and the precipitated phases were obtained by SEMC.The effects of microalloying of Ca and middle frequency electromagnetic field on AZ31-0.1Ca magnesium alloy were discussed.And the as-cast billets were extruded with different extrusion ratios subsequently.The alloy showed an ultrafine grain size of 2-5 μm due to dynamic recrytallization(DRX) in the course of hot ext...     

半固态冷却方式对二次挤压Mg-3.88Zn-1.56Gd(wt. %)合金组织和力学性能的影响

本文研究了半固态(淬火或者空冷)以及热挤压对Mg-3.88Zn-1.56Gd(wt. %)合金显微组织和力学性能的影响。结果表明半固态后淬火,第二相在合金中呈现纳米级共晶层片组织,而半固态后空冷,第二相在合金中呈三叉岛、块状和微米层片状。经过二次挤压,由于不完全再结晶,半固态+挤压后的合金均呈现典型的双峰组织。与未半固态直接二次挤压合金相比,半固态+挤压的合金均具有较高的强度。合金性能增强主要原因是由于双峰组织的形成,细小晶粒提供了晶界强化,未再结晶的粗晶粒则是通过抑制基面滑移,从而产生增强效果。其次要原因是准晶相的细化及其在基体中的弥散分布。     

高应变率下热挤压态细晶钨合金的动态力学性能及失效行为

采用快速热挤压技术对细晶93W-4.9Ni-2.1Fe-0.03Y%进行变形强化,研究了高应变率下挤压态细晶钨合金动态力学性能及失效行为。结果表明:在较低应变速率下的挤压态细晶钨合金的屈服强度相近,约2000 MPa;断面上的钨颗粒被严重拉长直至破碎,破碎的细小钨颗粒粘附在软化的粘结相中,随着应变率的增加钨颗粒变形更加明显;剖面观察发现:沿着断裂面的钨颗粒发生了高度的剪切变形,而内部区域则基本没有变形,表现出了剪切局域化迹象。实验结果证明了挤压态细晶钨合金在动态加载条件下的失效方式是绝热剪切失效。     

热挤压快速凝固Mg80Cu15Y5合金棒材的组织与性能

用快速凝固粉末冶金技术制备了直径Φ12mm的Mg80Cu15Y5合金热挤压棒材,并研究该合金薄带、热挤压态及热处理后的组织及力学性能。结果表明:快速凝固Mg80Cu15Y5合金薄带为非晶态,热挤压后的合金棒材中有Mg2Cu、Cu2Y和Mg晶体相析出,热处理后的合金中未有新相析出;随着热处理温度的升高合金棒材的硬度呈现出先升高后降低的趋势,这与合金中Mg2Cu纳米晶颗粒的析出、重溶及长大有关。     

Evolution of microstructure and texture of AZ61 Mg alloy during net-shape pressing of extruded perform

The micro orientation theological behavior of AZ61 Mg alloy during net-shape forming of tensile specimens via close-die pressing of extruded preformed and the effect of the press deformation rate on the microstructure characteristics were characterized with electron back-scattering diffraction (EBSD) orientation imaging microscopy and metallography. The results indicate that the intensity distribution of basal {0001}<10(1)0 > texture on the cross-section of the extruded perform is uniform and parallel to the extrusion direction. Subjected to pressing in extrusion direction, deformation shear stress leads to grain rotation and basal texture {0001}<10(1)0> deviation from the extrusion direction, spreading in the direction perpendicular to pressing direction. The texture intensity increases with the press deformation rate and reaches its peak value at 50%, which is considerably lower than the value reached in extrusion deformation. Then, the texture intensity decreases with the press deformation rate reversely.     

Effect of Mg-based spherical quasicrystal on microstructures and mechanical properties of ZA54 alloy

To improve the strength,toughness and heat-resistance of magnesium alloy,the microstructure and mechanical properties of ZA54 alloy reinforced by icosahedral quasicrystal phase(I-phase) particles were studied.Exceptα-Mg,φ-phase andτ-phase,MgZnYMn I-phase particles can be obtained in ZA54-based composites by the addition of icosahedral quasicrystal-contained Mg-Zn-Y-Mn master alloy.The introduction of MgZnYMn I-phase into ZA54 alloy has great contribution to the refinement of matrix microstructures and the improvement of mechanical properties.When the addition of Mg-based spherical quasicrystal master alloy is up to 3.5%(mass fraction) ,the macro-hardness of ZA54-based composites is increased to HB 68.The impact toughness of composites reaches the peak value of 18.3 J/cm2,which is about 29%higher than that of ZA54 mother alloy.The highest tensile properties at ambient and elevated temperatures with master alloy addition of 2.5%(473 K) are also obtained in ZA54-based composites with 3.5%(mass fraction) Mg-Zn-Y-Mn master alloy addition.The ultimate tensile strength of composites at ambient and elevated temperatures are 192.5 MPa and 174 MPa,which are 23.4%and 33.8%higher than that of ZA54 mother alloy,respectively. The improved mechanical properties are mainly attributed to the pinning effect of I-phase on grain boundaries.     

Mg-3Y合金大应变量轧制过程中的孪生辅助动态再结晶及组织演变

采用预挤压加单道次大应变量热轧制的方法制备了Mg-3Y（质量分数,%）合金板材。并研究了大应变量轧制过程中不同孪晶类型对合金动态再结晶（DRX）及组织演变的影响。结果表明,在挤压比为8:1的预挤压过程中,合金内部发生了几乎完全的动态再结晶。而在接下来的大应变量热轧制过程中,孪生变形尤其是■压缩孪晶及■双孪晶在协调合金的塑性应变中发挥了重要作用。此外,大量动态再结晶在压缩孪晶及双孪晶内部发生,并扩展到非孪晶区域,有效缓解了轧制过程中的内应力集中。上述2个过程对提高合金在大应变量轧制中的成形性均起到了促进作用。     

连铸AZ31镁合金的热挤压变形组织与性能(英文)

文章研究了电磁连铸AZ31镁合金经热挤压变形后的微观组织和力学性能。结果表明,挤压过程中的动态再结晶能够显著细化晶粒,局部细晶区的平均晶粒为2μm。与铸态合金相比,挤压后的AZ31镁合金具有更细小的晶粒和更均匀的微观组织。挤压变形后产生强烈的基面织构;挤压后材料的力学性能显著提高。屈服强度、抗拉强度和断面收缩率随着挤压比的增大而增大。挤压比为25时,屈服强度、抗拉强度和断面收缩率分别为259MPa,357MPa和30.5%,比铸态合金分别提高了86.33%,64.52%和67.40%。随着挤压比的增大,晶粒细化效果更为明显,微观组织更均匀。断口形貌分析表明,挤压变形后材料由韧脆混合型断裂,转变为韧性断裂。     

Microstructure Formation and Mechanical Property Involving Icosahedral Quasicrystal Phase of Y Rich Mg-Zn-Y Quasicrystal Alloy

The microstructure formation and mechanical property involving icosahedral quasicrystal (I-phase) in the Y-rich Mg-Zn-Y alloy have been studied. The equilibrium formation of I-phase from the Y-rich Mg-Zn-Y melt is through a peritectic reaction between the Y-rich melt and the primary W-phase, which is discussed in detail. The independent nucleation and coupling growth mechanism between the W-phase and the I-phase, from the melt, are revealed, which is significant for understanding the peritectic reaction process involving icosahedral quasicrystal in the Mg-Zn-Y alloy. The mechanism of the quasicrystal phase strengthened magnesium alloys is also discussed here.     

SiC_p/AZ91镁基复合材料的热挤压

采用搅拌铸造法制备SiC体积分数为5%、10%和15%的颗粒增强AZ91镁基复合材料（SiCp/AZ91）。复合材料经过T4处理后,于350°C以固定挤压比12：1进行热挤压。在铸态复合材料中,颗粒在晶间微观区域发生偏聚。热挤压基本上消除了这种偏聚并有效地改善颗粒分布。另外,热挤压有效地细化基体的晶粒。结果表明：热挤压明显提高复合材料的力学性能。在挤压态复合材料中,随着SiC颗粒含量的升高,基体的晶粒尺寸减小,强度和弹性模量升高,但是伸长率降低。     

Microstructure and Texture Evolution During the Direct Extrusion and Bending–Shear Deformation of AZ31 Magnesium Alloy

AZ31 alloys were extruded by direct extrusion and bending–shear deformation(DEBS). The microstructure characteristic and texture evolution of DEBSed AZ31 sheets were investigated by electron backscattered diffraction(EBSD). It is found that DEBS technique could effectively refine grains and weaken texture. Besides, we also investigate how twinning affects dynamic recrystallization during hot extrusion. {10–12} extension twins can offer nucleation sites and enough energy to trigger dynamic recrystallization. Moreover, the character of direct extrusion and bending–shear die can lead to the activation of non-basal slip system and further dramatically weaken the basal texture of the microstructure with many preactivated basal slip systems.     

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 tensile properties of as-extruded Mg-Sn-Y alloys

The microstructure and tensile properties of the Mg-1.0%Sn-xY(x=1.5%,3.0%,3.5%,atom fraction)alloys extruded indirectly at 350℃ were investigated by means of optical microscopy,scanning electron microscopy and tensile test.The mean grain sizes ofα-Mg matrix in the three extruded alloys are 6,8 and 12μm,respectively,slightly increasing with the addition of Y. The relationship between microstructure and strength was discussed in detail.The results show that the addition of Y has little effect on the grain refinement of the as-extruded Mg-Sn based alloys above.The only MgSnY phase is detected in the Mg-Sn-1.5%Y alloy, and the Sn3Y5 phase in the Mg-Sn-3.5%Y alloy,whereas both of them simultaneously exist in the Mg-Sn-3.0%Y alloy.The particle shape of MgSnY and Sn3Y5 phase,inherited from the solidification,has little change before and after hot extrusion.Mg-Sn-3.0%Y alloy has the highest ultimate tensile strength(UTS),305 MPa,by over 50%compared with that of the other two alloys.     

Microstructure and properties of hot extruded AZ31-0.25%Sb Mg-alloy

The effects of hot extrusion treatment on the microstructure and mechanical properties of AZ31-0.25%Sb Mg alloy were investigated by means of mechanical properties measurement and microstructure observation.The results show that the microstructure of AZ31-0.25%Sb Mg alloys consists ofα-Ms matrix,Mg_(17)Al_(12) and Mg_3Sb_2 phases.The ultimate tensile strength (UTS) and yield tensile strength(YTS) of the alloy are obviously enhanced by hot extrusion treatment,and the enhanced extent of UTS and YTS increas...