激光毛化对3003铝合金织构及性能的影响

采用不同粗糙度的YAG激光毛化冷轧辊对3003铝合金板进行不同变形量的冷轧,利用取向分布函数(Orientation Distribution Functions)探讨了采用激光毛化冷轧辊轧制条件下3003铝合金变形织构随冷轧变形量的变化过程.结果表明:经激光毛化辊轧制后的铝板,其强度与普通板接近,但塑性高于普通板.采用激光毛化辊轧制在样品中产生相对较强的S织构{123}〈634〉,其强度随冷轧变形量增加而增强.在90%变形量时,样品中产生较强的旋转立方取向{001}〈110〉,随着变形量的增加,此旋转立方取向的强度逐渐减少并消失.样品中还含有少量的Cu织构、Brass织构及少量的Goss织构组分.     

3300四辊可逆轧制1050A纯铝板材工艺

介绍了在3300mm四辊可逆式热轧机上轧制纯铝1050A板材的轧制工艺。结合"地铁铝/钢感应板"的研发,通过设计合理的变形方式,采用一火500℃/15h,二火460℃/1.5～2h的加热制度,确定合理的辊型、压下制度,轧制出外形尺寸、同板差、力学性能等各项技术指标均满足技术标准GB/T3880—1997及科研协议的成品铝板。     

表面机械研磨对5052铝合金表面纳米化与性能的影响

研究了表面机械研磨处理(SMAT)对传统轧制和连铸连轧5052铝合金显微组织、物相组成、硬度和拉伸性能的影响。结果表明:进行SMAT前,连铸连轧5052铝合金的晶粒尺寸(7μm)要小于传统轧制5052铝合金的晶粒尺寸(13μm);进行SMAT后,传统轧制和连铸连轧5052铝合金在表层均会形成细小的晶粒尺寸梯度分布,而且传统轧制和连铸连轧的5052铝合金的心部硬度和表层硬度均会有不同程度的提高,经过5.0 min的SMAT后,心部硬度分别达到89和91 HV,表面硬度基本相当(约为102 HV);相同SMAT时间下,连铸连轧5052铝合金的抗拉强度和断后伸长率均要高于传统轧制的5052铝合金,当SMAT时间增加至1.0 min及以上时,传统轧制和连铸连轧5052铝合金的抗拉强度有明显提升、断后伸长率略有减小,这主要与SMAT后合金表层形成了一定厚度的加工硬化和细晶强化层有关。     

轧制方式对工业纯钛TA2轧板织构演变的影响

开展了轧制方式对工业纯钛TA2板的织构演变的影响研究。通过3种轧制方式,即等温轧制、差温轧制和反复弯轧进行试验,其中差温轧制的上辊温度高于下辊温度90℃,反复弯轧则是差温带异步轧制,并进行正弯和反弯变形。轧制后的3种钛材采用EBSD手段分析晶粒取向和织构变化。结果显示3种轧制方式获得钛板的变形织构出现明显差异,等温轧制变形织构与典型的α-Ti轧制织构类似,差别仅在于主要峰位置的角度有稍许偏移,其变形大晶粒和再结晶细晶取向沿0001//RD;差温轧制的变形织构为柱面织构,晶粒取向为21 10//RD。其主要原因是上下辊表面温度差异诱发材料厚向产生均匀一致的剪应变,这类似于等通道挤压变形的效果。而反复弯轧的织构同时存在基面织构与锥面织构等变形织构组分,但锥面织构占主导,其细晶取向除沿较强的0001//RD方向外,还沿其他2个较弱的取向21 12//RD和21 13//RD。     

非对称轧制AZ31镁合金板材组织与性能

采用商用连铸连轧AZ31镁合金板材,通过小辊径非对称轧制工艺,研究在150,200,250℃温度条件下多道次非对称轧制对镁合金板材组织、织构和力学性能的影响。结果表明,不同轧制温度下,镁合金板材的晶粒细化机理不同,150℃时以孪晶细化为主,部分晶粒发生动态再结晶,200和250℃时板材晶粒细化机理为动态再结晶。对比分析了对称轧制和非对称轧制板材织构演化规律,随着轧制温度的升高,非对称轧制板材基面织构依次增强,但明显低于对称轧制板材。     

连轧和可逆轧工艺对B441铁素体不锈钢成形性能的影响

采用二十辊轧和四连轧两种不同的轧制工艺生产了B441铁素体不锈钢冷轧板,在相同压下率下经相同的退火、酸洗处理,比较了两种冷轧工艺的成品板力学性能,研究了不同轧制工艺下成品板的微观组织和宏观织构。研究了不同轧制方式对B441铁素体不锈钢织构演变和成形性能的影响。结果表明:四连轧在相同退火(990℃保温2 min)下再结晶更容易。四连轧经退火后B441成品板屈服强度、抗拉强度和伸长率均略小于二十辊轧制退火后的成品板。四连轧试样中心层织构主要为{111}112。     

焊接参数对7075铝合金搅拌摩擦焊接头组织及性能的影响

使用搅拌摩擦焊(FSW)设备,采用不同搅拌针转速和焊速对厚6 mm的7075高强铝合金平板进行对接试验,并对不同焊接工艺下的接头进行微观组织观察和力学性能测试。研究结果表明:7075铝合金FSW接头由焊核区(WNZ)、热机影响区(TMAZ)、热影响区(HAZ)及母材区(BMZ)组成;随着搅拌针转速的增大,接头中焊核区的晶粒越大;随着焊速的增大,接头中焊核区晶粒越细小;不同工艺参数下的FSW接头显微硬度分布曲线都呈W形。随着转速的提高和焊速的减小,接头显微硬度升高,但波动范围较小;随着转速和焊速的提高,接头抗拉强度先降低后提高;转速为400 r/min,焊速为120 mm/min时,接头抗拉强度最高,为417 MPa,是厚6 mm的7075铝合金FSW最佳的工艺参数。     

AZ31B镁合金管材纵连轧损伤与温度场探索性研究

在轧制温度为350℃,轧辊角速度约为3.14 r/s,壁厚压下量分别为20(4)、30(4)、40(4)的条件下,对尺寸为50 mm×7 mm×1000 mm的AZ31B镁合金管进行纵连轧热力耦合数值模拟,在相同温度不同压下量的轧制条件下,从轧制损伤的应力状态和温度场分布两方面对镁合金管材纵连轧的数值模拟结果进行了探索性研究。结果表明:在相同轧制温度条件下,随着压下量的增大,最大损伤值也随着增大,且最大损伤值均出现在轧辊的辊缝处。同时塑性变形产生的热量也增大,且因轧辊辊顶处和镁管间存在较大的热交换,所以辊缝处的温度要高于辊顶处,两者之间有一定的温度差,壁厚压下量越大则温度差越大。相同压下量条件下,纵连轧镁合金管的损伤程度要比镁合金板材轧制的小。     

日本连轧管机高精度轧制技术的开发

日本住友金属工业公司综合材料研究所开发出在二辊式连轧管机第5机架后配制四辊式机架(1机架)的高精度轧制方法,改善了连轧管机成品机架造成的钢管壁厚不均。介绍了该所为验证壁厚矫正效果,用实验轧机(实际轧机的1/6)进行的模拟试验,试验方法及结果。研究结果表明,四辊式机架可矫正连轧管机轧制钢管壁厚不均的80%。     

世界铝平轧工业一览(1)

对全世界铝平轧产品（板、带、箔）工业作了全面系统的调查、概括与简要的分析、归纳。截止到2006年底,全球共有板、带、箔生产企业约700个,其中中国有约350个;生产铝平轧产品的国家与地区69个,总生产能力约24 000kt/a（中国约4 070 kt/a）;铝板带厂456个,总生产能力约20 000 kt/a;铝箔厂约258个,总生产能力约4 000 kt/a;铸锭热轧机及生产线约155台/条;黑兹莱特连铸连轧生产线12条,劳纳连铸连轧线1条（生产能力约300 kt/a）,它们的总生产能力约1 800 kt/a;二辊式连续铸轧机线约590条,总生产能力约6 000 kt/a,中国约有265条,总产能约2 200 kt/a;铸锭热轧生产能力（含二辊块片轧机的）约23 000 kt/a,连铸连轧及连续铸轧的总生产能力约7 800 kt/a,前者占总生产能力的74.7%,后二者占总生产能力的25%强,在2006年约17 000 kt铝平轧产品中,连续铸轧及铸连轧供坯的产量约6 200 kt,占36.5%;辊面宽度大于、等于800 mm的四辊冷连轧生产线及冷轧机约570台（条）;工作辊直径等于、小于280 mm的四辊箔轧机约523台。 全文共分三部分：第一部分———基本资料,第二部分———全球69个国家与地区438个工厂的简况、地址与生产能力;第三部分———世界对铝平轧产品的需求。本期刊登第一部分。     

Process–structure–property relationships for nugget and heat affected zone regions of AA2524–T351 friction stir welds

Abstract

The effects of weld tool rotational speed ω, welding speed v and z-axis force F_Z during friction stir welding of the aluminium alloy 2524-T351 on the resulting process response variables, nugget microstructure, nugget tensile properties and heat affected zone hardness variations were investigated. For the range of conditions examined, the results indicate that ω has the dominant effect on nugget properties and structure, that optimum nugget tensile properties can be obtained by increasing ω to obtain a peak temperature that is just below the incipient local melting temperature, and that excessive values of ω result in low nugget ductility because of localised embrittlement near the weld crown. The study has also shown that the peak weld temperature is inversely related to the measured torque T ₀. The T ₀–ω relationship appears to be a useful guide for weld modification, as it is indicative of conditions leading to overheating in the nugget region.     

Variations in the microstructure and mechanical properties of the oxide layer on high speed steel hot rolling work rolls

This paper is part of a larger study to understand the wear of hot rolling rolls. A significant cost of the hot rolling process is associated with the consumption of rolls, which is why a comprehensive understanding of the wear of the roll material is important. Given that the surface of the rolls is covered by an oxide layer, it is important to know the tribological and mechanical properties of the oxides. Research in this area concentrates mainly on the morphologies and microstructures of the oxide layers. Previously published works give very little, if any, information of the mechanical properties of the layers on high speed steel. This paper presents a methodology to study the mechanical properties of the oxide layer formed on the surface of a high speed steel roll using combined nanoindentation tests and finite element simulations. Mechanical properties such as the elastic modulus (E), hardness (H), yield strength (σ_y), and Poisson's ratio (ν), have been determined, and the work has revealed a variation of microstructure, porosity (f), and mechanical properties of the oxide layer across its thickness. The outer sub-layer has a higher E and H than the inner sub-layer. This variation of mechanical properties in the oxide layer was consistent with variations in the porosity and grain sizes in the two sub-layers.     

终轧工艺对AM50镁合金轧板力学性能和织构特征的影响

采用不同的轧辊温度和速率制备AM50镁合金轧板,研究终轧工艺对镁板力学性能和织构特征的影响。研究表明：在轧辊温度为200°C和轧辊速率为5 m/min条件下制备的镁板的强度（极限抗拉强度：295 MPa;屈服强度：224 MPa）和伸长率（22.9%）之间达到较优组合;在热轧过程中,轧板的屈服强度主要取决于轧制温度,而织构强度则对轧辊速率更为敏感;提高轧制温度或轧辊速率均可改善AM50镁合金板材力学性能的各性异性。     

大型轧机差径等转速轧制时轧制力矩分配

对大型轧机的相同转速、不同直径轧辊的力矩分配进行了理论分析和模拟实验，并由此提出，大型轧机不同辊径等转速带“下压力”轧制时，应考虑锭重和轧件运动加速度对轧制力矩的影响，轧机下辊应选用较大的电机才能充分发挥轧机的能力。     

Effect of deformation temperature on microstructures and properties of 7075/6009 alloy

The 7075/6009 aluminum composite ingot with the diameter of 65 mm was prepared by double-stream-pouring continuous casting. The deformation behavior and the mechanical properties of the composite ingot compressed at 543, 573, 623, 673 and 723 K were analyzed. The results show that the gradient distributions of composition and hardness in the transition layer of the composite plates still exist after plastic deformation of the ingots. Meanwhile, the thickness of the transition layer reduces from millimeter order to micrometer order. The mechanical properties of the composite plate increase with the increase in deformation temperature from 543 K to 673 K. The best mechanical properties of the 7075/6009 aluminum composite are: σ_b=381 MPa, σ_0.2=322 MPa and δ=16.6%. The appropriate deformation temperature range is (0.75–0.85)T_M, where T_M is the melting point of 7075 alloy.     

Synthesis of aluminum alloy 7075-graphite composites by milling processes and hot extrusion

Aluminum alloy 7075 (Al₇₀₇₅) and composites of Al₇₀₇₅ with different concentrations of graphite particles (Al₇₀₇₅-G) were synthesized from elemental powders by a milling process. Milled products were consolidated by pressureless-sintering followed by hot extrusion. The mechanical properties of the sintered specimens were evaluated by tension tests and hardness measurements. Variation of Zn and graphite contents and their effect on mechanical properties was characterized. The results obtained show that the yield strength (σ_y), the maximum strength (σ_max) and the Vickers microhardness (μHV) were enhanced as a function of graphite particles content and milling time, but the elongation was reduced significantly in some cases.     

Electrochemical nucleation and growth of aluminum nanoparticles and leaf-like flat microstructures from reline deep eutectic solvent: Effect of temperature and angular speed of working electrode

The main objective of this work was to use reline deep eutectic solvent, containing Al(III) ions, for the electrochemical study of the nucleation and growth of aluminum onto a glassy carbon electrode at different temperatures and angular speeds (ω) of the working electrode. In order to fulfill this, electrochemical and surface characterization techniques were used. It was found that as temperature increased, the onset of the Al(III)_DES reduction occurred at less negative potentials while the current peak of the voltammograms increased. These indicate that Al deposition thermodynamics and kinetics were favored. Practically, no anodic current was detected due to Al passivation by Al(OH)₃(s) and γ-Al₂O₃(s). At ω=0 r/min, the Al deposition chronoamperograms were analyzed by a theoretical model comprising Al 3D diffusion-controlled nucleation and growth and residual water reduction. However, those recorded at different angular speeds were analyzed with a theoretical model where adsorption?desorption and diffusion-controlled nucleation?growth occurred simultaneously. The deposits were characterized by SEM, EDX, XPS and XRD. At ω=0 r/min, formation of well distributed nanoparticles ((78.1±9.5) nm) was observed, while at ω=900 r/min the deposit was formed by multiple 10 μm diameter leaf-like flat microstructures, composed by Al, Al(OH)₃(s) and γ-A₂O₃(s).     

An Investigation into Microstructures and Mechanical Properties of AA7075-T6 during Friction Stir Welding at Relatively High Rotational Speeds

In this study, microstructural changes and mechanical properties during friction stir welding of AA7075-T6 have been investigated. Friction stir welding at relatively high rotational speeds ranging from 1000 to 1400 rpm and longitudinal speeds in the range of 40 to 80 mm/min have been performed and then microstructures and mechanical properties of the weldments have been studied. The results show that the rotational and longitudinal speeds have a significant effect on the microstructures as well as the mechanical behavior of the welded material while a fine grain structure is produced at higher ratio of rotational speed to longitudinal speed. On the other hand, for a given longitudinal speed, it is revealed that there is an optimum rotational speed which gives the highest tensile strength and elongation for the stirred zone.     

中厚板纵向边裂产生原因与控制方法

针对中厚板纵向边裂问题,研究了其形成机理,对轧钢工序中加热制度,上、下工作辊辊径,辊速配比对钢板上、下表面边部变形均匀性的影响进行了工业试验研究。结果表明,通过调整加热制度及上、下工作辊辊速可改善钢板上、下表面变形均匀性,将钢板下表面边裂控制在距边部30mm内,钢板切边后可以完全消除纵向边裂,使钢板合格率达90%以上。     

Friction stir welding of dissimilar A319 and A356 aluminium cast alloys

Abstract

In the present investigation, the microstructure and mechanical characteristics of dissimilar A319 and A356 cast Al alloys plates joined by friction stir welding (FSW) were evaluated. The effect of tool rotational and welding speeds as well as the post-weld heat treatment (PWHT) on such properties was investigated. Post-weld heat treatment was carried out at a solutionising temperature of 540°C for 12 h followed by aging at 155°C for 6 h. For the as welded specimens, the welded zone (WZ) exhibited higher hardness values when compared with the A319 and A356 parent alloys. The peak hardness at the WZ was found to increase by increasing the tool rotational speed and/or reducing the welding speed. In contrast, the post-weld heat treated (PWHTed) specimens exhibited lower hardness values at the WZ than the parent alloys. For PWHTed specimens, the peak hardness at the WZ was found to decrease by increasing the tool rotational speed and/or reducing the welding speed. Tensile tests results demonstrate that, for the as welded specimens, the tensile fracture took place on A356 side where the hardness was minimal. While for PWHTed specimens, the fracture took place at the WZ. Increasing the tool rotational speed reducing both tensile and yield strengths, but increases the ductility of the joint.