压印模具表面织构电火花成形工艺参数的分析

在石墨电极表面制备了直径分别为ø100、ø200和ø300 μm且具有规则形貌的圆形微凹坑阵列,并使用该电极在45钢表面利用电火花成形工艺(Electrical discharge machining,EDM)制备出微凸起阵列压印模具,研究了加工电流对其表面性能的影响。采用超景深显微镜和扫描电镜对经电火花加工处理后的石墨电极和45钢试样的表面形貌进行了分析,同时采用洛氏硬度计、粗糙度测试仪和精度为0.01 mg的电子天平秤等设备对45钢表面微凸起阵列进行了检测,并讨论了加工电流对45钢的材料去除率(Material removal rate,MRR)和石墨电极的电极耗损率(Electrode wear rate,EWR)之间的影响规律。结果表明,电火花反刻原理可以在45钢表面形成尺寸相对应的微凸起阵列形貌,并得到较高的表面显微硬度和表面粗糙度值,随着电火花加工电流的增大而增大,其中,ø200 μm微凸起试样得到了最大显微硬度,为34 HRC,同时,ø300 μm微凸起试样得到了最大表面粗糙度值12.56 μm。此外,当试样微凹坑或微凸起直径一定时,随着加工电流的增大,MRR和EWR值也会随之增大。     

工艺参数对高速电镀锌层形貌和织构的影响

应用模拟重力法高速电镀装置在无间隙原子钢(IF钢)基板上电镀锌,采用场发射扫描电镜(FESEM)和X射线衍射仪(XRD)研究电流密度和钢板运动速度对锌层微观形貌和织构的影响。结果表明:高速电镀锌层呈片晶状倾斜于基体表面紧密排列,随着电流密度(20~60 A/dm2)的增大,{10.3}和{10.4}等锥形织构系数降低,{00.2}基面织构系数显著增加,晶粒尺寸减小;当电流密度高于50 A/dm2时,伴有枝晶的出现;钢板运动速度(1~3 m/s)的增大提高镀层的致密度,同时降低{00.2}基面织构系数,对锥形织构的影响较小。     

变形参数对AZ31镁合金板材织构的影响

利用X射线衍射(XRD)方法测量了不同轧制状态,即不同变形温度和变形量条件下AZ31镁合金板材织构的变化特征。结果表明,经过轧制之后的AZ31镁合金板材形成强烈的基面织构;在250℃~400℃范围内,变形温度的升高、变形量的增大都会促进镁合金板材棱柱面、锥面等非基面滑移系的启动,从而影响各织构组分的锋锐程度和板材各向异性的强弱。随着变形温度的升高,镁合金板材的各向异性减弱;变形量的增大,镁合金板材的各向异性增强。     

Determination of material parameters and texture of a polycrystalline aggregate from ultrasonic measurements

The propagation of ultrasonic waves in a polycrystalline aggregate is considered for a bulk sample with orthorhombic symmetry made of cubic crystals of the highest symmetry. The probability density function of the crystallite orientation and the stiffness moduli of a single grain (crystallite) of the polycrystalline aggregate are found from four ultrasonic velocities and the rules of orthorhombic symmetry. Moreover, Jaynes’ principle of maximum Shannon entropy and the averaging procedure proposed by Voigt are used. In this way, it is shown that on the basis of the measurements of four respectively chosen ultrasonic velocities it is possible to find simultaneously the maximum-entropy distribution function of the crystallite orientation and the crystallite stiffness moduli.     

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.     

Effects of deformation parameters on microstructure and texture of Mg–Zn–Ce alloy

Compression tests were performed on the Mg–6Zn–0.5Ce (wt.%) alloy using a Gleeble–1500 thermo- mechanical simulator testing system at temperatures of 250, 300, 350 °C and strain rates of 0.001, 0.01, 0.1 s⁻¹. The microstructure and texture evolution of the Mg–6Zn–0.5Ce alloy during hot compression were investigated by optical microscopy (OM) and electron backscattered diffraction (EBSD). The results showed that Zener–Hollomon parameters obtained from the deformation processes had a significant effect on the dynamic recrystallization and texture of the Mg–6Zn–0.5Ce alloy. The fraction of undynamically recrystallized (unDRXed) regions increased, and the dynamically recrystallized (DRXed) grain size decreased with increasing the Zener–Hollomon parameters. The texture intensity of the DRXed regions was weaker compared with that in the unDRXed regions, which resulted in a sharper texture intensity in the samples deformed with higher Zener–Hollomon parameters. The increase in recrystallized texture intensity was related to preferred grain growth.     

工艺参数对冷轧无取向硅钢再结晶织构的影响

分析了硅含量为2.0 wt%的高牌号冷轧无取向硅钢冷轧变形量和不同退火温度对再结晶织构及晶粒尺寸的影响。结果表明,热轧板表面与心部组织和织构的差异对后续冷轧和再结晶退火的织构和晶粒尺寸有明显影响。热轧板表面的退火态晶粒组织使其织构转变滞后于心部,并可造成最终退火后较强的{001}〈110〉织构和均匀的{111}织构,有利于磁性的改善。提高冷变形量会增加再结晶形核率而减小晶粒尺寸,提高再结晶温度不明显改变再结晶织构但增大晶粒尺寸,但应防止过高温度下析出相粒子的回溶。分析表明,热轧板常化工艺,以及二次冷轧加中间退火工艺均有利于改善钢板成品织构,进而改善钢板磁性能。     

Research on optimal laser texture parameters about antifriction characteristics of cemented carbide surface

Cemented carbide (YG8) is commonly applied to workplaces where friction and wear are severe. Therefore, improving the surface friction performance is of great significance. Surface micro-texture technology is exactly a feasible method. However, due to high wear resistance and hardness of YG8, it is difficult to process surface texture with accurate feature size by traditional methods. In this paper, four types of groove-shaped textures were etched on the surface of YG8 discs by high peak power UV nanosecond laser. The error of texture width could be controlled within ±5 μm. Friction and wear tests were performed using a standard ball-on-disc configuration to investigate the influence of the texture parameters (width and area ratio of grooved textures) on the friction-reducing and wear-resistance properties under constant load and relative sliding speed. Antifriction mechanism of textures was analyzed and a theoretical model of texture under dry friction condition was presented. As shown in the experimental results, the optimal texture parameters have a good gain effect on friction-reducing and wear-resistance of cemented carbide surface under dry friction and solid lubrication. Friction coefficient was reduced from 0.301 to 0.275 and 0.138, respectively. The theoretical model has good agreement with the experimental data and could provide theoretical support for predicting the optimal parameters of texture.     

Mg sheet: the effect of process parameters and alloy composition on texture and mechanical properties

The paper addresses the relationship between microstructure, texture, and mechanical properties of rolled magnesium sheets. The effect of rolling temperature and alloying elements on texture development and mechanical properties is demonstrated. Special focus is paid to the potential of rare earth elements to modify the anisotropic behavior and to weaken the strong basal texture of magnesium sheets. Alloy design that considers these possibilities together with appropriate selection of process parameters show the road to magnesium sheets with improved forming properties.     

旋压参数对TC21钛合金筒形件旋压织构的影响

通过二次开发将晶体塑性滑移模型嵌入ABAQUS商业软件,对TC21钛合金筒形件旋压织构演变进行了有限元数值模拟,研究了旋压工艺参数对合金筒形件旋压织构组分和织构强度的影响.结果表明,实验与模拟结果对比显示出采用晶体塑性模型模拟织构演变时具有较高可靠性.减薄率显著影响旋压织构的组分和强度,当减薄率＜25％时,织构组分主要为(0001)<2(11)0>,当减薄率＞30％时,织构组分主要为(0001)<2(11)0>、(10(1)3)、(0001)及(10(1)0)织构,且织构强度随减薄率增加而增大.主轴转速和进给速度不明显改变织构组分,主要为(10(1)3)、(0001)及(10(1)0)纤维织构.随主轴转速和进给速度增加,(10(1)3)、(0001)及(10(1)0)织构强度增大.     

The effect of cold rolling parameters on the recrystallization texture of non-oriented electrical steel

The effect of cold rolling condition on magnetic properties of non-oriented electrical steel was investigated. For evaluation of cold roiling condition, utilizing rolling shape factor (RSF) was proposed. In the case of small RSF, magnetic induction was improved. Development of ND ∥ <111< components was suppressed in the recrystallized texture near the surface, and the vicinity of the {100}<001> component was developed after grain growth. The relation between RSF and cold-rolling condition was examined by computer simulation; such results were attributed to the increment of shear strain in the surface texture. Magnetic properties would be improved by adequate control of cold-rolling condition.     

磁过滤等离子体制备TiN薄膜中沉积条件对薄膜织构的影响

在室温条件下,利用自行设计的平面"S"形磁过滤等离子体设备,在(111)面单晶硅上制备TiN薄膜,通过改变基底偏压和反应气体成分,即通过改变氮气和氩气的气体流量来改变沉积离子的能量和密度,从离子轰击的角度研究了沉积条件对TiN薄膜织构的影响.对薄膜的表面形貌进行观察,用(θ～2θ)和1.5°掠入射2种X射线衍射方法对薄膜晶体结构和晶面取向进行了分析,对薄膜进行了电子衍射研究.结果显示磁过滤等离子制备的TiN薄膜表面平整光滑,颗粒尺寸为20～70 nm,且基底偏压和氩气流量的增大促使薄膜发生(111)面的择优取向,且(111)晶面与膜表面平行,而在高氩气流量的情况下,(200)和(220)面在薄膜平面也发生了定向排列.     

Effect of processing parameters on the densification,microstructure and crystallographic texture during the laser powder bed fusion of pure tungsten

Laser Powder Bed Fusion is a leading additive manufacturing technology, which has been used successfully with a range of lower melting point materials (titanium alloys, nickel alloys, steels). This work looks to extend its use to refractory metals, such as those considered in this paper where the behaviour of pure tungsten powder is investigated. A strategy for fabricating high density parts was developed by creating a process map in which the effect of laser energy density was studied. The process quality was assessed using different techniques including light optical microscopy, XCT, SEM and EBSD. The results showed that the laser energy density was adequate to process tungsten to produce functional parts. The bulk density and optically determined densities, under different process conditions, ranged from 94 to 98%, but there was evidence of micro cracks and defects in specimens due to micro- and macro-scale residual stress. Analysis of the microstructure and local crystallographic texture showed that the melt pool formed under the laser beam favoured solidification in a preferred orientation by an epitaxial growth mechanism. The EBSD local texture analysis of the tungsten specimens showed a <111>//Z preferential fibre texture, parallel to the build direction.     

精细电规准对NAK80材料准镜面电火花加工表面三维幅值参数的影响

通过正交试验,研究了峰值电流、脉冲间隔、开路电压、脉冲宽度等精细电规准在不同水平下,对NAK80材料准镜面电火花加工的三维表面参数(Sa、Sq和Sz)的影响。试验结果显示,在上述因素中,峰值电流和脉冲间隔对评价指标影响较大,脉冲宽度影响最小。通过方差分析,试验选定因素对评价指标的影响均非显著,并通过信噪比获得最优的加工参数。     

Al-1.8Cu-0.4Mg-0.4Mn合金一次冷轧织构与二次冷轧织构的研究

将Al-1.8Cu-0.4Mg-0.4Mn合金进行50%、60%、70%、80%不同压下量的一次冷轧,随后分别将一次冷轧压下率为50%和70%的样品进行等温中间退火并进行80%压下率的二次冷轧,对其织构演变过程进行研究。研究结果表明,当压下量大于60%时,一次冷轧的样品呈现“铜式”织构特征,即在α、β取向线上分布G、B、C及S组分,C、B和S组分强度随变形量的增加而增大,G组分则先增大后减小,在70%变形量时达最大。中间退火再结晶织构较弥散,但中间退火对二次冷轧织构有较大影响。初次冷轧变形量50%的样品形成弱的{001}<110>旋转立方织构,初次冷轧变形量70%的样品形成“铜式”织构。     

冷轧高纯铝箔初始织构对再结晶织构的影响

高压箔经过多道次冷轧后,形成类型复杂的织构。本试验应用X射线衍射仪测定铝箔织构,定量研究了冷轧高纯铝箔常见初始织构与再结晶织构的关系。结果表明,当初始织构为高含量的S织构{123}<634>、铜织构{112}<111>和约10%的立方织构{100}<001>,较少的旋转立方{001}<110>、黄铜织构{011}<211>时,再结晶退火后立方织构含量最高。由于S织构与立方织构存在40°<111>关系,在退火过程中有利于形成立方织构。