挤压及热处理对6063铝合金组织及性能的影响

对6063铝合金采用了等通道转角挤压工艺及随后的热处理,利用光学显微镜、扫描电子显微镜及拉伸实验分析了挤压及热处理对6063铝合金的微观组织及力学性能的影响。研究表明:等通道转角挤压显著细化了铝合金的晶粒尺寸并改善了晶粒分布的均匀性。挤压道次越多,晶粒细化作用越明显且晶粒分布的均匀性也越好。经4道次挤压及时效处理后,铝合金的平均晶粒尺寸减小到1.3μm,材料的强度和硬度得到显著提高而延伸率仍保持较高。增强的强度及硬度归功于位错强化、晶界强化和析出的Mg2Si相。     

偏心距对偏心挤压一次成型铝合金弯管的影响

通过Deform-3D有限元软件分析了偏心距对5052铝合金弯管曲率的影响,得到在不同偏心距下的曲率-行程曲线.结果表明,在弯曲过程中管材随着偏心距的增大呈现的弯曲越大.在同一偏心距下,弯管的曲率与行程之间呈线性变化.同时也得到了偏心距与曲率斜率之间的关系.     

Effect of internal fluid pressure on quality of aluminum alloy tube in rotary draw bending

In the present study, the rotary draw bending of aluminum alloy tubes with internal fluid pressure is investigated by finite element simulation and experiments. The effect of the internal pressure on the cross-section ovality, wall thinning, and wall thickening was studied. The results show that the internal pressure has a significant effect on cross-section quality of aluminum alloy bent tubes. As the internal pressure increases, the cross-section ovality and the wall thickening decrease, and the wall thinning increases. The effect of internal pressure on wall thinning is more significant than its effect on wall thickening.     

Parameter prediction in laser bending of aluminum alloy sheet

Based on the basic platform of BP neural networks, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1–2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indicate that the prediction allowance is controlled less than 5%–8% and can provide a theoretical and experimental basis for industry purpose.     

Parameter prediction in laser bending of aluminum alloy sheet

Based on the basic platform of BP neural networks, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1–2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indicate that the prediction allowance is controlled less than 5%–8% and can provide a theoretical and experimental basis for industry purpose. __________ Translated from Optics and Precision Engineering, 2007, 15(6): 915–921 [译自: 光学精密工程     

Energy absorption of aluminum alloy thin-walled tubes under axial impact

Aluminum alloys are important technological materials for achieving the lightweight design of automotive structures. Many works have reported on the deformation and energy absorption of thin-walled tubes. Multicorner tubes with extra concave corners in the cross section were presented in this study to improve the energy absorption efficiency of aluminum alloy thin-walled tubes. The axial crushing of square and multicorner thin-walled tubes was simulated with the same cross-sectional perimeter. The method of folding element was applied to predict the crushing behavior of the thin-walled tubes under axial impact. The corners on the cross section were discussed to determine their effect on the energy absorption performance of thin-walled tubes. Results showed that the increasing performance of energy absorption of aluminum alloy thin-walled tubes was caused by the increasing number of corners on the cross section of multicorner tubes. Both the number and size of corners had an important effect on the crushing force efficiency of multicorner tubes. The maximum crushing force efficiency of multicorner tubes was 11.6% higher than that of square tubes with the same material consumption of thin-walled tubes. The multicorner tubes with 12 corners showed better energy absorption performance than the tubes with more than 12 corners; this high number of corners could lead to the small size of corners or unstable deformations. The high energy absorption performance of multicorner tubes prefers increasing the corner number and corner size of adjacent sides at the same time.     

The influence of heat treatment on the sliding wear behavior of a ZA-27 alloy

The effects of heat treatment, involving solutionizing at temperature of 370 °C for a relatively short period of time (3 or 5 h), followed by quenching in water, on tribological behavior of ZA-27 alloys were examined.Dry sliding wear tests were conducted on as-cast and heat-treated ZA-27 samples using block-on-disk machine over a wide range of applied loads. To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The tribological results were related to the microstructure and mechanical properties.The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, both from the aspects of friction and wear. The improved tribological behavior of the heat-treated alloys, in spite of reduced hardness, could be the result of breaking the dendrite structure, when the fraction of interdendrite regions was considerably decreased and a very fine α and η mixture was formed at the same time. The wear response of the samples has been corroborated through characteristics of worn surfaces and dominant wear mechanisms.     

Effect of static and dynamic ageing on wear and friction behavior of aluminum 6082 alloy

In the present investigation the effect of static and dynamic ageing on the wear and friction behavior of aluminum alloy (AA 6082) sliding against tool steel (TS) surface has been studied. The AA 6082 alloy samples used in the present study were in as-cast, solutionized and peak aged conditions. Scanning electron microscope analysis of the debris and worn surfaces revealed the role of precipitates on the dry sliding wear behavior. Frictional behavior varies significantly for all the conditions at elevated temperature (180 °C) compared to room temperature (40 °C). Such response was attributed to the dynamic precipitations during elevated temperature test.     

Effects of aging heat treatment on machinability of alumina short fiber reinforced LM 13 aluminum alloy

In this paper, the surface integrity (Ra and Rmax) has been investigated with various aging heat treatment and machinability parameters in an aluminum-silicon based (LM–13) MMCs, produced by infiltration method. The composites have been subjected to heat treatment at different temperatures and times which was discussed in detail in an earlier publication (Altunpak and Akbulut, Teknoloji 8(4):331–339, 2005). In the milling of alumina short fiber reinforced LM–13 aluminum alloys, the surface integrity decreased when feed rate increased. It was found that increasing amount of fiber reinforcement and solutionizing temperature has a significant effect on the surface integrity and sub-surface damage of the materials. Increasing the solutionizing temperature and fiber reinforcement produced higher Ra and Rmax values. Microhardness measurement indicated that the sub-surface damage and the hardness increased by increasing the feed rate and fiber content.     

Dual-rotary fretting wear behavior of 7075 aluminum alloy

Friction and wear behavior of dual-rotary fretting (DRF) combined by torsional and rotational fretting modes have been investigated. Such fretting mode is essentially achieved by changing tilt angles of the rotary axis and varying rotary angular displacement amplitudes The DRF behavior has been characterized from the dynamic behavior, wear damage, third-body behavior, wear mechanisms. The running condition fretting map (RCFM) of DRF fretting wear was established by using the tilt angles and angular displacement amplitudes. The evolution of the wear volume vs the tilt angle under varied angular displacement amplitudes was quantificationally measured. In addition, the competition between the local wear and fatigue (cracking, wear) has been discussed in detail. The results indicated that the damage of 7075 aluminum alloy induced by DRF was strongly dependent upon the tilt angle and the angular displacement amplitude.     

Effect of waterjet peening on aluminum alloy 5005

The present study addresses the effect of waterjet peening parameters on aluminum alloy 5005. The approach was based on the response surface methodology utilizing the Box–Behnken experimental design. Workable empirical models were developed to predict surface roughness (R _a ) and hardness (HV). Increasing the number of passes, pressure, and standoff distance produces a higher surface roughness as well as a higher hardness. On the contrary, increasing the feedrate produces a lower surface roughness and hardness. The developed empirical models for R _a and HV have reasonable correlations between the measured and predicted responses with acceptable coefficients of determinations. A different set of optimum parameters was generated based on different desirability functions for each response. The predicted and the actual responses for optimized R _a and HV are satisfactory with good reliability. It is shown that the models are workable in predicting the responses of R _a and HV in the present research. A proper selection of peening parameters can be formulated to be used in practical works.     

Effect of weld characteristics on the formability of welded tubes in NC bending process

The weld profiles, weld width, weld positions, and mechanical property changes in the weld and heat-affected zones (HAZ) are the most important parameters that influence the potential formability of the welded tube. To investigate the effect of weld characteristics on the forming behaviors of the welded tube, finite element models which consider the geometric profile and mechanical properties of the weld and HAZ are employed. The results show that (1) the mechanical constitutive relation of the weld region determined by the microhardness empirical formula obviously decreases the tangent strain, thickness strain, and cross-sectional deformation ΔD in the weld and HAZ as compared with that determined by the improved rule of mixtures, which is contrary to the hoop strain, and the predicted results determined by the improved rule of mixtures are much closer to the experimental ones; (2) different weld and HAZ widths determined by the microhardness profile and metallographic section have a little effect on the tangent strain, thickness strain, and ΔD distribution; (3) the implementation of weld profile and material properties decreases the wall variation of the weld region as the weld line locates on the outside and inside. On the contrary, both the weld profile and weld material properties increase the maximum ΔD. The sectorial weld profile has a stronger effect on the wall variation and maximum ΔD than the hourglass profile; and (4) the same weld and HAZ volume have a stronger effect on wall thinning and ΔD.     

Densification behavior of aluminum alloy powder under cold compaction

Densification behavior of aluminum alloy (Al6061) powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. A special form of the Cap model was proposed from experimental data of Al6061 powder under triaxial compression. The proposed yield function and several other yield functions in the literature were implemented into a finite element program (ABAQUS) to compare with experimental data for densification behavior of Al6061 powder under cold isostatic pressing and die compaction. The agreement between finite element calculations from the proposed yield function and experimental data is very good under cold isostatic pressing and die compaction.     

铝合金板快速加热弯曲的参数预测

基于BP神经网络平台,建立了铝合金板快速加热弯曲的角度预测BP网络模型,实现了脉冲激光加工工艺的参数控制与优化。通过试验获得样本数据,将试验样本数据用于BP网络的训练,利用训练好的BP网络对非线性的样本数据规律进行拟合,对脉冲激光弯曲角度和工艺参数进行准确的预测,预测误差范围可控制在＜5~8%,研究结果为实际生产中精密成形提供了有效的理论与试验依据。     

Effect of heat treatment on the microstructure and properties of Ni based soft magnetic alloy

A Ni‐based alloy was heat treated by changing the temperature and ambient atmosphere of the heat treatment. Morphology, crystal structure, and physical performance of the Ni‐based alloy were characterized via SEM, XRD, TEM, and PPMS. Results show that due to the heat treatment process, the grain growth of the Ni‐based alloy and the removal of impurities and defects are promoted. Both the orientation and stress caused by rolling are reduced. The permeability and saturation magnetization of the alloy are improved. The hysteresis loss and coercivity are decreased. Higher heat treatment temperature leads to increased improvement of permeability and saturation magnetization. Heat treatment in hydrogen is more conducive to the removal of impurities. At the same temperature, the magnetic performance of the heat‐treated alloy in hydrogen is better than that of an alloy with heat treatment in vacuum. The Ni‐based alloy shows an excellent magnetic performance on 1,373 K heat treatment in hydrogen atmosphere. In this process, the µ_m, B_s, P_u, and H_c of the obtained alloy are 427 mHm^?1, 509 mT, 0.866 Jm^?3, and 0.514 Am^?1, respectively. At the same time, the resistivity of alloy decreases and its thermal conductivity increases in response to heat treatment.     

Effect of hydrogen heat treatment on antifriction properties of nitrided VT6 titanium-based alloy

A comparative study of the antifriction characteristics of specimens of the VT6 titanium-based alloy subjected to nitriding without preliminary treatment and after hydrogen heat treatment has been carried out. Hydrogen heat treatment that precedes nitriding reduces the coefficient of friction of the nitrided specimens of the VT6 alloy in pair with the 12Kh18N10T stainless steel by 4–9% under dry friction and increases it by ~47% in a working fluid, which is a 0.9% NaCl solution. Hydrogen heat treatment combined with ionplasma nitriding reduces the coefficient of friction in working fluid by ~41%.     

Effect of pre-treatment polishing on fabrication of anodic aluminum oxide using commercial aluminum alloy

Aluminum anodizing is a process in which metal is oxidized with an electrochemical method to make a metallic oxide. Because it can be used to manufacture an Anodic aluminum oxide (AAO) with dozens to hundreds of nanoscale pores that are vertically and uniformly arranged, it is widely applied in a variety of fields. In particular, most of the pre-treatment methods in the anodic oxidation processes using a high-purity aluminum adopt surface treatment through electrolyte polishing. In this study, complex polishing was performed using an abrasive film and Magnetorheological (MR) fluid for a commercial aluminum alloy to produce a uniform porous oxidized aluminum. The surface roughness and surface integrity were analyzed after each process to investigate the production behavior of AAO in relation to the pre-treatment of the surface. In addition, a study was conducted on the nano-pore production by the anodizing process in accordance with the pre-treatment polishing, in terms of the work-hardening and residual stress. Thus, in the anodic oxidation process, it was possible to generate uniform nano-pores when surface integrity including surface roughness and residual stress distribution of the aluminum alloys are excellent. Test results showed that the polishing process using the MR fluid did not generate process scratches and pits, but could effectively remove the work-hardening and compressive residual stress, proving that MR fluid polishing method is a suitable pre-treatment process to produce nano-pores in the anodizing process.