Microstructural Evolution and Biodegradation Response of Mg–2Zn–0.5Nd Alloy During Tensile and Compressive Deformation

The effect of deformation behavior on the in vitro corrosion rate of Mg–2Zn–0.5 Nd alloy was investigated experimentally after uniaxial tensile and compressive stress. The microstructure and texture were characterized using electron backscattered diffraction and X-ray diffraction, while potentiodynamic polarization and immersion tests were used to investigate the corrosion response after deformation. The result reveals that applied compressive stress has more dominant effect on the corrosion rate of Mg–2 Zn–0.5 Nd alloy as compared to tensile stress. Both tensile and compressive strains introduce dislocation slip and deformation twins in the alloy, thereby accelerating the corrosion rate due to the increased stress corrosion related to dislocation slips and deformation twins. The {10ī2} tension twinning and prismatic slip were the major contributors to tensile deformation while basal slip, and {10ī2} tension twin were obtainable during compressive deformation. The twinning activity after deformation increases with the plastic strain and this correlates with the degradation rate.     

Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process

Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y_1 Zn_(0.5) alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y_1 Zn_(0.5) alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.     

Enhanced Strength and Corrosion Resistance of Mg–2Zn–0.6Zr Alloy with Extrusion

The microstructure, mechanical properties and corrosion behavior of Mg–2 Zn–0.6 Zr alloy under the as-cast and asextruded conditions were investigated. Microstructure analysis indicated the remarkable grain refinement by extrusion, as well as notable reductions in volume fraction and size of precipitate phases. As compared with the as-cast alloy, the asextruded alloy exhibited better mechanical performance, especially in yield strength which was promoted from 51 to 194 MPa. Refined grains, dispersive precipitate phases and texture were thought to be the main factors affecting the improved performance in strength. The electrochemical measurement and immersion test revealed the corrosion rate of Mg–2 Zn–0.6 Zr alloy by extrusion decreased from 1.68 to 0.32 mm/year. The reasons for the enhanced corrosion resistance were mainly attributed to the decreased volume fraction and Volta potential of the precipitate phases, the refinement of the grain size, as well as the formation of more protective corrosion film.     

Obtaining Ultra-High Strength and Ductility in a Mg–Gd–Er–Zn–Zr Alloy via Extrusion,Pre-deformation and Two-Stage Aging

The Mg–12Gd–1Er–1Zn–0.9 Zr(wt%) alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging treatment.The age-hardening behavior and microstructure evolution were investigated.Pre-deformation introduced a large number of dislocations,resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage aging.As a result,the alloy showed a superior strength–ductility balance with a yield strength of 506 MPa,an ultimate tensile strength of 549 MPa and an elongation of 8.2% at room temperature.The finer and denser β' precipitates significantly enhanced the strength,and the bimodal structure,small β-Mg_5RE phase as well as dense γ' precipitates ensured the good ductility of the alloy.It is suggested that the combination of pre-deformation and two-stage aging treatment is an eff ective method to further improve the mechanical properties of wrought Mg alloys.     

Influence of Zn Content on Microstructure and Tensile Properties of Mg–Zn–Y–Nd Alloy

In the present study, the effect of Zn content on the microstructure and deformation behavior of the as-cast Mg–Zn–Y–Nd alloy has been investigated. The results showed that as Zn content increased, the volume fraction of secondary phases increased. Moreover, the phase transformation from W-phase to W-phase and I-phase occurred. In the as-cast state,W-phase exists as eutectic and large block form. When Zn content increases to 6 and 8%(wt%), small I-phase could precipitate around W-phase particles. Additionally, the effect of Zn content on the tensile properties and deformation behavior varies with the testing temperature. At room temperature, the tensile strength increases with Zn content, whereas the elongation increases initially and then decreases. At 250 °C, as Zn content increases, the tensile strength decreases initially and then increases slightly, whereas the elongation decreases. At 350 °C, the elongation increases with Zn content,whereas the tensile strength decreases initially and then increases slightly.     

A High-Strength and Biodegradable Zn–Mg Alloy with Refined Ternary Eutectic Structure Processed by ECAP

In this study, the microstructure, mechanical properties and corrosion behaviors of a Zn–1.6 Mg(wt%) alloy during multipass rotary die equal channel angle pressing(RD-ECAP) processing at 150 °C were systematically investigated. The results indicated that a Zn + Mg_2 Zn_(11) + MgZn_2 ternary eutectic structure was formed in as-cast Zn–Mg alloy. After ECAP, the primary Zn matrix turned to fine dynamic recrystallization(DRX) grains, and the network-shaped eutectic structure was crushed into fine particles and blended with DRX grains. Owing to the refined microstructure, dispersed eutectic structure and dynamically precipitated precipitates, the 8 p-ECAP alloy possessed the optimal mechanical properties with ultimate tensile strength of 474 MPa and elongation of 7%. Moreover, the electrochemical results showed that the ECAP alloys exhibited similar corrosion rates with that of as-cast alloys in simulated body fluid, which suggests that a high-strength Zn–Mg alloy was successfully developed without sacrifice of the corrosion resistance.     

Dislocation-Induced Precipitation and Its Strengthening of Al–Cu–Li–Mg Alloys with High Mg

Generally, the good combination of pre-deformation and aging can improve the mechanical strength of the Al–Cu–Li–Mg alloys. However, the effects of pre-deformation on competitive precipitation relationship and precipitation strengthening have not been clarified in detail in Al–Cu–Li–Mg alloys with high Mg. In the present study, the effects of pre-deformation level on the microstructure and mechanical properties of an Al–2.95 Cu–1.55 Li–0.57 Mg–0.18 Zr alloy have been investigated. It is found that the introduction of dislocation by 5% pre-deformation can facilitate the precipitation of new successive composite precipitates and T _1 precipitates along the sub-grain boundaries or dislocations and inhibit the precipitation of dispersive GPB zones which is the main precipitates of the alloys without pre-deformation. The introduction of 5% pre-deformation can enhance the mechanical properties considerably. When the pre-deformation level increases from 5 to 15%, the number density of the successive composite precipitates and T _1 precipitates increases, and the aspect ratio of T _1 precipitates decreases. The decrease in T _1 precipitate aspect ratio and the increment of the successive composite precipitates result in the reduction in precipitation strengthening. Therefore, the increase in pre-deformation level from 5 to 15% does not further improve the mechanical properties of the alloys, although the dislocation strengthening increases continuously.     

Strength Prediction of Aluminum–Stainless Steel-Pulsed TIG Welding–Brazing Joints with RSM and ANN

Pulsed TIG welding–brazing process was applied to join aluminum with stainless steel dissimilar metals. Major parameters that affect the joint property significantly were identified as pulsed peak current, base current, pulse on time,and frequency by pre-experiments. A sample was established according to central composite design. Based on the sample,response surface methodology(RSM) and artificial neural networks(ANN) were employed to predict the tensile strength of the joints separately. With RSM, a significant and rational mathematical model was established to predict the joint strength.With ANN, a modified back-propagation algorithm consisting of one input layer with four neurons, one hidden layer with eight neurons, and one output layer with one neuron was trained for predicting the strength. Compared with RSM, average relative prediction error of ANN was \10% and it obtained more stable and precise results.     

Anti-Corrosion and Tribo-Mechanical Properties of Co-deposited Zn–SnO_2 Composite Coating

Zn–Sn O2 composite coatings were prepared by direct potential using electrolytic co-deposition technique from sulfate solution.The effect of Zn2?and Sn O2 concentrations in deposited bath on the mechanical properties and morphological characteristics of the composite coatings were examined.The characterizations of the sample were analyzed using scanning electron microscopy couple with energy dispersive spectroscopy(SEM/EDS),X-ray diffraction(XRD) and atomic force microscopy(AFM).The electrochemical degradation behavior of the samples in 3.65 wt.% Na Cl solution was studied using potentiodynamic polarization technique and characterized by high-resolution optical microscope.From all the fabricated composite coatings,obvious diffraction peaks were observed with Zn-7Sn-S-0.3V film with Zn2Sn7,Sn,Zn2Sn5 and Zn phases,confirming the presence and formation of Zn–Sn O2 coating.The XRD pattern shows that the presences of Sn O2 particle remarkably play a major role in the precipitation and orientation of the alloy matrix.From the SEM/EDS and AFM results,the deposits show that composite particle and proper bath composition have strong influence on the microstructure.An enhanced corrosion resistance was attained as a result of the induced particles.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

基于响应曲面法的表面粗糙度预测模型研究

分析以往建立表面粗糙度预测模型方法的不足,采用响应曲面法（RSM）建立了钢及其合金铣削加工表面粗糙度预测模型。经检验,该模型预测精度高,泛化能力强,且可简便预测铣削参数对已加工表面的表面粗糙度的影响,有助于准确认识已加工表面质量随铣削参数的变化规律,为切削参数的优选和表面质量的控制提供了依据。     

Quantitative Modeling for Corrosion Behavior in Complex Coupled Environment by Response Surface Methodology

Response surface methodology(RSM) is introduced into corrosion research as a tool to assess the effects of environmental factors and their interactions on corrosion behavior and establish a model for corrosion prediction in complex coupled environment(CCE). In this study, a typical CCE, that is, the corrosion environment of pipelines in gas field is taken as an example. The effects of environmental factors such as chloride concentration, pH value and pressure as well as their interactions on critical pitting temperature(CPT) were evaluated, and a quadratic polynomial model was developed for corrosion prediction by RSM. The results showed that the model was excellent in corrosion prediction with R2= 0.9949. CPT was mostly affected by single environmental factor rather than interaction, and among the whole factors, chloride concentration was the most influential factor of CPT.     

响应面法优化空气喷嘴雾化流场的数值研究

为提高空气喷嘴的喷涂性能,采用计算流体力学对空气喷嘴与喷涂面之间的雾化流场进行数值模拟,并结合响应面法对喷嘴的结构参数与工况参数进行总体优化.首先搭建热线风速仪测速实验台验证数值计算模型的准确性,然后设计三因素的中心复合试验,建立以塑形气孔斜面倾角α、环形气孔压力p1、塑形气孔压力p2为设计变量,以喷涂面中心压力pc为...     

钛合金抛光表面粗糙度与表面形貌研究

为了优化钛合金抛光工艺参数,采用中心复合响应曲面法,建立了抛光表面粗糙度的预测模型;采用方差分析方法,检验了预测模型以及各抛光参数的显著性,分析了各抛光参数对表面粗糙度及表面形貌的影响规律。结果表明:该预测模型可对抛光表面粗糙度进行有效的预测;页轮粒度、页轮线速度和进给速度对表面粗糙度影响极显著;表面粗糙度随页轮粒度、页轮线速度和进给速度的增大而减小;表面形貌整体均匀,存在一定的隆起和沟壑。     

Zn对粉末冶金法制备Mg-Zn合金组织与性能的影响

以Mg粉和Zn粉为初始原料,采用粉末冶金技术制备Mg-Zn合金。研究了Zn含量对Mg-Zn合金烧结密度、显微组织、物相组成、弯曲强度和显微硬度的影响。测量了Mg-Zn合金的耐腐蚀性,探讨了Zn元素在粉末冶金过程中的作用机理。研究结果表明当添加Zn元素后,烧结产物的晶粒细小,烧结密度提高。此外,随着Zn含量的增加,烧结产物的致密度持续增加。XRD分析表明Mg-3 wt%Zn合金主要由α-Mg相组成,而Mg-4 wt%Zn合金由α-Mg 和 MgZn₂两相组成。随着Zn含量的增加,Mg-Zn合金的弯曲强度先增加而后降低,但是显微硬度持续增加。Mg-3 wt% Zn合金的抗弯强度为123.6 MPa,显微硬度为101.7 HV,分别为纯Mg样品高出58%和45%。耐腐蚀性能测试表明当添加Zn元素后,Mg-Zn合金的腐蚀速率降低,Mg-3 wt%Zn合金具有最低的腐蚀速率和最佳的耐腐蚀性能。     

A Comparative Study of Artificial Neural Network and Response Surface Methodology for Optimization of Friction Welding of Incoloy 800 H

This article deals with the optimization of process parameters for friction welding of Incoloy 800 H rod and compares the results obtained by response surface methodology(RSM) and artificial neural network(ANN).The experiments were carried out on the basis of a five-level,four-variable central composite design.The output parameters were the tensile strength and burn-off length(BOL).They were considered as a function of four independent input variables,namely heating pressure(HP),heating time,upsetting pressure(UP),and upsetting time.The RSM results showed that the quadratic polynomial model depicted the interconnection between individual element and response.For optimizing the process parameters,ANN analysis was used,and the optimal configuration of the ANN model was found to be 4–9–2.For modeling aspect,a requisite trained multilayer perceptron neural network was rooted,and a quick propagation training algorithm was used to train ANN.The purpose of optimization was to decide the maximum tensile strength and minimum burn-off length of the welded joint which was done by varying the friction welding process variables.The order of importance of input parameters for friction welding of Incoloy 800 H was HP [ UP [ N [ BOL.After predicting the model using RSM and ANN,a comparison was made for predicting the effectiveness of two methodologies.By analyzing the results,it was observed that as compared to RSM,ANN model was more specific.     

响应曲面法优化水溶液氯化溶解纯铑粉

利用响应曲面法中心组合设计(CCD)对水溶液氯化溶解纯铑粉的工艺参数进行优化,分别选取反应温度、酸度、时间、氧化剂用量四个主要影响因子,模拟得到二次多项式回归方程的预测模型。结果表明,铑的溶解率影响因子的显著顺序为:温度>时间>酸度>氧化剂用量,优化后的工艺条件为:反应温度90 min,温度90℃,氧化剂/铑粉质量比6.25,酸度8.7 mol/L,铑粉溶解率的预测值为97.13%,实际值为96.58%,响应曲面法优化模型准确有效。     

基于响应曲面法的Ar-N2 等离子射流特性研究

目的研究等离子射流特性,提高射流品质,为工程实践提供支撑。方法通过响应曲面法,以粒子速度和温度为指标反映射流特性的变化,采用Box-Behnken-Design(BBD)设计分析电流(I)、主气流量(Q)以及次级气比例(C)对于射流特性的影响规律及其相互作用关系。结果对粒子速度的影响因素排序为Q_(Ar)IC,对粒子温度的影响因素排序为IQ_(Ar)C。该喷嘴下实现最佳加热效应的参数为:主气流量80 L/min、电流450 A、次级气比例22.5%。实现射流最佳加速效应的离子气及电参数为:主气流量140 L/min、次级气比例15%、电流400 A。在射流最佳加速效应对应参数下制备的AT40涂层均匀致密、孔隙少。结论运用响应曲面法分析和解决等离子射流特性影响问题具有科学性和可操作性,能够有效指导涂层制备。     

基于响应面法的铁表面PTFE涂层的使用寿命研究

目的模拟生活中不粘锅的使用环境,采用响应面法预测铁表面PTFE涂层的使用寿命,为生活中合理使用不粘锅提供支撑。方法通过响应面法考察转速和载荷对铁表面PTFE涂层使用寿命的影响,采用中心组合试验设计(CCD)考察载荷以及转速对于铁表面PTFE涂层使用寿命的影响及其相互作用。结果载荷和转速对于涂层使用寿命的影响都极为显著,检验值(F)都小于0.0001。通过试验设计软件得出使用寿命与转速和载荷的二阶多项式方程,并且复相关系数R2为0.9951,能解释99.51%响应值的变化,因此模型能够较准确地预测铁表面PTFE涂层的使用寿命。该实验工况下铁表面PTFE涂层的最佳使用参数分别为转速200r/min和载荷25 N,此时涂层寿命为147 min左右。结论模拟日常生活中使用不粘锅的实际情况,并运用响应面法分析和预测PTFE涂层的使用寿命具有科学性和可操作性,能够很好地指导生活中安全使用不粘锅。     

基于响应面法的金属打包机箱体结构轻量化设计

金属打包机是废旧金属回收行业的大型核心工程设备.为了提高金属打包机箱体结构的综合性能以及实现箱体轻量化的目标,提出一种基于响应面法的轻量化设计方法.基于板壳理论和力学模型分析建立危险工况的有限元参数化模型,以墙板厚度等尺寸作为设计变量,以结构强度、刚度和稳定性作为约束条件,并以箱体质量作为目标函数.通过灵敏度分析确定对...