Sn-Pb-RE钎料的塑性变形抗力研究

利用拉伸实验方法研究了室温下ＳｎＰｂＲＥ钎料的塑性变形抗力。钎料的变形抗力随稀土含量的增加而提高。稀土的加入使钎料组织均匀细化，导致位垒硬化和多滑移硬化作用增强；同时，稀土存在晶界偏聚，牵制了晶界的运动，因此提高了钎料的变形抗力。此外，由于稀土化合物较硬。

预力学循环对SiCp/2024Al复合材料塑性变形抗力的影响

实验研究了预力学循环对退火及T6处理状态碳化硅颗粒增强铝基复合材料塑性变形抗力的影响。结果表明,两种热处理状态复合材料的预力学循环效果不同。对退火态复合材料,预力学循环对塑性变形抗力的影响主要取决于力学循环应力幅度σa:在较低σa条件下,宏观屈服强度无明显变化,而少数几个循环即可提高微屈服强度,但循环次数再增多,微屈服强度也基本不变;随σa的升高,宏观及微屈服强度均有较明显的增高;但当σa过高时,将会因微结构损伤造成宏观屈服强度和微屈服强度急剧下降,即存在一个最佳的σa,使各级塑性变形抗力达到最高。对T6态复合材料,预力学循环提高塑性变形抗力的效果不佳。

强烈地震下偏心支撑钢框架塑性变形抗力的数值模拟

由于传统偏心支撑钢框架塑性变形抗力数值模拟方法的滞回性能较差,并且不适用于偏心支撑钢框架的塑性变形抗力数值模拟,因此提出一种强烈地震下偏心支撑钢框架塑性变形抗力的数值模方法;利用SATWE软件分析强烈地震时弹性受力状态下的外部荷载状况,并计算其外部荷载控制参数,以获取强烈地震下变形抗力数值模拟中的外部荷载取值;构建一个偏心支撑钢框架有限元模型,模型为一个单斜杆8层3跨的偏心支撑钢框架模型;选取强烈地震波,其中包括人工波1条与自然地震波7条,利用这8条强烈地震波对构建的偏心支撑钢框架有限元模型进行塑性变形抗力数值模拟。为了证明该方法的滞回性能较强,将该方法与传统钢框架塑性变形抗力数值模拟方法进行对比实验,实验结果证明该方法的滞回性能优于传统方法,实现了性能方面的提升。

攀钢09CuPRE等钢种热金属变形抗力的试验研究

介绍了０９ＣｕＰＲＥ，１６Ｍｎ，Ｑ２３５钢在热模拟试验机上完成热金属变形抗力试验的情况。就试验中变形温度、变形速度、变形程度对变形抗力的影响规律，选定了变形抗力计算模型，并通过多元非线性回归数据处理确定模型参数，该模型具有较高的拟合精度。根据模型整理出的图表可供直接查找使用。

Q235钢变形抗力的数学模型

为了准确计算连轧工字钢力能参数,需要建立变形抗力的计算模型。利用Gleeble-1500热模拟试验机对Q235钢的金属塑性变形抗力进行试验研究,通过实测不同变形温度、变形速率、变形程度与变形抗力的关系,建立了金属塑性变形抗力的数学模型。通过对模型进行回归分析,证明该模型具有良好的曲线拟合特性,为计算其他力能参数提供理论计算依据。

涟钢CSP变形抗力模型初探

热轧金属塑性变形抗力的预报精度直接影响到轧制力、温度以及辊缝等模型的预报精度。为准确计算金属塑性变形抗力,提高轧制计算预报精度,对CSP的轧制力预报模型以及控制程序进行了研究,同时收集了多个钢种的实际变形抗力的数据,对不同条件下（化学成分、温度、轧制力、速度）的变形抗力进行了统计分析和回归分析,并对部分钢种的变形抗力模型参数进行了修改和优化,取得了良好效果。

Microstructure and mechanical properties of AZ61 magnesium alloy prepared by repetitive upsetting-extrusion

The process of repetitive upsetting-extrusion （RUE） was used to achieve severe plastic deformation （SPD） for an as-cast AZ61 magnesium alloy in temperature range of 285-380 ℃. The microstructure and mechanical properties of the as-cast and RUE processed AZ61 alloys were investigated. The results indicated that homogeneous fine-grained structure with mean grain size of 3.5 μm was obtained as the accumulated true strain in the axial direction increased to 4.28 after three RUE passes at 285 ℃. The dominant reason of grain refinement was considered the dynamic recrystallization induced by strain localization. It was also found that the microstructural evolution was affected by temperature and accumulated deformation. The mechanical properties of RUE processed AZ61 alloys were significantly improved owing to grain refinement. Furthermore, the relationship between deformation parameters and mechanical properties of AZ61 alloy prepared by RUE processing was revealed by tensile tests carried out at room temperature.

Plastic yielding of NiTi shape memory alloy under local canning compression

As a new attempt, local canning compression was applied in order to implement large plastic deformation of nickel-titanium shape memory alloy （NiTi SMA） at room temperature. The plastic mechanics of local canning compression of NiTi SMA was analyzed according to the slab method as the well as plastic yield criterion. Transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM） and scanning electron microscopy （SEM） were used to study the microstructural evolution as well as deformation behavior of NiTi samples under local canning compression. Increasing the hydrostatic pressure with the increase in the outer diameters of the steel cans is responsible for suppressing the initiation and growth of the micro-cracks, which contributes to enhancing the plasticity ofNiTi SMA and avoiding the occurrence of brittle fracture. Plastic deformation of NiTi SMA under a three-dimensional compressive stress state meets von-Mises yield criterion at the true strains ranging from about 0.15 to 0.50, while in the case of larger plastic strain, von-Mises yield criterion is unable to be met since the amorphous phase arises in the deformed NiTi sample.

Casting effect on compressive brittleness of bulk metallic glass

An interesting phenomenon of cooling-rate induced brittleness in Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） was reported. It was found that the as-cast BMG specimens exhibited a brittle-ductile transition when the larger specimens were machined into smaller specimens through removing the cast-softening surface layer by layer. After compression tests, the as-machined small specimens, owing to the absence of the cast-softening surface, displayed highly dense and intersecting shear bands, and extensive plastic deformation. This is in contrast to the catastrophic failure and low deformability in the as-cast large specimens. More free volume was detected in the smaller as-fractured specimens, by differential scanning calorimetry, which may be attributed to the occurrence of strain softening and increased plasticity. Compared with the relatively smooth fracture surface in the smaller specimens, the larger specimens showed more diverse features on the fracture surface due to their graded structures.

两种热冲压模具用钢的抗拉毛性能

诸多汽车零部件制造商通过表面处理缓解零部件的热冲压拉毛问题,但该处理将提高生产成本。为此,本研究从模具材料合金化配比出发,通过实验和理论研究,初步判断热冲压模具抗拉毛性能与模具材料抵抗塑性变形的能力有关,为验证该猜想,采用透射电子显微镜(TEM)、X射线衍射仪、应力仪、显微维氏硬度计等手段分析了两种模具材料(SDCM钢和SDHS2钢)回火态的碳化物类型、碳化物分布、位错密度、喷丸后的截面残余应力梯度和显微硬度梯度。结果表明:与SDHS2钢相比,抗拉毛性能较优的SDCM钢的屈服强度较高,其在相同的外加应力下,具备更强的塑性变形抗力,变形软化层较浅。此外,热处理后SDCM钢和SDHS2钢中均以钒系碳化物为主,其中高碳高钒低铬的SDCM钢中碳化物的体积分数和位错密度较大,使其具有较高的析出强化和位错强化效果,提高了材料的屈服强度。

DETERMINATION OF PRESSURIZING CURVE AND COMPUTER CONTROL OF THICKNESS THINNING FOR SUPERPLASTIC BULGING

This paper proposes the assumption that the flow with viscous friction is the stretch of part of the sheet that lies along the walls of a die during the process of superplastic bulging according to superplastic flow equation and geometrical model of bulging of a sheet into a long trapezoid groove or truncated cone, by introducing the friction-factor P which describes the friction effect on the process. Also, the paper proposes the method of controlling thickness nonuniformity and develops the equipment which for uniform thickness of bulging, is automatically controlled with a computerl it also analyzes the important innuence of lubrication on thickness distribution of bulging materials. By the assumption, the relationship between bulging pressure and time is obtained in bulging of a sheet into the groove and cone, and p-t curve of multi-mould-cavity complicated bulging is discussed based on the analysis of single-mould-cavity bulging characteristics.

Flow stress behavior and processing map of extruded 7075Al/SiC particle reinforced composite prepared by spray deposition during hot compression

Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.

Effect of heat treatment on microstructure and dimensional stability of ZL114A aluminum alloy

The effects of heat treatment process on microstrucature, micro-yield strength and dynamic dimensional stability of ZL114A aluminum alloy were investigated by optical microscopy （OM）, transmission electron microscopy （TEM）, tensile testing and thermal cycling on-line measuring method. Fine dispersed eutectic Si phases are observed, and long strip eutectic Si and massive primary Si phases decrease in ZL114A alloy after high-temperature and long-time solution treatment, which result in the increase of micro-plastic deformation resistance. With the increasing of aging temperature, aging precipitation behaviour of ZLll4A alloy transforms from precipitation of GP zone and fl＇ phases simultaneously at lower temperature to precipitation of stable Mg2Si phases at higher temperature. Because coherent strengthening is the main strengthen mechanism for micro-plastic deformation, precipitation of stable Mg2Si phases is unfavorable to the improvement of micro-plastic deformation resistance. Micro-yield strength cannot characterize dimensional stability comprehensively, and dynamic dimensional stability under alternative temperature should also be tested cooperatively for better evaluation of dimensional stability.

Plastic deformation behavior of Mg97Zn1Y2 extruded alloys

The mechanical properties of the Mg97ZnlY2 extruded alloy containing the long-period stacking ordered phase, the so-called LPSO-phase, with a volume fraction of 24%-25%, were examined by compression tests and cyclic tension-compression deformation tests. The plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2Y0.6 and Mg89Zn4Y7 （molar fraction, %）, which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1Y2 Mg/LPSO two-phase alloy, respectively, were also prepared. By comparing their mechanical properties, the strengthening mechanisms operating in the Mg97Zn1 Y2 extruded alloy were discussed. Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion, which led to a large increment of the strength of alloy. In addition, the LPSO-phases, which were aligned along the extrusion direction in Mg97Zn1Y2 extruded alloy, acted as hardening phases, just like reinforced fibers.

Structure,strength and superplasticity of ultrafine-grained 1570C aluminum alloy subjected to different thermomechanical processing routes based on severe plastic deformation

A comparative study of the structure and mechanical behavior of an Al-5 Mg-0.18 Mn-0.2 Sc-0.08 Zr-0.01 Fe-0.01 Si(wt.%)alloy ingot subjected to multidirectional isothermal forging(MIF)to a strain of 12 or equal-channel angular pressing(ECAP)to a strain of 10 at 325℃,and subsequent warm and cold rolling(WR and CR)at 325 and 20℃,was performed.The results showed that the MIF process of ultrafine-grained structure with a(sub)grain size dUFG=2μm resulted in enhanced room-temperature ductility and superplastic elongation up to 2800%.Further grain refinement under WR as well as development of a heavily-deformed microstructure with high dislocation density by subsequent CR resulted in a yield/ultimate tensile strength increase from 235/360 MPa after MIF to 315/460 and 400/515 MPa after WR and CR,respectively.Simultaneously,WR led to improved superplastic elongation up to 4000%,while after CR the elongation remained sufficiently high(up to 1500%).Compared with MIF,ECAP resulted in more profound grain refinement(dUFG=1μm),which promoted higher strength and superplastic properties.However,this effect smoothed down upon WR,ensuring equal properties of the processed sheets.CR of the ECAPed alloy,in contrast,led to higher strengthening and slightly better superplastic behavior than those after CR following MIF.

Mechanical behavior and deformation mechanism of ballast bed with various fouling materials

In order to study the interaction between various fouling particles and ballast,a multi-layer and multi-scale discrete element model(DEM)including the sleeper,ballast bed and the surface layer of subgrade was developed.Two typical fouling particles,the hard particles(sand)and soft ones(coal fines),are considered.A support stiffness test of the ballast bed under various fouling conditions was conducted to calibrate the microscopic parameters of the contact model.With the model,the influence of fouling particles on the mechanical behavior and deformation of the ballast bed was analyzed from macro and micro perspectives.The results show that the increase in the strength of the fouling particles enlarges the stiffness of the ballast bed.Hard particles increase the uniformity coefficient of the contact force bondγof ballast by 50.4%.Fouling particles increase the average stress in the subgrade,soft particles by 2 kPa and hard particles by 1 kPa.Hard particles can reduce the elasticity,plastic deformation and energy dissipation in the track structure.As the fouling particle changes from hard to soft,the proportion of the settlement in ballast bed increases to 40.5%and surface layer of swbgrade settlement decreases to 59.5%.Thus,the influence of fouling particles should be considered carefully in railway design and maintenance.

锆合金的切削加工

我公司根据市场需求开发了锆材泵阀产品.主要涉及的是锆合金：Zr702铸件和Zr705棒料锻件.锆对多种酸（如盐酸、硝酸、硫酸和醋酸）、碱和盐具有优良的抗蚀性,锆合金在300 ～ 400℃的高温高压水和蒸汽中具有良好的耐蚀性能.1.锆合金的切削特点（1）切削力大.锆合金的强度和硬度较高,塑性变形抗力大,且冷硬现象较严重,所以切削力很大.同时,锆合金在空气中易形成氧化层,氧化表层的强度和硬度更高,因此单位面积承受的切削力更大.

Effects of non-isothermal annealing on microstructure and mechanical properties of severely deformed 2024 aluminum alloy

Microstructure and mechanical properties of AA2024 after severe plastic deformation （SPD） and non-isothermal annealing were investigated. The non-isothermal treatment was carried out on the severely deformed AA2024, and the interaction between restoration and precipitation phenomena was investigated. Differential scanning calorimetry, hardness and shear punch tests illustrate that static recovery and dissolution of GPB zones/Cu-Mg co-clusters occur concurrently through non-isothermal annealing. Scanning electron microscope and electron backscatter diffraction illustrate that non-isothermal annealing of deformed AA2024 up to 250 ℃ promotes the particle-free regions and also particle stimulated nucleation. Results show that through heating with the rate of 10 ℃/min up to 250 ℃, the ultimate shear strength and the hardness are maximum due to the presence of S＇/S phases which have been detected during non-isothermal differential scanning calorimetry experiment. Also, recrystallization phenomenon occurs in temperature range which includes the dissolution of S＇/S phases. The concurrent recrystallization and dissolution of S＇/S phase at 380 ℃ have been verified by differential scanning calorimetry, mechanical properties, and optical microscope.

Processing and characterization of AZ91 magnesium alloys via a novel severe plastic deformation method:Hydrostatic cyclic extrusion compression(HCEC)

Capability of a novel severe plastic deformation(SPD)method of hydrostatic cyclic extrusion compression(HCEC)for processing of hcp metallic rods with high length to diameter ratios was investigated.The process was conducted in two consecutive cycles on the AZ91 magnesium alloy,and microstructural evolution,mechanical properties and corrosion behavior were investigated.The results showed that the HCEC process was successively capable of producing ultrafine-grained long magnesium rods.Its ability in improving strength and ductility simultaneously was also shown.The ultimate tensile strength and elongation to failure of the sample after the second cycle of the process were improved to be 2.46 and 3.8 times those of the as-cast specimen,respectively.Distribution of the microhardness after the second cycle was uniform and its average value was increased by 116%.The potentials derived from the polarization curves were high and the currents were much low for the processed samples.Also,the diameter of the capacitive arcs derived from the Nyquist curves was large in the HCEC processed samples.The finite element analysis indicated the independency of HCEC load from the length in comparison to the conventional CEC.HCEC is a unique SPD method,which can produce long ultrafine-grained rods with a combination of superior mechanical and corrosion properties.