冷轧和退火对纯镍拼焊接头组织和力学性能的影响

对纯镍板拼焊接头进行冷轧,然后进行800～1100℃退火,通过对比分析,研究了冷轧和退火工艺对纯镍板材的组织和力学性能的影响。结果表明,经过75%变形量的冷轧加工后,拼焊接头的晶粒破碎,微观组织沿轧制方向呈线性纤维状,其抗拉强度约611 MPa,伸长率约5.6%。在800℃退火时,显微组织发生部分再结晶,但仍然存在大量拉长的线性纤维组织,抗拉强度为387.9 MPa,伸长率为20.4%;在900℃退火时,大部分线性纤维组织发生再结晶,抗拉强度为363.5 MPa,伸长率为23.7%;1000℃退火时,冷轧形成的线性纤维组织完全消失,微观组织发生完全再结晶,抗拉强度为357.5 MPa,伸长率为32.3%;在1100℃退火时,与1000℃退火时相比,微观组织变化不明显,力学性能也无明显变化,抗拉强度为355.3 MPa,伸长率为30.9%。由力学性能和微观组织综合比较可知,1000℃为最佳的中间退火温度。     

退火温度对冷轧商业纯钛板材组织和力学性能的影响（英文）

传统的商业纯钛(CP-Ti)合金强度往往不能满足结构材料的需求。为了提高其力学性能,对冷轧CP-Ti合金在不同温度下退火,并详细研究其再结晶行为和织构演变。结果表明,部分再结晶形成的双态结构(等轴和拉长的晶粒)表现出极限抗拉强度(702MPa)和总伸长率(36.4%)的优异结合。CP-Ti板材的再结晶形核优先发生在高应变和大角度晶界区域。同时,变形不均匀晶粒的内部取向差增大并转变成大角度晶界,进一步促进再结晶形核。主要再结晶织构是由冷轧基面RD-分裂织构转变而来的基面TD-分裂织构,再结晶过程中定向形核起主导作用。     

纯钛再结晶退火的组织演变和力学性能

对纯钛进行650℃×(10～90) min的再结晶等温退火处理.研究发现:保温开始阶段,晶粒尺寸增长速率较慢,由于热轧态下纯钛不同晶粒间晶格畸变能的较大差异,出现了晶粒竞争生长现象,保温初期晶粒尺寸差异明显,一些大晶粒内出现孪晶;在随后的加热过程中,由于晶体内高晶格畸变能,并伴孪生切变,晶粒生长过程中原子扩散速率逐步提高,晶粒增长速率增加,晶粒尺寸趋于均匀;保温60 min后晶粒增长速率降低.随再结晶等温时间延长,材料抗拉强度、屈服强度及硬度逐渐降低,塑性提高.屈服强度与晶粒尺寸符合Hall-petch公式σ-s=310+ 1167 d-1/2.     

工艺因素对连铸轧坯冷轧纯铝薄板组织性能的影响

阐述了冷轧及热处理工艺因素对连续铸轧供坯的纯铝薄板组织及力学性能的影响规律,探讨提高其深冲性 能的可能性。     

退火温度对超细晶工业纯钛组织和力学性能的影响

采用等通道转角挤压对工业纯钛进行加工,获得了超细晶工业纯钛,并对超细晶工业纯钛在不同温度下进行短时退火,研究了退火温度对超细晶工业纯钛组织和力学性能的影响,研究表明,超细晶工业纯钛经300～400℃低温短时退火后,晶粒尺寸没有明显增大,基面织构增强,强度得到提升,产生退火强化现象,且保持良好塑性。随着退火温度提高,超细晶工业纯钛晶粒发生明显长大,强度逐渐下降。     

冷轧退火工艺对铝镁合金组织性能的影响

以半连续铸造Al-4.2Mg合金为对象,研究了冷轧退火处理工艺对其微观组织和力学性能的影响。结果表明,在冷轧过程中,随着压下率的增大,冷轧板材的抗拉强度和屈服强度逐渐提高,伸长率逐渐下降。冷轧板在经过320℃退火保温l h后,抗拉强度达到220 MPa,屈服强度达到80 MPa,伸长率达到30%。     

退火温度对TA1冷轧钛板组织与性能的影响

研究退火温度(550~710℃)对厚度0.5和1.0 mm的TA1冷轧钛板的显微组织及力学性能的影响,结果表明,当退火温度较高时,力学性能受退火温度变化影响较小;应将显微组织和晶粒大小作为重点因素来确定退火工艺;对于0.5 mm、1.0 mm的TA1冷轧钛板,适宜退火温度应分别控制在630~670℃、610~650℃。     

退火对表面机械研磨处理纳米化工业纯钛性能的影响

通过表面机械研磨处理(SMAT)在工业纯钛表面制备出具有纳米晶体特征的表面层,并对其进行不同温度的退火,利用光镜、分层显微硬度测试和极化曲线测量等手段,分别研究了机械研磨处理对工业纯钛和不同退火温度对表面机械研磨处理纳米化工业纯钛性能的影响.结果表明,表面纳米化使工业纯钛在0.5 mol/L H2SO4溶液中的耐腐蚀性变差,而低温退火可改善SMAT处理工业纯钛在0.5mol/L H2SO4溶液中的耐腐蚀性能.工业纯钛经表面纳米化+低温退火处理,可以提高其表面的硬度和耐腐蚀性能.     

冷轧加工对工业纯钛板焊缝组织与性能的影响

采用等离子弧焊将两张3.5 mm厚纯钛板对焊,然后在1 780 mm冷轧机上依次进行变形量为43%、50%的冷轧加工,且冷轧后均进行退火处理。对两个轧程的冷轧态及退火态焊缝试样进行了金相显微组织观察;对两个轧程退火态试样进行了室温力学性能及硬度测试;对退火态成品母材区和焊缝加工区进行了杯突试验和在3.5%NaCl水溶液中的阳极极化试验。结果表明,两次冷变形板材退火后焊缝加工区晶粒尺寸均比母材区略微细小,强塑性略好一些,维氏显微硬度也稍高一些;成品板材焊缝加工区的延伸率与母材相差不大,杯突值相近,具有与母材相当的工艺性能;成品板材焊缝加工区的阳极极化行为与母材无明显差异,二者在3.5%NaCl水溶液中的耐腐蚀性基本一致。     

冷轧对新型Ni-W-Co-Ta高密度合金组织与性能的

在室温环境中对新型Ni-W-Co-Ta高密度合金进行冷轧变形,借助金相显微镜、扫描电镜、透射电镜、X射线衍射仪、背散射电子衍射、电子万能试验机及显微硬度计对新型Ni-W-Co-Ta高密度合金变形过程中的微观组织及力学性能演变规律进行表征。结果表明：随着变形量的增加,新型Ni-W-Co-Ta高密度合金等轴晶粒沿轧制方向不断被拉长,同时产生大量的滑移带协调剧烈的塑性变形,并最终形成纤维组织。变形量的增大导致位错密度急剧增加,位错交互作用显著加强,进而将晶粒尺寸细化至25.5 nm。经过90%的严重塑性变形后,抗拉强度提高到1953 MPa;屈服强度提升至1806 MPa,硬度增加至534 HV,伸长率则急剧下降至9.1%。断口形貌则由韧性断裂向韧性-准解理混合型断裂转变。     

退火工艺对冷轧工业纯钛带卷各向异性的影响

力学性能各向异性是影响工业纯钛板带材成形性能的主要因素之一。为制备低各向异性工业纯钛带卷,采用室温拉伸试验和电子背散射衍射技术表征了经不同工艺退火后冷轧工业纯钛的力学性能、显微组织和织构,分析了退火工艺对工业纯钛带卷力学性能各向异性的影响规律。结果表明,退火温度固定时,延长退火时间,TA1钛带纵向屈服强度降低程度大于横向,导致其各向异性升高,而退火超过一定时间后其各向异性趋于稳定,700 ℃时钛带纵横向屈服强度差值的稳定值为82 MPa,610 ℃时的稳定值为58 MPa;退火时间固定时,在所研究温度范围内,退火温度越高,钛带各向异性越显著。织构分析表明,延长退火时间或/和升高退火温度,TA1钛带的棱锥织构增强、基面织构减弱,导致室温拉伸时纵横向{1010}<1120>柱面滑移的施密特因子差值增大,从而表现出更明显的力学性能各向异性。     

工业纯钛光纤激光-MIG复合焊接工艺及性能

采用光纤激光与熔化极惰性气体保护电弧焊(MIG焊)复合焊接工业纯钛,分别对激光焊、MIG焊和复合焊接头的焊缝表面成形、横断面进行了观察,并进行了激光焊和复合焊接头的拉伸试验及杯突试验.结果表明,复合焊的电弧稳定性比MIG焊显著提高,焊接速度可提高7倍;复合焊与激光焊接头的抗拉强度高于母材;复合焊接头的杯突值优于激光焊接头的杯突值,这是因为复合焊焊缝的微观组织有利于接头的塑性.因此,采用光纤激光-MIG电弧复合焊接方法很好地实现了工业纯钛的高速焊接,焊缝成形良好,接头的塑性优于单一激光焊的塑性.

Abstract：

Fiber laser-metal inert gas (MIG) arc hybrid welding was used to weld the commercial pure titanium (CP-Ti). The weld appearance, cross section, tensile strength, Erichsen value and microstructure of the CP-Ti welded joints were studied. The results show that the arc stability is substantially improved and the welding speed can be increased to 7 times by fiber laser-MIG hybrid welding. The welded joints by laser welding and the hybrid welding exhibit the higher ultimate tensile strength than those of the base metal. In addition, the welded joint by the fiber laser-MIG hybrid welding has higher Erichsen values than that by laser joints. The difference in plasticity is attributed to the microstructure changes in the welded joint of hybrid welding. Thus, the fiber laser-MIG hybrid welding of CP-Ti can be carried out suecessfully at higher welding speed with a good combination of weld bead appearance and plasticity.     

Effect of brazing parameters on microstructure and mechanical properties of titanium joints

This study investigates the influences of brazing temperature and time on microstructures and mechanical properties of commercially pure (CP) titanium. Bonding was performed in a high-vacuum furnace using Incusil-ABA (Ag–27.2Cu–12.5In–1.25Ti, wt.%), as filler metal. Brazing temperatures employed in this study were 710, 750, and 800 °C. At the same time, the investigated holding times at the brazing temperatures were 5, 30, and 90 min. Microstructure and phase constitution of the bonded joints were analyzed by means of metallography, scanning electron microscope (SEM) and X-ray diffraction pattern (XRD). An intense diffusion of Ti to the interface and a strong reaction between the braze alloy and the base metal were observed especially at a temperature of 800 °C. A number of intermetallic phases such as TiCu, Ti₂Cu, Ti₃In, Cu–In, and TiAg have been identified. Both brazing temperature and holding time are critical factors to control the microstructure and hence the mechanical properties of the brazed joints. The optimum brazing parameter was achieved at a temperature of 750 °C and a holding time of 90 min.     

Transformation mechanism and mechanical properties of commercially pure titanium

In order to establish the rolling process parameters of grade-2 commercially pure titanium(CP-Ti),it is necessary to understand the transformation mechanism and mechanical properties of this material.The β→α transformation kinetics of the grade-2 CP-Ti during continuous cooling was measured and its hot compression behavior was investigated using Gleeble-1500 thermal mechanical simulator.Dynamic CCT diagram confirms that cooling rate has an obvious effect on the start and finishing transformation and microstructures at room temperature.The critical cooling rate for β-phase transforms to α phase is about 15 °C/s.When the cooling rate is higher than 15 °C/s,some β phases with fine granular shape remain residually into plate-like structure.The plate-like α phase forms at cooling rate lower than 2 °C/s,serrate α phase forms at medium cooling rates,about 5-15 °C/s.The flow stress behavior of grade-2 CP-Ti was investigated in a temperature range of 700-900 °C and strain rate of 3.6-40 mm/min.The results show that dynamic recrystallization,dynamic recovery and work-hardening obviously occur during hot deformation.Constitutive equation of grade-2 CP-Ti was established by analyzing the relationship of the deformation temperature,strain rate,deformation degree and deformation resistance.     

Static mechanical properties and ductility of biomedical ultrafine-grained commercially pure titanium produced by ECAP process

Equal channel angular pressing (ECAP) is one of the most effective processes to produce ultra-fine grain (UFG) and nanocrystalline (NC) materials. Because the commercially pure titanium exhibits excellent biocompatibility properties, it has a significant potential to be utilized as an implant material. The low static and dynamic strengths of the pure titanium are one of the weaknesses of this material. This defect can be removed by applying the ECAP process on the pure titanium. In this work, the commercially pure titanium Grade 2 (CP-Ti of Grade 2) was pressed at room temperature by the ECAP process via a channel angle of 135° for 3 passes. The microstructural analysis and mechanical tests such as tensile test, hardness test, three-point bending test and Charpy impact test were all carried out on the ECAPed CP-Ti through 3 passes. The microstructural evolution reveals that by applying the ECAP process, coarse grain (CG) structure develops to UFG/NC structure. Moreover, the results of the mechanical tests show that the process significantly increases the yield and ultimate tensile strengths, bending strength, hardness and fracture toughness of the commercially pure titanium so that it can be used as a replacement for metallic alloys used as biomaterials.     

Effect of cold rolling on the structure and mechanical properties of sheets from commercial titanium

Changes in the microstructure and texture due to cold rolling of sheets from commercial titanium with initial coarse-grained and submicrocrystalline structures are studied. The submicrocrystalline structure is obtained in titanium by uniform severe plastic deformation. The permissible degrees of deformation for rolling of titanium with different grain sizes are determined. The microstructure and mechanical properties of sheets fabricated by rolling at room temperature are studied. Comparative analysis of properties of titanium specimens with submicrocrystalline structure obtained by different methods is performed.     

工业纯钛焊接接头的表面纳米化及其性能

利用表面机械研磨法对工业纯钛焊接接头的表面进行处理，通过X射线衍射及透射电镜分析，表明经处理后的工业纯钛焊接接头表面晶粒尺寸达到了50nm左右，纳米化深度约30～40μm。显微硬度试验结果表明，经处理后样品表面的硬度有很大提高，焊缝和热影响区的硬度趋于一致。腐蚀试验证明工业纯钛焊接接头经表面纳米化处理，其耐盐酸腐蚀性能有所提高。     

工业纯钛激光焊性能及组织分析

探讨了激光对焊方法对工业纯钛板材热处理前后力学性能度组织的影响，通过对板材激光对焊后母材、热影响区、焊缝消应力退火前后组织性能的分析对比，表明：纯钛激光焊方法用于钛带生产，可获得较为理想的组织。