激光相变硬化及感应表面淬火技术对结构钢组织和耐蚀性能的影响

通过激光相变硬化和超音频感应表面淬火两种表面淬火方法,对45钢进行表面淬火,并进行表面硬度测试、拉伸试验、组织观察,探究在该两种表面淬火方法下的45钢最优工艺参数,比较相同移动速度下两种淬火方法的力学性能;利用Autolab PGSTAT 302N电化学工作站对经过两种表面淬火及原始试样进行经典三电极测试,分析其极化曲线变化趋势,比较其耐蚀性的优劣;同时,对比了同条件下腐蚀前后试样力学性能及表面的腐蚀行为。     

大型双曲率蒙皮拉伸模高效数控加工技术

为了提高大型双曲率蒙皮拉伸模的加工效率,设计了一种优质高效的数控加工工艺。借助三维CAM软件,编制数控加工程序,合理排布粗加工、半精加工、精加工的刀具轨迹,生成数控机床专用NC代码。利用几何仿真软件,对NC代码进行仿真检查,避免撞刀、过切等意外情况的发生。最后,对拉伸模进行实际的切削加工,模具工作型面质量良好,加工精度符合设计图样要求,表明了此加工工艺的可行性,为大型双曲率蒙皮拉伸模的高效数控加工提供了一种工艺方案。     

钛合金材料室温拉伸试验影响因素的研究

通过试验分析,研究对比同种材料不同设备、取样位置和方向、拉伸速率、控制方式、试样平行长度段、加工方式等对性能数据的影响。研究结果表明,取样位置和方向、加工方式是影响钛合金力学性能的主要因素,其他因素的影响可以忽略。分析认为,取样位置的选取和加工工艺的优化,同时保证试样加工的质量,是确保拉伸数据准确必不可少的重要控制环节。     

局部激光热处理对DP1180双相钢成形性能的影响

采用不同激光加工参数对DP1180双相钢试样进行局部激光热处理,研究该加工工艺对双相钢成形性能的改善影响。结果表明,当激光加工温度为650~700℃时,试样塑性得到明显改善,伸长率从5%提高至17.4%左右,最大软化程度可达30%以上。通过对比分析模拟及由试验测得的双相钢中心位置的温度变化曲线,验证了激光热处理数值计算模型的合理性以及积分球测激光吸收率的准确性。     

新型低碳Mn-Mo-Nb-Cu-V型机械结构用高强钢的热处理工艺优化

采用不同工艺对新型低碳Mn-Mo-Nb-Cu-V型机械结构用高强钢试样进行了热处理,并进行了试样冲击性能和拉伸性能的测试与分析。结果表明,在试验条件下,随淬火温度或回火温度不断上升,试样的冲击吸收功、抗拉强度、屈服强度和断后伸长率先增大后减小,试样冲击性能和拉伸性能先提高后下降。新型低碳Mn-Mo-Nb-Cu-V型高强机械结构用钢的最佳热处理工艺参数为:920℃×15 min淬火和710℃×6 h回火。     

深微孔电火花加工非电参数工艺规律研究

在深微孔电火花加工中,工作液及电极材料等非电参数的选择对加工效率及加工质量有极大的影响,揭示这些非电参数的工艺规律对提高深微孔电火花加工性能有重要的研究意义.利用煤油和去离子水两种工作液,以加工效率为目标,在不同条件下开展工艺试验,得出最适宜的工作液在加工45钢和紫铜材料工件时为去离子水,加工铝合金材料工件时为煤油;利用黄铜丝、钨丝及钼丝3种电极材料,同样以加工效率为目标开展工艺试验,得出最佳电极材料在加工45钢工件时为钨,加工紫铜材料工件时为钨和钼,加工铝合金材料工件时为黄铜.上述研究在深微孔电火花加工中合理选择工作液及电极材料方面做出了有益的探索,其研究成果为深微孔电火花加工高效率、高质量的开展提供了重要的借鉴.     

试验温度对不同工艺下的TRIP钢拉伸性能的影响

研究拉伸试验温度对TRIP钢力学性能的影响规律,对于板带温加工成型的工艺参数探索有重要的参考价值。将A、B两种TRIP钢经过热轧后在盐浴炉中分别保温3 min和5 min,然后在50～350℃进行拉伸试验研究,对比其力学性能变化。结果表明,A、B试样在200℃和250℃拉伸时,抗拉强度因TRIP效应而达峰值,分别达到895 MPa和881 MPa;而伸长率降低不明显,在100℃时,伸长率达到36%和38%。300℃和350℃时,不再发生应变诱导马氏体相变,故抗拉强度、伸长率均降低。B试样因其残余奥氏体更加稳定而具有更显著的TRIP效应,其力学性能优于A试样。     

高强钢点焊接头动态失效载荷探讨

以1.2 mm厚的两种典型高强钢材料HC340LAD+Z和HC340/590DP为研究对象,采用剪切拉伸和T型撕裂拉伸两种点焊结构试样,测试了0.001~16.7 m/s不同拉伸速度下的动态失效载荷,分析了不同材料、加载方式及拉伸速度等因素对失效载荷的影响。从试验结果得出了失效载荷与拉伸速度的拟合关系,对汽车生产点焊工艺有一定的参考价值。     

H13钢表面镀铬和气体渗氮复合处理的组织及性能

对调质后的H13钢进行镀铬+540 ℃气体渗氮处理,获得氮化铬表层,然后将其进行耐磨试验,并与同温度经常规气体渗氮及离子渗氮后的H13钢试样进行组织及耐磨性对比。结果表明:3种工艺处理后试样的主要磨损机制为粘着磨损和磨粒磨损,镀铬/渗氮试样表面摩擦因数最低,为0.44,耐磨性最好,但镀铬+渗氮层与基体的结合力最差。     

不同形状试样对12MnNiVR拉伸性能的影响

对不同厚度12MnNiVR钢板的两种不同形状拉伸试样进行对比试验,分析了试样形状对强度、断后伸长率的影响。结果表明:12MnNiVR钢种圆形试样拉伸性能优于板状试样,合格率较高。     

亚共析钢搅拌摩擦加工组织与力学性能

采用K40钨钴硬质合金搅拌头对3 mm厚热轧退火态亚共析钢板进行了搅拌摩擦加工,对加工区域的宏观形貌、微观组织及力学性能进行了分析．结果表明,搅拌区和热力影响区为先共析块状铁素体、“针状”铁素体及珠光体,组织转变受动态再结晶和相变共同作用,热影响区组织为等轴状铁素体和片层状珠光体．搅拌摩擦加工对各区域中珠光体及析出渗碳体的分布形态影响显著．搅拌摩擦加工后试样显微硬度明显增加,抗拉强度相比母材提高8.2%,断裂位置位于母材处,加工前后试样断裂形式均为微孔聚合韧性断裂．固溶强化与相变强化对硬度和抗拉强度的提高起主要作用．     

Ultrasonic non-destructive evaluation with spatial combination of Wigner–Ville Transforms

This paper introduces a novel ultrasonic signal combination technique to be applied in detection systems based on multiple transducers. The technique uses a spatial combination approach that considers the specimen inspection from several apertures located in different planes. Information received from transducers is fused in a common integrated pattern with a signal to noise ratio (SNR) improvement. The result of the combination is a high quality image of the inspected material obtained from simple A-scans.The method is based on digital signal processing techniques, more concretely time–frequency analysis. Combination is performed by means of the Wigner–Ville Transform preserving temporal and frequencial information. Temporal techniques for combination are presented and the results obtained from both techniques are compared using the SNR.     

扩散连接接头质量评价现状

回顾扩散连接接头质量无损检测与评价的现状，介绍目前研究较多的超声反射法、超声信号处理、超声成像及实时监控等方法。由于扩散连接接头无损检测的复杂性，大多数检测技术还处于实验室研究阶段，因此，深入研究超声波与扩散连接界面的相互作用和先进的信号分析处理方法，对扩散连接接头质量的评价具有重要意义。     

Large-scale manufacturing of aluminum alloy plate extruded from subsize billet by new porthole-equal channel angular processing technique

To manufacture plate by the combination of equal channel angular processing (ECAP) and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing (P-ECAP), was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3–5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 °C. The effective strain exhibited ascending trend in the corner of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress.     

Microstructure and mechanical properties of Al-6061-T6 alloy welded by a new hybrid FSW/SSW joining process

In this study for the first time, the effects of decrease in heat inflow to the weld metal in friction stir process by utilising semisolid processing and decreasing the pin rotational speed as well as increasing the pin transverse speed were examined. As a result, the characteristic loss of hardness and strength in the weld zone were eliminated. The results showed that by approaching the ultrafine microstructure in the weld zone through the hybrid FSW/SSW process, the hardness and elongation values reached to 90?Hv and 8.88%, respectively. These are only slightly different from those of the base metal of the welded samples. Furthermore, the ultimate tensile strength of the samples welded by the hybrid technique was found to be about 167?MPa that was higher than those of the samples welded by friction stir welding (151?MPa) and semisolid welding (114?MPa) techniques.     

基于BP神经网络的TC11钛合金工艺-性能模型预测

材料工艺与性能的关系具有复杂、非线性交互等特点。本文根据TC11钛合金力学性能与其影响因素之间的映射关系,以大量的试验数据为基础,建立了BP神经网络模型。模型的输入包括锻造温度、锻后冷却方式等热加工工艺参数;输出为常用的力学性能指标,即抗拉强度、屈服强度、延伸率和断面收缩率。运用该模型对TC11钛合金力学性能进行了预测,并通过试验数据对模型的预测精度进行了可靠性验证。同时,运用已建立的神经网络模型对TC11钛合金工艺参数与力学性能的关系进行了分析。结果表明,所建立的力学性能预测模型具有良好的外推能力,并且可以很好地反映出该合金的工艺-性能之间的复杂关系。     

数控铣削加工刀具运动轨迹的实验研究

在加工复杂曲面时,利用数控铣削能获得比较高的表面质量,因此其应用非常广泛。不同的刀具运动轨迹与加工工件的表面质量和加工效率密切相关。通过实验比较不同的刀具运动轨迹和运动轨迹相同但步长和深度不同时对加工质量、加工效率等的影响。通过实验所得结论可为现场加工提供数据参考。     

NiCrSiBC alloy: microstructure and hardness of coatings processed by arc and laser

The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6^® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides.     

Influence of roll and solution treatment processing on shape memory effect of Fe-14Mn-5Si-9Cr-5Ni alloy

The shape memory effect was studied in an Fe-14Mn-5Si-9Cr-5Ni alloy rerolled at 1123 K after hot rolling at 1423 K, followed by solution treatment at different temperatures. It was found that the alloy exhibits a maximum degree of shape recovery in a bending test and a complete recovery tensile strain of 2.2% in samples that were solution heated at 973 K for 600 s and then quenched in water. The rerolled processing at 1123 K after hot rolling at 1423 K and the microstructure under solution treatment state are important for obtaining a good shape memory effect in the alloy.     

多通管接头磨粒流光整均匀性研究

目的 提升航空油路中多通管接头内壁磨粒流光整加工效果.方法 以三通、四通金属管接头为研究对象,针对零件的材料特性、结构特性设计相关实验,研究多通管接头管道内表面磨粒流光整工艺中加工时间及加工流道对管道内壁粗糙度、材料去除量、表面质量一致性的影响.结果 加工开始时管道表面糙度Ra下降缓慢,在60 s后粗糙度开始加速下降,...