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选区激光熔化(SLM)成形的TC4样件强度高、塑性差、各向异性明显。对SLM TC4成形件进行固溶时效、循环退火、循环球化退火+固溶时效三种热处理,采用光学显微镜、扫描电子显微镜、拉伸试验机对热处理所得成形件进行组织观察和性能测试。研究表明SLM TC4成形件微观组织由马氏体α′和马氏体α″组成,强度为1220 MPa左右,延伸率最高达13%;TC4成形件经热处理后板条α相粗化,有等轴α相产生,板条状α相长宽比降为5左右,固溶时效处理和循环球化退火+固溶时效处理的TC4成形件组织中产生二次α相;先950℃固溶1 h,之后550℃保温4 h,此条件下所得成形件的综合力学性能最好,其抗拉强度达到957.9 MPa,延伸率为17.6%,且所有拉伸性能指标的各向异性小于1.2%;循环球化退火+固溶时效处理的样件塑性很高,延伸率达18.3%,同时强度的各向异性不超过2%,固溶时效与循环球化退火+固溶时效处理后力学性能超过国家锻件标准。经过循环退火处理的TC4成形件强度损失较大,但塑性与另外两种热处理工艺相差不大。 相似文献
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《中国激光》2017,(9)
研究了退火、两相区固溶、固溶时效三种热处理方法对激光选区熔化(SLM)技术成形TC4钛合金微观组织和力学性能的影响。结果表明,在SLM成形TC4钛合金中形成了细针状马氏体组织,几乎不存在β相,强度较高,塑性较差;经过840℃/2h/空冷(AC)退火处理后,TC4钛合金的显微组织由(α+β)相构成,具有较高的强度和塑性;经过940℃/1h/水淬(WQ)固溶处理后,β相的含量增加,晶粒长大,形成交错的(α+β)网篮组织,强度明显下降,塑性提高;经过940℃/1h/WQ+540℃/4h/AC固溶时效处理后,形成了均匀弥散的(α+β)相,α相粗化,强度降低,塑性小幅提高。TC4钛合金经过热处理后,内部残余应力减小,变形开裂倾向降低。采用840℃/2h/AC退火处理工艺,可使SLM成形TC4钛合金获得较佳的强度/塑性匹配。 相似文献
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采用激光直接沉积的方式成功制备无冶金缺陷的高质量沉积态样件,研究固溶温度(910~970℃)和时效温度(500~600℃)对沉积态样件的相组成、显微组织和拉伸性能的影响。研究结果表明,沉积态和固溶时效态合金的显微组织均由大量的α-Ti(α)相和少量的β-Ti(β)相构成;另外,随着固溶温度和时效温度的升高,显微组织内的α相由细长的针状转变为短棒状。拉伸性能方面,确定了固溶时效态试样(940℃/1 h/WQ+550℃/4 h/AC、970℃/1 h/WQ+550℃/4 h/AC和940℃/1 h/WQ+600℃/4 h/AC)的拉伸强度指标高于锻件国家标准要求(σb≥895 MPa,σ0.2≥828 MPa,δ≥10%);断口形貌均属于塑性断裂。 相似文献
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《中国激光》2018,(11)
研究了热处理对激光立体成形DZ125高温合金凝固微观组织的影响。结果表明,随着固溶处理温度的升高,初生γ′相的溶解增多,在1240℃固溶2 h后初生γ′相全部固溶;Ni_5Hf相和MC_((1))碳化物在高温保温时发生固态相变,经1180℃/2 h/空冷(AC)热处理后Ni_5Hf相全部分解,释放的Hf元素与基体固溶的C原子结合形成MC_((2))碳化物,部分MC_((1))碳化物在1000℃保温12 h后转变为M_(23)C_6或M_6C型碳化物;完全固溶处理后在1100℃和870℃时效时,γ′颗粒尺寸的变化规律及经验分布函数与Lifshitz-Slyozov-Wagner(LSW)理论预测的较为一致。拟合得到γ′相的粗化激活能为231.43 kJ/mol,γ′颗粒的粗化受Ti、Al原子在Ni中的扩散控制。 相似文献
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BT25y高温钛合金固溶处理及热暴露过程中硅化物的析出机制 总被引:4,自引:0,他引:4
TEM观察了BT25y高温钛合金硅化物在固溶处理以及热暴露过程中的析出行为,结合Calphad相图计算技术研究了该合金硅化物的析出机制。在经单相区990℃固溶处理后的个别样品和两相区940℃固溶处理后的部分样品中,观察到(Ti,Zr)5 Si3,硅化物颗粒,依据计算,分析这些硅化物可能是由于Si分布不均匀,局部浓度超过0.3%而析出的;在两相区940℃固溶处理后的样品中还观察到平衡析出的(Ti,Zr)6 Si3硅化物颗粒。两种固溶处理后的样品,在700℃热暴露过程中都有大量细颗粒(Ti,Zr)6 Si3硅化物弥散析出。 相似文献
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本文通过对HPb59—1镀金件表面腐蚀凹坑点产生的原因分析,发现由于电镀前处理工艺不当是产生缺陷的原因,经过选用碱性较低的除油剂使这一问题得到解决。 相似文献
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This study focused on the use of accelerated testing to find out why tantalum capacitors fail. Stress effects of humidity, temperature, and ripple voltage were examined in different combinations. Results show that a standard 85/85 test with combined enhanced moisture and temperature does not result in failure of tantalum capacitors in 2500 h. However, with added ripple voltage, failures may occur in a relatively short time. High relative humidity and high temperature both affect water diffusion, but apparently increased ripple voltage in 85/85 testing causes tantalum capacitor characteristics to weaken and capacitors to fail. The paper elaborates on the possible reasons. 相似文献
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《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2008,16(6):611-619
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基于峰值电流检测脉宽调制技术原理,设计了一种新颖的应用于单片降压型DC-DC转换器的控制电路。针对峰值电流采样和PWM比较器电路技术,提出了一种新颖的电路结构。其中,PWM比较器和逻辑及驱动电路由升压电路驱动,节省了一个电平转换电路,降低了电路功耗;PWM比较器直接对功率管和镜像管电流采样,无需使用运算放大器,简化了电路结构。采用华虹宏力BCD350GE工艺进行设计,流片测试表明,电路可实现3V到36 V宽幅输入,500 mA满载输出。在输入24 V电压,输出3.3 V电压时,纹波为2.3 mV。 相似文献
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Petrovic V. Ortega R. Stankovic A.M. Tadmor G. 《Power Electronics, IEEE Transactions on》2000,15(5):871-880
This paper addresses the problem of torque ripple minimization in permanent magnet synchronous motors (PMSMs) and proposes an adaptive feedback structure as a solution. A model of PMSM that includes a torque ripple phenomenon is first developed and tested. While slightly different from the conventional one, our model is still compact and suitable for control. All parameters of the model have physical interpretation, and can either be measured directly or estimated in a numerically reliable procedure. An adaptive control algorithm is then described, enabling speed tracking while minimizing the torque ripple. Finally, the proposed algorithm is verified in simulations and implemented in a hardware setup. Experimental results show significant reduction of torque ripple (by 27 dB). Extensive analysis and simulations of hardware imposed limitations were performed as well, revealing and quantifying the issues that might affect practical ripple minimization performance 相似文献
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塑封器件中高聚物的失效分析 总被引:1,自引:1,他引:0
文章分析了塑封器件中高聚物在封装固化过程中和使用过程中常见的损伤或失效,结果表明:封装固化过程中,当高聚物材料收缩受到周围材料的约束时,由于残余应力的存在,可引起气孔、孔隙、微裂纹,即形成了一系列微小缺陷;在后续的生产工艺以及产品使用过程中的热-机械载荷作用下,固化中产生的微小缺陷或损伤会扩展、汇合而形成宏观裂纹,导致... 相似文献
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Mingjuan Zhu Perreault D.J. Caliskan V. Neugebauer T.C. Guttowski S. Kassakian J.G. 《Power Electronics, IEEE Transactions on》2005,20(2):276-285
An active ripple filter is an electronic circuit that cancels or suppresses the ripple current and electromagnetic interference generated by the power stage of a power converter, thus reducing the passive filtration requirements. This paper explores the design of feedforward active ripple filters for current ripple cancellation, including the design tradeoffs, advantages, and limitations of different implementation methods. The design and performance of an active filter using a novel Rogowski-coil current sensor is discussed in detail. Experimental results from a prototype converter system using this approach are presented, and quantitative comparisons are made between a hybrid passive/active filter and a purely passive filter. It is demonstrated that substantial improvements in filter mass and converter transient performance are achievable using this active ripple filtering method. 相似文献
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一种新型的低纹波开关电源 总被引:5,自引:0,他引:5
传统开关电源具有输出纹波大、辐射干扰大等缺点,应用场合受到限制.文中分析了传统开关电源输出纹波的产生机理,介绍了斜波驱动方式的优点和新型电源专用集成电路LT1533的工作原理,给出了非隔离式24 V输入,5V、1A输出的推挽变换器设计实例.试验结果表明输出纹波降低到小于2 mV(峰-峰值). 相似文献