工业纯钛表面高能喷丸对仿生矿化合成羟基磷灰石涂层的影响

将表面抛光和高能喷丸处理的工业纯钛在5mol/L NaOH溶液中处理后,在模拟体液(SBF)中矿化生成羟基磷灰石(HAP)涂层.用扫描电镜(SEM)、X射线衍射仪(XRD)、电子探针(EPMA)和红外光谱仪(FT-IR)分析了涂层表面形貌和成分,探讨了表面高能喷丸工艺对钛基体及涂层的影响.结果表明,通过仿生矿化法,生成了钙磷比为1.30的碳酸化的HAP涂层;与抛光钛相比,高能喷丸工艺增加了钛基体的表面化学反应活性,从而加快了钛基体上HAP沉积速度;增加了表面粗糙度,提高了涂层与基体的结合力.     

工业纯钛表面高能喷丸对溶胶-凝胶法制备羟基磷灰石涂层的影响

将表面抛光和高能喷丸处理的工业纯钛在8mol/L NaOH溶液中处理后,采用溶胶-凝胶(sol-gel)法在其表面制备羟基磷灰石(HAP)涂层.用扫描电镜(SEM)、X射线衍射仪(XRD)对涂层的表面、截面形貌及成份进行了分析;用拉伸试验机测试了涂层与基体之间的结合强度;动态凝血实验测试了涂层的血液相溶性;探讨了高能喷丸工艺对钛基体及涂层的影响.结果表明,通过sol-gel法,在两种基体表面制备了HAP涂层;高能喷丸工艺增加了基体的表面粗糙度和表面积,利于HAP的涂覆.提高了涂层与基体间的结合力,由抛光处理的10MPa提高到喷丸处理的30MPa;喷丸基体表面的涂层具有更好的抗凝血性.     

高能喷丸预处理对钛表面组织及生物活性微弧氧化层的影响

为了提高钛表面的生物活性,利用微弧氧化工艺分别在普通粗晶钛和表面高能喷丸细晶钛上制备了多孔TiO2氧化层。经光镜和透射电镜观察,喷丸钛表面形成厚度40μm,直径100～200nm的等轴晶结构层。利用扫描电镜(带能谱分析)和X射线衍射仪对氧化层表面形貌、成分和相组成进行分析。结果表明,高能喷丸钛的表面生成的氧化层中含有α-Ca3(PO4)2相且钙磷百分含量提高。在粗糙的高能喷丸钛表面,微弧氧化速度在不同位置有所不同,氧化层与基体形成微机械咬合,基层结合力提高。     

喷丸处理对6151-T6铝合金旋转弯曲疲劳性能的影响

对经过电解抛光、喷丸处理和喷丸处理再抛光的三种6151-T6铝合金试样的表面粗糙度及喷丸处理后试样表面硬化层的硬度进行测试。对三种表面状态不同的铝合金材料进行旋转弯曲疲劳实验。研究喷丸处理试样表面残余应力随疲劳实验的变化情况,以及喷丸处理对该铝合金疲劳性能的影响。结果表明:喷丸处理对材料疲劳性能的影响与加载的压应力水平有关。当加载的压应力与表面残余压应力之和不超过材料表面硬化层的循环屈服强度时,硬化层中的残余压应力在疲劳过程中不发生应力松弛,疲劳寿命得到大幅度提高;反之,将发生应力松弛现象,疲劳寿命的提高程度受残余压应力松弛程度的影响。此外,喷丸处理造成的材料表面粗糙度的增加,在全应力幅范围,使材料的疲劳寿命略有降低。     

工业纯钛低周疲劳应力—应变响应

测量了工业纯钛低周疲劳的应力－应力响应,选择动态模量ＤＭ与弹性模量ＥＭ之比值ＤＭ．ＥＭ衡量材料的相对“软”“硬”程度,发现在各个应变幅下ＤＭ．ＥＭ有向０．３５－０．４０靠近的趋势。讨论了新的参量ＤＭ．ＥＭ与循环硬化循环软件之间的关系。     

超声冲击对纯钛材焊接接头疲劳性能的影响

目前,有关超声冲击法对工业纯钛焊接接头疲劳性能改善效果的影响研究报道不多。采用超声冲击处理方法对工业纯钛TA2焊接接头进行全覆盖强化处理,通过疲劳对比试验分析了不同超声冲击处理时间对TA2焊接接头疲劳性能的影响;通过接头微观组织、断口形貌观察分析了超声冲击处理提高TA2焊接接头抗疲劳断裂性能的微观机理。结果表明,在200 MPa应力条件下,原始焊态试样平均历经11 645次循环就已断裂,经超声冲击处理3 min的焊接试样平均历经23 424次循环后才断裂,疲劳寿命提高约1倍;在超声冲击过程中,试样表层受到大的应变量、高应变速率和重复载荷的作用,使得形变孪晶不断增加;重复载荷的作用,可以再次在内部产生更加细小的孪晶,孪晶与孪晶间重复交割导致晶粒进一步细化。     

高能喷丸对AZ31镁合金耐腐蚀性及硬度的影响

采用高能喷丸对AZ31镁合金棒材端面进行表面自纳米化处理,利用失重法研究了AZ31镁合金喷丸试样和未喷丸试样在中性5%NaCl溶液中的腐蚀行为。利用扫描电子显微镜(SEM)、能量色谱仪(EDS)对塑性变形层腐蚀后的表面形貌、元素分布进行了表征,利用微观硬度计测试了由喷丸表面到基体的硬度变化。结果表明,喷完后AZ31镁合金试样的腐蚀速率明显大于未喷丸的试样,随着腐蚀时间的延长,喷丸试样的腐蚀率急剧减小,然后缓慢降低,在喷丸表面形成了1层厚度约150μm的塑性变形区,在喷丸表面有裂纹存在。晶粒细化显著提高了母材表面的微观硬度,喷丸表面的微观硬度最高达到135HV,是母材的2倍多。     

喷丸对扭转疲劳性能的影响EI

对扭转试样进行喷丸和预应变,经强化后试样的对称扭转疲劳极限比磨削态提高20～30％。 断口分析表明,在疲劳极限水平附近运转的扭转疲劳断裂是由正应力引起的,断口与轴线成45°。喷丸试样的硬度分布曲线表明,在表下一定深度存在软化区,而裂纹萌生的位置比软化区更深。 喷丸后扭转疲劳极限提高的主要原因是残余压应力的作用。在喷丸前或后进行预应变均使疲劳极限下降。这和预应变时造成的损伤或在夹杂周围造成裂纹有关,它使疲劳寿命降低。     

复合喷丸提高等轴状TC4钛合金的疲劳性能

首先对等轴状TC4钛合金疲劳试样表面进行了不同时间的高能喷丸,制备出一定深度的纳米表层,然后采用小尺寸弹丸进行表面损伤修复喷丸,提高纳米表层质量,最后对不同喷丸状态的试样进行了疲劳试验。结果表明:复合喷丸使等轴状TC4钛合金的疲劳强度相比未喷丸状态提高了34%,在单纯高能喷丸纳米化方法的基础上进一步提高了12%;高能喷丸在试样表面形成的损伤阻碍了表层纳米化提高疲劳强度的效果,通过修复喷丸可以修复部分高能喷丸损伤。     

超声冲击处理钛合金焊接接头的性能研究

采用超声冲击工艺,处理了钛合金两种型式的焊接接头。试验结果表明:超声冲击处理可显著降低接头焊接残余应力,并可提高接头的疲劳强度和疲劳寿命。其中对于Ti80合金的对接接头和十字接头,疲劳极限分别提高22.7%和64.5%,疲劳寿命分别提高5.4倍和13.5倍;对于TA2和Ti75合金的对接接头,焊接残余应力分别降低68%和65%。     

喷丸强化对2XXX铝合金疲劳寿命的影响

研究喷丸对2XXX铝合金拉-拉疲劳性能的影响。对未喷丸试样和喷丸强化试样的微观组织、显微硬度、残余应力和拉-拉疲劳性能进行对比分析。结果表明:喷丸处理后,试样的组织和微结构未发现明显变化,但其粗糙度、残余压应力和显微硬度有所提高,分别是未喷丸试样的6.25倍,3.85倍和1.12倍;拉-拉疲劳性能显著提高,其中值疲劳寿命是未喷丸的1.67倍。在99.9%存活率下,喷丸试样的安全寿命是未喷丸试样的1.45倍。且表面喷丸强化后疲劳裂纹源由多个变为一个。     

Effect of Varying Carbon Content and Shot Peening upon Fatigue Performance of Prealloyed Sintered Steels

The aim of the work was to find out how the modification of surface treatment and microstructures affect the fatigue characteristics of the considered sintered materials.Two different systems were prepared:as-sintered and shot peened prealloyed sintered(Astaloy CrL based)steels with addition of 0.5%and 0.7%C.Sintering was carried out in laboratory tube furnace in an atmosphere of pure gases 75%N2+25%H2.The sintering temperature was 1180-C and sintering time was 60 min.Heating and cooling rates were 10-C/min...     

Enhancement on Fatigue Property of Aluminum Alloy Welded Joint by Utilizing Trailing Peening

The fatigue properties of 2024T3 aluminum alloy welded joint treated by different peening methods were examined. The different effects on fatigue performance of high strength aluminum welded joints were compared with each other by carry out a series tests     

Internal Friction and Elastic Study on Surface Nanocrystallized 304 Stainless Steel Induced by High—energy Shot Peening

The 304 stainless steel with nanostructured surface layer was successfully obtained by using the high-energy shot peening(HESP) method.The internal friction and Young‘s modulus of this kind of surface nanocrystallized material were dynamically measured by means of the vibrating reed apparatus.The results implied that different treatment time could induce different microstructure and distribution characteristic of defects in this kind of materials.It is also demonstrated that there is a transition layer between the nano-layern on surface and the coarse grain region inside.The transition layer obviously has certain influence on the overall mechanical properties.     

抗疲劳的表面强化技术

飞行器零部件多在交变载荷下服役,易发生疲劳失效。介绍了目前主要应用和在研的三种抗疲劳表面强化技术：喷丸强化、孔挤压强化和激光冲击强化,以及三种技术的工艺特点,设备,研究情况和应用情况。     

Thermal Stability of Surface Layer Microstructures of Commercially Pure Titanium Treated by High Energy Shot Peening

Commercially pure titanium was treated by high energy shot peening, and annealed at a series of temperatures. The surface layers are characterized by means of scan electronic microscope, X-Ray diffraction, transmission electronic microscope and micro-hardness testing machine. The results showed that microhardness of surface layers decreases with anneal temperature, the tendency of microhardness is similar to unannealed one, in other words, the more close to the surface, the more rapidly the hardness decreases, after reaches the depth of 50 μm, the decrease becomes steadily. But the sub-surface microhardness decreased suddenly over 500 ℃, From 550 ℃ to 650 ℃, the microhardness of surface layers almost unchanged.Observing by TEM and SEM, the grain sizes of pure titanium surface layers have increased below 500 ℃; Deformation twins begin disappearing obviously at 550 ℃; The nano-scaled grains within about 10 micrometers from surface existed even at 550℃.Surface nanocrystallization is well known as one of important methods to improve surface properties. The thermal stability of nanocrystalline microstructures was related to their preparation and application. The commercial pure Ti thermal stability of nanocrystalline and deformed microstructures induced by high-energy-shot-peening (HESP) technique was investigated. The nanostructured surface and deformed sub-surface layers of specimens were prepared through HESP treatment. The thermal stability was characterized through XRD analyses of surface layers, SEM and TEM microstructure observation and microhardness measurement of specimens annealed in different temperature in the air after HESP treatments. The results showed that after HESP treatment, the microhardness of surface layers increased with treatment time, especially in the rang of about 40 micrometers from the surface, the microhardness increase was obvious. The surface microhardness decreased gradually with annealing temperature, but the sub-surface microhardness decreased suddenly over 500℃. From 550 to 650 ℃, the microhardness of surface layers almost unchanged, and is still higher than that of the undeformed microstructure. SEM observation showed that at and below 500 ℃, the microstructure changes were not obvious. At 550 ℃, the grains in surface layers grew remarkably both in SEM and TEM images at 20 micrometers deep, and the deformed twins formed in HESP treatment could be seen in the subsurface. In addition, the TEM images showed that even at 550 ℃, the nanosized grains existed within 10 micrometers from surface.     

喷丸强化对0Cr13Ni8Mo2Al钢疲劳性能的影响

研究了表面喷丸强化后表面残余应力,表面粗糙度和表面层残余应力场对0Cr13Ni8Mo2Al钢疲劳性能的影响,结果表明：0Cr13Ni8Mo2Al钢经喷丸强化后,在表面层残余应力场的作用下疲劳裂纹源由表面被“驱赶”到表面强化层下,疲劳寿命得到显著提高。     

喷丸强化对OCr13Ni8Mo2Al钢疲劳性能的影响

研究了表面喷丸强化后表面残余应力、表面粗糙度和表面层残余压应力场对0Cr13Ni8Mo2Al钢疲劳性能的影响.结果表明:0Cr13Ni8Mo2Al钢经喷丸强化后,在表面层残余压应力场的作用下疲劳裂纹源由表面被"驱赶"到表面强化层下,疲劳寿命得到显著提高.