共查询到20条相似文献,搜索用时 109 毫秒
1.
燃气轮机涡轮叶片工作高达800℃,转速每分钟高达万转以上,由于某型燃气轮机曾出现过涡轮叶片叶身排气边裂纹,其出现大裂纹曾有30台机组,故障叶片裂纹主要发生在离叶尖1/3~2/3处,裂纹有的长达31毫米,裂纹断口经金相检查,属于振动疲劳性的穿晶脆断和沿晶界 相似文献
2.
GH4169合金在电子束焊后,多次发现在热影响区腐蚀检查时,有沿基体晶界类似裂纹的"黑线",对其进行金相分析、扫描电镜观察和能谱分析结果表明,GH4169合金在电子束焊后腐蚀检查沿晶界的黑线不是裂纹,而是由铌、锆等元素形成的合金相. 相似文献
3.
在备有拉伸装置的扫描电镜下,观察了 Al—2.56 Li—1.29Cu 合金拉伸变形及断裂过程。观察结果表明,在固溶淬火及190℃时效状态下,主要析出相为δ’相。随着时效时间的延长,拉伸断口逐渐由韧窝穿晶型向沿晶突脊型及沿晶韧窝型过渡。在固溶状态下,当拉伸应力超过届服强度以后,出现平直滑移带及交叉滑移带;拉伸裂纹在晶内滑移带及晶界处萌生,并主要沿滑移带扩展。欠时效状态下,δ’相的析出量增多,使共面滑移加剧,交叉滑移带难于形成;裂纹除沿晶界扩展外,也有少部分沿滑移带扩展。在达到峰时效以后,交叉滑移带消失;裂纹在三角晶界处萌生并沿晶界扩展。 相似文献
4.
该文采用工程实践中常用的平均应力法、局部塑性应变法,参照国家军用标准GJB 241A—2010,确定应用FGH96合金的高压涡轮转子超转/破裂试验参数,对FGH96合金涡轮盘和封严盘进行强度分析,在旋转试验器上完成超转和破裂试验考核。试验后对故障件后挡块进行了失效分析,结论为冶金缺陷造成1件后挡块失效,不影响试验验证结论。 相似文献
5.
《理化检验(物理分册)》2021,57(4)
某发动机涡轮叶片在试车过程中缘板处出现掉块和裂纹。采用宏观分析、低倍腐蚀、断口分析等方法对涡轮叶片缘板处的掉块原因进行了分析。结果表明:涡轮叶片缘板出现掉块和裂纹性质为持久断裂失效,涡轮叶片缘板裂纹产生原因与缘板位置小角度晶界角度过大有关。建议将此型涡轮叶片的小角度晶界技术条件要求由不大于8°提高到不大于6°。 相似文献
6.
7.
曲轴主轴颈表面裂纹原因分析 总被引:2,自引:0,他引:2
通过对45钢曲轴主轴颈表面裂纹的综合分析,揭示了裂纹产生原因系在调质处理的淬火过程中,网状铁素体沿晶界析出,使晶界严重弱化,最终导致在中频淬火过程中形成以沿晶为主的淬火裂纹。 相似文献
8.
《理化检验(物理分册)》2001,(9)
二 问答题2 4 .沿晶断裂是裂纹沿晶界扩展而造成金属材料的脆断。在失效分析中常见的有以下几种类型的沿晶断裂形式 :(1)晶界沉淀相造成的沿晶断裂。晶界上不连续的沉淀相在外力作用下 ,在其周围首先形成微孔 ,后经长大连接成为晶界裂纹 ,最后造成沿晶断裂 ,此时为沿晶韧窝断裂。若晶界上沉淀相粒子形成脆性网状薄膜 ,此时断裂为脆性薄膜分裂型。(2 )杂质元素偏聚造成的沿晶脆断。杂质元素P ,S ,Sb ,As和Sn等在晶界上存在并达到一定浓度时 ,它们将降低晶界内聚能 ,从而引起脆断。如高强度低合金钢的回火脆性就是典型例子。(3)由环… 相似文献
9.
用扫描电镜对18Cr-18Mn-0.7N高氮奥氏体钢低温脆断中裂纹的形成、扩展及断面进行了分析.结果表明,低温脆断中,首先沿退火孪晶界及晶界形成微裂纹,微裂纹穿晶连接使裂纹扩展,其结果导致断口上形成三种断裂刻面,即光滑平面状退火孪晶界断裂刻面、光滑曲面状沿晶断裂刻面及粗糙不平的穿晶断裂刻面. 相似文献
10.
前言 航空喷气发动机上大量采用高温合金制造各种零部件,焊接是制造中的主要工艺。合金零件进行钨极氩弧焊时,焊缝金属中常出现结晶裂纹,热影响区则出现液化裂纹,如图1所示。金相分析表明,这些是沿晶界和核晶间形成的热裂纹。这些裂纹的存在严重地影响合金的使用以及产品的质量和寿命。研究其形成的原因和影响因素,并提出预防措施,具有重要的意义。 一、形成焊接热裂纹的影响因素 1.合金元素及组织的影响 相似文献
11.
12.
13.
14.
15.
Effects of melt temperature and mold preheating temperature on the fluidity of Ca containing AZ31 alloys 总被引:3,自引:0,他引:3
The effects of melt temperature and mold preheating temperature on the fluidity of Ca containing AZ31 alloys were evaluated
under various casting conditions. The flow lengths of AZ31-xCa alloy melt increased with increasing the melt temperature due
to lower viscosity and longer time to fill the mold cavity. The increment of the flow lengths of AZ31-xCa alloy melt with
increasing the mold preheating temperature was not large due to large diameter of circular cross section of mold cavity. The
fluidity of AZ31-xCa alloy melts was affected more forcefully by melt temperature than by mold preheating temperature under
casting conditions used in this study. Also, the flow lengths of AZ31-xCa alloy melt were affected by grain size of primary
solid particles solidified during filling mold cavity and surface oxide film due to addition of Ca. 相似文献
16.
In this study, a rapidly solidified aluminum alloy was compared with beryllium copper and 6061 aluminum alloys in terms of their wear rates, hardness and performance as mold insert materials. A Vickers hardness measuring machine and a tribometer were used to determine the hardness values and wear rates of the materials. Three sets of mold inserts were made of these materials, and the insert surfaces and the molded plastic lens surfaces were characterized using a scanning electron microscope and a surface profilometer, respectively. The investigation results indicate that the BeCu alloy has the lowest wear rate, while aluminum 6061-T6 has the highest wear rate. Although the rapidly solidified aluminum alloy is not as hard as the BeCu alloy, the differences between their wear rates and hardness values are not as great as the differences between aluminum 6061-T6 and the BeCu alloy. The results also indicate that the rapidly solidified aluminum alloy performs much better than aluminum 6061-T6 in molding of plastic lenses and is comparable to the BeCu alloy. It is able to attain finer surfaces of the molded plastic lenses. This is an important finding, and this means that the rapidly solidified aluminum alloy can replace the BeCu alloy as a good mold insert material, because beryllium (Be) is a toxic element. The finding gives the industry a better choice for selection of mold insert materials. 相似文献
17.
目的 针对铝铜合金热裂敏感性高、难以进行金属型铸造的难题,研究其合金成分、铸造工艺、组织与性能的关系。方法 首先充分分析铸造铝铜合金的凝固机制与特点,在ZL205A合金基础上,设计了新型合金成分以及两种铸造试样模,经过熔炼、铸造与热处理,获得砂型铸造与金属型铸造试样,进行力学性能测试、组织分析,并观察试样的抗热裂性。结果 两种铸造试样都获得了较高的力学性能,铸态及T6态全部为等轴晶组织,成功避免了热裂问题,并提高了合金的力学性能;金属型铸造试制了油马达铸件。结论 证明了通过铝铜合金的成分优化设计,以及含钪复合细化剂的合理匹配,采用金属型铸造获得等轴晶组织,进而避免粗大枝晶组织,是克服热裂问题的关键,从而实现金属型铸造高强度铝铜合金。 相似文献
18.
The explicit microstructural evolution and electrochemical performance of value added palm kernel shell ash nanoparticle/A356 alloy composite produced by double layer feeding-stir casting method was studied. The composites were produced using 0 and 4 wt% palm kernel shell ash nanoparticle. X-ray diffractometer, transmission, scanning electron microscopes and electrochemical analyser were used for the analysis. It was observed that double layer feeding-stir casting method increases the wettiability of the palm kernel shell ash nanoparticle in A356 alloy and decreases the brittle intermetallic phase. Uniform distribution of the palm kernel shell ash nanoparticle in A356 alloy. The mismatch at the interface between the palm kernel shell ash nanoparticle and A356 alloy was 4.26 %. The Al-phase and the palm kernel shell ash nanoparticle were parallel in relationship along the interfaces. Dislocation structure at the interface was visible and coherent with regular arrangement of palm kernel shell ash nanoparticle. The corrosion resistance of the composite was higher than that of the alloy in simulated sea water. 相似文献
19.
吴俊峰 《理化检验(物理分册)》2012,(6):394-396,402
某2A12铝合金壳体在系统分离试验时发生耳片断裂失效,为分析其断裂原因对壳体耳片进行了化学成分分析、金相检验,断口分析以及能谱分析。结果表明:该壳体耳片断口为典型的木纹状断口,断裂起源于零件表面的未溶杂质化合物聚集处;导致其断裂的主要原因是壳体原材料挤压变形量不够,加之淬火加热温度不足,使材料显微组织中存在较多铸态枝晶网状不良组织和未溶化合物,降低了材料的强度和塑性。 相似文献