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The effect of tensile stress on thermal microstructure evolution of Ω phase in an AI-Cu-Mg-Ag alloy with high Cu/Mg ratio and higher Ag content was investigated by transmission electron microcopy (TEM) .The samples were aged at 200 ℃ for 1 h (T6 condition), then thermal exposed at 250 ℃ for 100 h with and without a tensile stress (130 MPa), respectively. The results indicate that Ω precipitates uniformly disperse in the matrix as a major precipitate after artificially aging at 200℃ for 1 h (T6 condition). Exposed at 250℃ for 100 h without stress, Ωprecipitates dissolve dramatically. Whereas, during stress exposure they coarsen unexpectedly rather than dissolve into matrix. It can be deduced that the stress retards the redissolution of Ω phase. 相似文献
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The technology of cold pressure welding was adopted to achieve the bonding of Al/Cu(limited soluble and forming compounds),Ag/Ni(hardly mutual soluble),and the relative state of interface was tested by HREM.The results indicate that stable interface is always corresponding to the low interfacial energy value;the stable interface is not coherent but partly-coherent because of the twisting of grain boundary caused by pressure,meanwhile existing dislocation.Namely,the interfacial match and other states under the condition of cold pressure welding are different from the situation that under the condition of thermal action.Moreover,theoretical analyses and calculation on the base of thermodynamics,crystallogeny ,solid physics etc,were discussed. 相似文献
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教育部、卫生部适时提出了在全国医药学各专业实施"卓越医师"教育的理念。要全面提升医科学生的综合能力,就应该坚持教育以育人为本,以学生为中心,以教师为主导,以各种不同的教学手段为导学,培养学生的逻辑思维能力、实际动手能力、分析问题解决问题能力。《医用物理学》是大一第一学期的必修课,应当成为"卓越医师"教育的基础工程。 相似文献
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Base metals of domestic pipeline steels were used to study the effect of Mn on corrosion properties of SSCC( Sulfide Stress Corrosion Cracking), and welds were carried out to study the effect of MnS on corrosion properties of HIC ( Hydrogen Induced Cracking) both in solutions with wet hydrogen sulfide ( H2 S ). They were respectively conducted by referring to the standards of SSCC and HIC. Testing results revealed that with the increase of content Mn, the resistance of SSCC will be decreased, from the point of metallurgic view, and it is Mn element not C element to lead to the testing results of SSCC. Meanwhile, even under the condition without inclusions MnS, HIC in welds still occurred. That is to say, MnS is not necessary for HIC, the presence of local banded structures in which Mn and P are inclined to aggregate cause to the phenomena of HIC. 相似文献
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Oblique Y-groove cracking test of the welding cold cracking susceptibility of domestic X-70 pipeline steel 总被引:1,自引:0,他引:1
“Gas Transmitting From West to East Project“ is significant.it should ensure the welding quality and safety of pipeline.The task is very arduous to guarantee the quality of the projcet in the condition of long line.complex weather and geolgy features.in this paper,the welding cold cracking susceptibility of domestic X-70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline,was studied by means of oblique Ygroove cracking test.The crack ration of surface and section was tested under the conditions of different welding materials and preheat temperature.The thickness of plate stell was 14.7mm and 10.3mm.The results reveal that X-70 pipeline steel has good crack resistance.The research has important value for the construction of large-scale pipeline engineering and the application of domestic X-70 pipeline steel. 相似文献
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利用透射电镜、SEM形貌观察、剩余强度的测定等试验手段,研究了AlCuMgAg铝合金在欠时效状态下的高温持久对合金的微观组织和力学性能的影响。结果表明,165℃×4h欠时效状态的合金在高温高压持久(200℃、220MPa)条件下,强度逐渐增加,持久时间为20h时,强度达到最大值,而后缓慢下降;持久时间为100h的断裂仍为韧性断裂,只是无析出带的宽度增加。 相似文献
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以月桂酸为相变材料,膨胀珍珠岩为载质,利用真空吸附法制备出月桂酸/膨胀珍珠岩复合相变材料(LA/EP-PCMs)。通过FT-IR、SEM、DSC、TGA对LA/EP-PCMs的微观结构、相变温度、相变潜热、热稳定性进行表征。结果表明:月桂酸能较好地吸附在膨胀珍珠岩孔隙内,它们之间的化学相容性良好。LA/EP-PCMs中月桂酸饱和含量为65%,此时其相变温度为41.3℃,热焓为110.1J/g。将5%的纳米石墨纤维(NGF)作为添加剂加入到LA/EP-PCMs中,其导热系数由0.09 W/(m·K)提高到0.16 W/(m·K),增长了77.7%。熔融凝固实验表明:掺入NGF将改善复合相变材料的蓄放热能力,其强化导热机理是在相变基体外表面和内部形成了导热网络。 相似文献