Cu_(64)Zr_(36)非晶合金粉末的高温氧化行为

通过气体雾化法制备Cu_(64)Zr_(36)非晶合金粉末。采用XRD、DSC、TGA、SEM和TEM等测试手段研究Cu_(64)Zr_(36)非晶合金粉末在内部因素(粉末粒径)和外部因素(氧化温度和氧化时间)影响下的高温氧化行为。分析非晶合金粉末的氧化动力学、氧化物组成、表面形貌和显微组织演变。实验结果表明,Cu_(64)Zr_(36)非晶合金粉末氧化后表面形成多层氧化物,氧化层主要成分为t-ZrO_(2)、m-ZrO_(2)、Cu_2O和CuO。氧化动力学遵循双级抛物线速率定律。氧化过程以O离子向内扩散和Cu离子向外扩散控制。热力学分析表明,随着粉末粒径的减小,氧化反应的吉布斯自由能变大,导致粒径更小的粉末氧化更为迅速且完全。

Processing map and hot deformation behavior of squeeze cast 6082 aluminum alloy

The hot deformation behavior and microstructure evolution of 6082 aluminum alloy fabricated through squeeze casting(SC)under different pressures were studied.The alloy was subjected to hot compression tests and 3D hot processing maps were established.The microstructure evolution was studied by optical microscope(OM),scanning electron microscope(SEM),and electron backscattered diffraction(EBSD).It is found that more dynamic recrystallization(DRX)grains are generated during the deformation of the specimen fabricated under higher SC pressure.At high temperature the effect of SC pressure on microstructure evolution weakens due to the dissolution of second phase particles.In addition,uneven second phase particles in specimens fabricated under higher SC pressure compressed with low temperature and middle strain rate would result in flow localization instability.Finally,the optimum deformation conditions for the 6082 aluminum alloy fabricated by SC were obtained at the temperatures of 430−500℃ and the strain rates of 0.01−1 s^(−1).

EXPRESSION AND SIGNIFICANCE OF SURVIVIN mRNA IN LUNG CANCER TISSUE MICROARRAY DETECTED BY FISH

Objective To investigate the expression of Survivin mRNA in lung cancer tissue microarray （TMA） by fluorescence in .situ hybridization （FISH） method, and determine the role and significance of it in lung cancer genesis and progress. Methods The expression of Survivin mRNA was detected by FISH method and TMA technology. Fifty-four cases of lung cancer and 10 cases of normal lung tissue were examined. Survivin mRNA was expressed in 66.7% （36/54） of lung cancer; the positive ratio of lung cancer was significantly higher than that of normal lung tissue （0/10;X^2= 15.238, P 〈 0.05）. The positive ratio of Survivin mRNA was significantly higher in poor differentiated cancer （20/24, 83.3% ） than moderate and well differentiated cancer （16/30, 53.3%; X^2 = 5.40, P 〈 0.05）. The positive ratio of Survivin mRNA was significantly higher in group with lymph node metastasis （27/32, 84.4%） than without lymph node metastasis （9/22, 40.9%; X^2= 11.084, P 〈 0.05）. The positive ratio of Survivin mRNA was significantly higher in stage Ⅲ-Ⅳ（12/13, 92.3%） than stage Ⅰ- Ⅱ （24/41,58.5%; X^2=5.066, P〈 0.05）. Conclusion Survivin mRNA highly expresses in lung cancer, which is related to the progress and malignant behavior. Survivin may play a promoting role in lung cancer genesis and progress and provide a basis for estimating prognosis and treatment.

Preparation of tungsten-particle-reinforced Zr-based bulk metallic glass composites by two-step spark plasma sintering:microstructure evolution,densification mechanism and mechanical properties

A new two-step spark plasma sintering(TSS)process with low-temperature pre-sintering and high-temperature final sintering has been successfully applied to prepare the tungsten-particle(Wp)-reinforced bulk metallic glass composites(Wp/BMGCs).Compared to normal spark plasma sintering(NS),the densification rate and relative density of Wp/BMGCs can be improved by selecting TSS with appropriate sintering pressure in the low temperature pre-sintering stage.However,the compressive strength and plastic strain of 30%Wp/BMGCs prepared by TSS are both higher than those of the samples prepared by NS.The TSS process can significantly enhance the compressive strength of 30%Wp/BMGCs by 12%and remarkably increase the plastic strain by 50%,while the trend is completely opposite for 50%Wp/BMGCs.Quasi-in situ experiments and finite element simulations reveal that uneven temperature distribution among particles during low-temperature pre-sintering causes local overheating at contact points between particles,accelerating formation of sintering neck between particles and plastic deformation of Wp.When the volume fraction of Wp is low,TSS can improve the interface bonding between particles by increasing the number of sintering necks.This makes the fracture mode of Wp/BMGCs being predominantly transgranular fracture.However,as the volume fraction of Wp increases,the adverse effects of Wp plastic deformation are becoming more and more prominent.The aggregated Wp tends to form a solid"cage structure"that hinders the bonding between particles at the interface;correspondingly,the fracture behavior of Wp/BMGCs is mainly dominated by intergranular fracture.Additionally,reducing the sintering pressure during the low-temperature pre-sintering stage of TSS has been shown to effectively decrease plastic deformation in Wp,resulting in a higher degree of densification and better mechanical properties.