Investigation on the interface of Cu/Al couples during isothermal heating

The evolutionary process and intermetallic compounds of Cu/Al couples during isothermal heating at a constant bonding temperature of 550°C were investigated in this paper. The interfacial morphologies and microstructures were examined by optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results suggest that bonding is not achieved between Cu and Al at 550°C in 10 min due to undamaged oxide films. Upon increasing the bonding time from 15 to 25 min, however, metallurgical bonding is obtained in these samples, and the thickness of the reactive zone varies with holding time. In the interfacial region, the final microstructure consists of Cu9Al4, CuAl, CuAl2, and α-Al + CuAl2. Furthermore, these results provide new insights into the mechanism of the interfacial reaction between Cu and Al. Microhardness measurements show that the chemical composition exerts a significant influence on the mechanical properties of Cu/Al couples.

Microstructural characterization of Cu/Al composites and effect of cooling rate at the Cu/Al interfacial region

Cu/Al composites are of vital importance in industrial applications because of their numerous advantages.The influence of bonding temperature and cooling rate on the microstructure and morphology of Cu/Al composites was investigated in this paper.The interfacial morphology and constituent phases at the Cu/Al interface were analyzed by optical microscopy and field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy.The results indicate that effective Cu-Al bonding requires a higher bonding temperature to facilitate interdiffusion between the two metals.The microstructural characteristics are associated with various bonding temperatures,which impact the driving force of interdiffusion.It is observed that cooling rate exerts a significant influence on the morphology and amount of the intermetallic compounds at the interfacial region.Meanwhile,microhardness measurements show that hardness varies with the bonding temperature and rate of cooling.

Wear behavior of bainite ductile cast iron under impact load

The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces' micro-hardness profiles. Scanning electron microscopy(SEM) and X-ray diffraction(XRD) were used to observe the worn surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20°C, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20°C is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity(TRIP) phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.

Modeling the austenite-ferrite transformation in microalloyed steel P510L

Based on experimental results, the transformation kinetics and cooling characteristics of low-carbon steel were analyzed and modeled to quantitatively link the operational parameters of a process with the properties. From the continuous cooling transformation results, comparisons of the start temperature of austenite-ferrite transformation among three models were analyzed, and the optimal lnk and n, which are the parameters in the Avrami equation, were determined by applying two regression models at different cooling rates. The transformation kinetics during continuous cooling was determined. Furthermore, reasonable agreements between experimental results and predictions were obtained, which can demonstrate the rationality of the established models.

Adverse effect of niobium and boron on hot deformation behavior of sulfur-containing steel

The hot deformation behaviors of sulfur-containing gear steel 20MnCr5 containing three different contents of Nb and B(0,0.021%Nb,and 0.024%Nb-0.0022%B)were investigated.Hot compression and tenssion tests were carried out by Gleeble3800 at the austenite region from 850 to 1150℃and the adverse effects of Nb and B were analyzed by the fracture,microstructure and precipitate observations.Hot compression tests showed that the proportions of instable area in hot processing maps of 0.021%Nb and Nb-B steels were higher and the deformability of Nb free steel was better.The tensile deformation experiments showed that the reduction areas of Nb free,0.021%Nb and Nb-B steels were 92%-99%,84%-98%and 67%-97%,respectively.The addition of Nb or Nb and B inhibited the dynamic recrystallization during hot deformation,and consequently,more deformed grains were then formed in 0.021%Nb and Nb-B steels thus to obtain the microstructure with worse uniformity and then deteriorate the deformability.In addition,the interaction between inclusions and microalloyed elements was also significant.NbC particles of 0.021%Nb and Nb-B steels dynamically precipitated during deformation and precipitated together with MnS thus to worsen the deformability,resulting in the decrease of reduction area.

Abrasive Wear Behavior and Mechanism of High Chromium Cast Iron

The abrasive wear behavior of high chromium cast iron(containing 12.9mass%chromium)austenitized at1 050 ℃for 2hand austempered in salt bath at 320℃for 4hwas evaluated.Abrasive wear was performed using alumina abrasive under four different loads,namely 50,100,150,and 200 N,for 36 000 cycles.The worn surfaces and wear debris were analyzed by scanning electron microscopy,laser confocal microscopy and X-ray diffraction.Microhardness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces.Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation after tests,for small amounts of retained austenite could be detected by X-ray diffraction.In addition,there is a close relationship between wear mechanism and test load.Under the condition of lower test load,the wear mechanism is an uninterrupted and repeated process,during which matrix is cut at first and then fine carbides flake off.As to higher test load,scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.

Immunotherapy for hepatocellular carcinoma: the force awakens in HCC?

Systemic therapy for hepatocellular carcinoma (HCC) has been disappointing. The only drug approved by Food and Drug Administration recently has been sorafenib. Sorafenib has modest benefits with a low response rate and an improvement in time to progression of only 2-3 months. Multiple randomized trials, which compare the new agent to sorafenib as either first line or second line therapy, have been negative, showing no improved clinical benefit. Recently, in a large phase Ⅲ randomized trial, regorafenib has shown superiority to placebo as a second line treatment for HCC. However, this drug has multiple side effects and is not well tolerated by many patients. The clinical benefit is also modest. Clearly, new approaches to treat advanced HCC are still needed. There is data showing that HCC is immunogenic and the immune system can be stimulated to attack these cancer cells. This article will briefly review immunotherapy as a promising treatment for HCC.