Solidification microstructures of Al-Zn-Mg-Cu alloys prepared by spraydeposition and conventional casting methods

High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Secondary phases in the microstructures of the alloys prepared by spray deposition and conventional cast were examined. The results indicate that under the conventional casting condition, the microstructure of the alloy revealed the presence of coarse Al/Mg（ZnCu）2 eutectic phases, and the spray deposited process causes an obvious modification in size, morphology, and distribution of secondary phases in the microstructure as well as reduction of segregation. The superior microstructure of the spray-deposited Al-Zn-Mg-Cu alloy was attributed to the high cooling rate, and associated with the rapid solidification process.

Microstructure characteristics of Ni-43Ti-4Al-2Nb-2Hf alloy prepared by conventional casting and directional solidification

To further investigate the microstructure characteristic and solidification mechanism,so as to provide knowledge for the microstructure control of a NiTi-Al based high-temperature structural material,the microstructure of Ni-43Ti-4Al-2Nb-2Hf(at.%)alloy ingots prepared by conventional casting(arc-melting)and directional solidification (DS)at various drawing velocities(2 mm·min -1 ,18 mm·min -1 ,30 mm·min -1 and 60 mm·min -1 ,respectively)was investigated by means of electron probe microanalyses.Experimental results reveal that the microstructures are composed of NiTi matrix phase,β-Nb phase and Ti 2 Ni phase for samples obtained by both conventional casting and DS.Conventional casting has an equiaxial structure,while DS has a slender and acicular cellular structure which grows along the[001]orientation preferentially.Small amounts of whiteβ-Nb phase and black Ti 2 Ni phase co-exist at the grain boundaries or intercellular regions.With an increase in drawing velocity,the NiTi matrix phase is inclined to grow along(100)and(200)crystallographic planes,and the cellular arm spacing reduce gradually, but the directionality of the solidified structure weakens significantly.The homogeneous dispersion ofβ-Nb phase and the decrease of Ti2Ni phase in DS samples are beneficial to improving the mechanical properties.Solidification mechanism analysis indicates that the dark grey NiTi matrix phase initially precipitates from the liquid phase,and then the divorced eutectic reaction takes place,which produces the light gray matrix phase andβ-Nb phase.Finally, the peritectic reaction happens,which generates the black Ti2Ni phase.The complete solidified path of the alloy is L→NiTi+L→NiTi+β-Nb+L→NiTi+β-Nb+Ti 2 Ni.

Patients’perspectives on the conventional synthetic cast vs a newly developed open cast for ankle sprains

BACKGROUND Orthopedic physicians typically apply a cast to immobilize a body part that has been injured.There have been no significant structural changes or advances in synthetic casts since the development of the modern cast.The Opencast®is a recently developed type of cast that allows ventilation and direct visual inspection of the skin to avoid cast-related complications.Although this novel cast appears to have more benefits than the conventional synthetic cast,its clinical efficacy and advantages have not been established.AIM To investigate the clinical efficacy and advantages of the newly developed Opencast®based on patients’perspectives in those with ankle inversion injury.METHODS A specifically designed questionnaire consisting of 19 items was used to compare patients’opinions and concerns of the Opencast®and the conventional synthetic cast.The items were focused on subjective patient satisfaction,discomfort,and adverse effects while wearing the cast.Patients with an ankle inversion injury diagnosed as a high-grade ankle sprain were enrolled.The subjects were randomized and instructed to fill the questionnaire after wearing a synthetic cast or an Opencast®for 2 wk.They were then required to fill the questionnaire again,after switching to the alternative type of cast for 2 more weeks.RESULTS A total of 22 subjects participated in the study.The synthetic cast appeared to be more rigid and stable than the Opencast®,but there was no significant difference in the amount of pain relief.The likelihood of adverse effects when wearing the synthetic cast was significantly higher.Patient satisfaction tended to be rated higher after wearing the Opencast®.Opencast®showed more subjective vulnerability than the synthetic cast,but there was no significant difference in the redo rate.Patients were more anxious about removal of the synthetic cast than of the Opencast®.CONCLUSION The results indicate that the Opencast®could replace the conventional synthetic cast as it offers increased patient satisfaction,which would in turn increase compliance to treatment.

Casting of aluminum-copper based alloy by controled difusion solidiication

A quaternary alloy(Al-5.0Cu-0.35Mn-0.25Ti, wt.%), having a similar chemical component with ZL205A, was prepared using a controlled diffusion solidification(CDS) process and a conventional casting process. The effect of the casting process on microstructure and hardness was investigated. The grain morphology and casting defects of the alloy prepared via the conventional casting and CDS were observed and compared at various pouring temperatures. Results show that the CDS process can alleviate the hot tearing defects and reduce the density of porosity, while getting rid of the riser that is generally used for feeding during conventional casting. Structure observations show that the grain morphology of the conventional cast alloy is mainly dendritic, and the grain size decreases when the pouring temperature is decreased, while the CDS cast alloy consists of a large number of spherical grains, which can decrease the thermal cracking tendency and segregation defect, and enhance the hardness of the alloy.

The Convention of Die Casting Industry

The 8th China International Diecasting Congress & Exhibition June 17-22,2012 Shanghai Rhea Lakeview Hotel Shanghai New International Expo Centre(SNIEC) Organized by the Foundry Institution of Chinese Mechanical Engineering Society(FICMES) and the Productivity Promotion Center of Foundry Industry of China,the 8th China International Diecasting Congress&Exhibition is to beheld on June 17-22,2012 in Shanghai.This convention will providean opportunity for the diecasting professionals from China and the rest of the world to meet and discuss frontier technical development indie casting industry。