Mechanical Alloying of Titanium-Base Alloys

Application of mechanical alloying to titanium-base alloys is a recent development. A wide range of terminal phases and those based on titanium aluminides (both Ti₃Al and TiAl) have been examined and it has been shown that synthesis of metallic phases can be achieved by mechanical alloying. The phases so synthesized include solid solutions, intermediate crystalline phases, amorphous phases, and nanostructured materials. It has also been shown that the resistance to coarsening of both the grains and the dispersoids in mechanically alloyed Ti₃Al based alloys is much higher than in rapidly solidified alloys. The review concludes with some thoughts on future developments in this exciting area.     

Influence of Process Variables on the Structure of Mechanically Alloyed Ti_3Al-base Intermetallics

During mechanical alloying variables such as the type of mill,milling intensity,milling time,milling at-mosphere and ball-to-powder weight ratio(BPR)affect the morphology and constitution of the product.The effect of milling time,milling atmosphere and BPR on the nature of the product formed in mechanical-ly alloyed pure Ti and blended elemental binary Ti-Al,and ternary Ti-AI-Nb alloy powders was described.Mechanical alloying of pure titanium results,after long milling times,in the formation of an fcc phase.Inthe binary alloy,a solid solution of aluminum in titanium,an amorphous phase,and a fcc phase form withincreasing milling time.The fcc phase,which is probably a result of TiN formation,occurs more rapidly inair or nitrogen than in an inert atmosphere.Formation of the B2 phase in the ternary alloys depends bothon alloy composition and the milling atmosphere,with 100％ formation in all atmospheres in Ti-25Al-25Nbbut not in Ti-24Al-11Nb,and an inert atmosphere favoring formation.The times required for the formationof the different phases decrease as the BPR increases;but their sequence is unaffected.Based on this infor-mation,“milling maps”which describe phase formation as a function of the BPR and milling time are con-structed.Contamination from the milling balls increased as the BPR was increased.     

Mechanical Alloying

This paper reviews state-of-the-art mechanical alloying (MA) technology, a technique which is being used to produce attractive property combinations in nickel- and aluminum-base materials. Other applications include coatings, supercorroding alloys and, to a minor extent, production of normally difficult to produce alloy combinations. Even though mechanical alloying is already a commercially viable process for producing materials with enhanced behavior, many facets of this processing approach are still in the embryonic stage and warrant more indepth exploration.     

Determination of Inorganic Elements in Teas Using Inductively Coupled Plasma Optical Emission Spectrometry and Classification with Exploratory Analysis

Multivariate optimization was employed to obtain the best conditions of the inductively coupled optical emission spectrometer (ICP OES) (nebulization gas flow rate of 0.47 L min^?1 and applied power of 1.36 kW) for the determination of Al, Ba, Ca, Cu, Fe, K, Mg, Na, and Mn in 27 green tea samples. In the hierarchical cluster analysis, it was possible to observe the formation of five different groups (imported Japanese samples, samples without specifications, organically cultivated samples, samples in capsules, and ready-to-drink iced tea samples) besides the separation according to brand. In the principal component analysis we verified that the first four main components explained 99.98 % of the total variance. The ICP OES technique and the exploratory analysis were shown effective tools that can be used jointly in the quality control and classification of green tea samples.