A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties

Powder metallurgy (PM) of titanium is a potentially cost-effective alternative to conventional wrought titanium. This article examines both traditional and emerging technologies, including the prod...

https://www.tandfonline.com/doi/pdf/10.1080/09506608.2017.1366003

Powder metallurgy of titanium – past, present, and future

Nanostructured (i.e., 1–200 nm grain size) and ultrafine-grained (i.e., 200–500 nm grain size) metals are of interest, not only as a result of their unusual combinations of physical and mechanical properties, but also because they can be readily synthesized using well-developed synthesis techniques. Cryomilling, i.e., mechanical alloying in liquid nitrogen, is representative of a class of synthesis techniques that attain the nanostructured state via severe plastic deformation. In this overview, published data related to cryomilled materials are reviewed and discussed with particular emphasis on cryomilling mechanisms; microstructure and thermal stability of cryomilled powders; primary consolidation and secondary processing methods; microstructural evolution during consolidation; and mechanical response of consolidated materials. The deformation behavior and the underlying mechanisms that govern cryomilled materials are discussed and compared with those of nanostructured materials processed via other methods, in an effort to shed light into the fundamental behavior of ultrafine-grained and nanostructured materials.

Cryomilled nanostructured materials: Processing and properties

Advances in metals and alloys for joint replacement

The morphological and microstructural changes during mechanical milling of Al powder mixed with 5 vol% nanoscaled alumina particles (35 nm) were studied. The milling was performed in a planetary ball mill under argon atmosphere for various times up to 24 h. The process was also conducted for Al and Al–5 vol% Al 2 O 3 (1 μm) powders to explore the role of reinforcement nanoparticles on the mechanical milling stages. The results showed that the addition of hard particles accelerate the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Meanwhile, the structural evolution during mechanical milling of the microcomposite powder occurred faster than that of the nanocomposite powder. The result of X-ray diffraction analysis by Williamson–Hall method determined that the so-called crystallite size and lattice strain of the Al matrix of nanocomposite are smaller than that of the microcomposite. Meantime, the particle size distribution and bulk powder density of the two composites were found to be rather equal after 20 h milling, but they were significantly different from those of the unreinforced Al. The mechanisms of mechanical milling for the reinforced and unreinforced Al powders are addressed with stressing on the role of alumina particles.

Structural evolution during mechanical milling of nanometric and micrometric Al2O3 reinforced Al matrix composites

Three similar varieties of pure Ti hydride-dehydried (HDH) powders were tested for the understanding of the variables that have an influence on the compaction process of Ti powders. The study shows that small differences in the characteristics of the powders lead to very different behaviours in the compaction stage. Compressibility curves, friction with the die walls and ejection forces are discussed in this study. The results are compared with a commercial iron powder as a reference to complete the discussion, as well as to show the enhancements and modifications that should be performed in Ti powders to design an optimized powder suitable for being pressed in an industrial process.

/pdf/study-of-compaction-and-ejection-of-hydrided-dehydrided-3lyfgsr464.pdf

Study of Compaction and Ejection of Hydrided-Dehydrided Titanium Powder

The development of new extraction processes to produce titanium in powder form leads Powder Metallurgy to an advantage position among the manufacturing processes for titanium. The cost reduction of base material, coupled with the economy of the powder metallurgy processes, give titanium industry the chance to diversify its products, which could lead to production volumes able to stabilise the price of the metal. This work reviews some of the Powder Metallurgy techniques for the manufacturing of titanium parts, and describes the two typical approaches for titanium manufacturing: ‘Blending Elemental’ and ‘Prealloyed Powders’. Among others, conventional pressing and sintering are described, which are compared with cold and hot isostatic pressing techniques. Real and potential applications are described.

http://digital.csic.es/bitstream/10261/53653/1/Rev.Met%2c47%2c2%2cGot.pdf

Introducción al procesado pulvimetalúrgico del titanio

Sintering of aluminum alloys is usually performed by the formation of a liquid phase. A liquid phase in 2xxx series alloys is formed from α+Al2Cu eutectic. In this work, the influences of trace elements like Sn or Pb, and the addition of a ceramic reinforcement, such as TiCN, on 2014 alloys are studied. Mechanical properties as well as a microstructural study show improved results.

2014 based MMCs: Properties improvement by (TiCN)p and trace additions

Electrochemical comparative study on corrosion behavior of conventional and powder metallurgy titanium alloys in physiological conditions

The objective of this study aims to the development of Fe-matrix composites with high carbide content to achieve properties between high-speed steels (HSS) and cemented carbides. Cemented carbides are harder and show higher wear resistance than HSS, but lower toughness. Besides, the substitution of Co or Ni for other binders is desirable due to the carcinogen character of these metals. In this work, a material constituted by an iron matrix and a 50 % wt of WC and TaC carbides is developed. High-energy milling has been used to obtain composite powders presenting a good bonding and homogeneous distribution of the carbides in the matrix. Those powders were characterised and compacted by die pressing. The green compacts were sintered at different temperatures, and properties like hardness and density were determined. Also, the wear behaviour was studied and microstructural analysis by SEM was carried out to complete the study.

/pdf/desarrollo-de-materiales-compuestos-tipo-cermet-de-matriz-fe-4ut2gl6sx2.pdf

Elisa Maria Ruiz-Navas

Papers

Study of Compaction and Ejection of Hydrided-Dehydrided Titanium Powder

Introducción al procesado pulvimetalúrgico del titanio

2014 based MMCs: Properties improvement by (TiCN)p and trace additions

Electrochemical comparative study on corrosion behavior of conventional and powder metallurgy titanium alloys in physiological conditions

Desarrollo de materiales compuestos tipo cermet de matriz Fe