Commercially pure titanium (CP-Ti) has received a great deal of attention in medical applications. Improvement of its mechanical properties plays a key role in enhancing the biomechanical compatibility of Ti implants, leading to avoid revision surgeries. Emerging advanced manufacturing technologies such as selective laser melting (SLM) is providing an ideal platform for producing components with almost no geometric constraints and is economically feasible down to a batch size of one. This study presents the results of using SLM to produce CP-Ti parts starting from powder with a wide grain size range up to 100 μm. Accurate manipulation of SLM manufacturing parameters were applied to produce nearly full dense (>99.5%) CP-Ti parts without any post-treatments. Compared with the properties of those manufactured by traditional processing technologies, the microhardness, compressive, and tensile strengths of SLM-processed CP-Ti parts have been improved to 261 Hv, 1136 MPa, and 757 MPa, respectively, due to the formation of refined martensitic α′ grains during SLM. The optimal manufacturing parameters could enhance the strength and hardness of CP-Ti and yet maintaining the ductility of titanium. Fractography study of the tensile-failed SLM-processed specimens showed that incompletely melted particles and porosities caused early fracture in porous sample. Mixture of dimples and minor quasi-cleavage facets covered most fracture surface of full dense sample.

Manufacture by selective laser melting and mechanical behavior of commercially pure titanium

Nanostructure formation mechanism of α-titanium using SMAT

Ultrafine-grained (UFG) Ti samples have been prepared using equal channel angular pressing followed by cold rolling and annealing. The deformation behavior of these materials, including strain hardening, strain rate dependence of flow stress, deformation/failure mode, and tensile necking instability, have been systematically characterized. The findings are compared with those for conventional coarse-grained Ti and used to explain the limited tensile ductility observed so far for UFG or nanocrystalline metals.

Deformation behavior and plastic instabilities of ultrafine-grained titanium

Strain hardening of titanium: role of deformation twinning

Microstructural based models for bcc and fcc metals with temperature and strain rate dependency

http://ceam.ucsd.edu/documents/papers/mechanicalproperties.pdf

Mechanical properties and deformation mechanisms of a commercially pure titanium


 Stainless steel with high surface quality is required in many industries and chemical mechanical polishing can achieve both local and global planarization of the substrate surface. However, it is difficult to realize both high material removal rate and high surface quality by a single step polishing. In this regard, a two-step polishing process, coarse polishing with α-Al2O3 abrasives first and then fine polishing with silica abrasives, was proposed to solve the trade-off between material removal and surface quality. The effects of pH (1~12) and H2O2 (0~0.5wt%) on the polishing of 304 stainless steel disk (area ~6.7 cm2) were systematically studied and CMP mechanism of stainless steel was discussed. The results indicated that, at pH 4, with the addition of 0.01wt% H2O2, the surface roughness of stainless steel was successfully reduced from 0.702 μm to 44.6 nm (the first step using α-Al2O3 abrasives) and 1.61 nm (the second step using silica abrasives). Finally, an ultra-smooth surface was obtained with decent material removal rate.

W.G. Guo

Papers

Mechanical properties and deformation mechanisms of a commercially pure titanium

Two-Step Chemical Mechanical Polishing of Stainless Steel