In this paper, densification of in-situ copper-niobium carbide composite using cold pressing technique was addressed. Mixtures of Cu-20vol%NbC powder were prepared by two methods.
In first method, a mixture of Cu-15.79wt%Nb-2.04wt%C powder was milled at 400 rpm for 35 hours in a planetary mill. In second method, Cu and commercial NbC powder was mixed at 100 rpm for 2 hours in a jar mill. Then, both powders were pressed at different pressure (i.e. 350 MPa, 450 MPa, 550 MPa and 650 MPa) and sintered at 900 o C for 1 hour. Sample of in-situ and ex-situ Cu-20vol%NbC composite were characterized for density, hardness, phase formation by x-ray diffraction analysis and microstructure by scanning electron microscope. Xray diffraction analysis showed that NbC phase was formed in the in-situ processed sample. Hardness of in-situ processed copper composite was higher than that of the ex-situ processed copper composite due to good interface between coper matrix and niobium carbide reinforcement particle as well as distribution of finer niobium carbide particles in copper matrix. Sintered density of in-situ composite is lower than density of ex-situ composite beacuse of work hardening of the Cu-Nb-C mixture powder during powder to ball collision. Density and hardness of the in-situ and ex-situ Cu-20vol%NbC composites increase with the increase in compaction pressure as porosity is eliminated at higher compaction pressure.
Aluminum foams were fabricated by sintering dissolution process (SDP) using sodium chloride (NaCl) as space holder. The compositions of space holder, used in this study were 40 and 60 wt. % with different dissolution times; 1, 2 and 3 h. The effect of different dissolution times on compressive behavior and energy absorption of foams were evaluated. The result showed that by increasing space holder and dissolution times, energy absorption capability increases. For aluminum foam contains 60 wt. % NaCl, longer dissolution times resulted in thinner cell wall and cell structure become more unstable which lead to lower plateau region.
Commercially pure titanium (cp-Ti) and Ti-6Al-4V alloy have emerged as excellent candidates for use as biomaterials in medical implants due to their high strength-to-weight ratio and biocompatibility. β-type Ti alloys composed of non-toxic metallic elements such as niobium (Nb) have been extensively studied in order to resolve the issue of a high elastic modulus and toxicity of certain elements, particularly in Ti-6Al-4V alloy. Titanium hydride (TiH2) has recently received a lot of attention due to its densification, oxidation levels, and material costs. Powder metallurgy combined with mechanical alloying has become an attractive route for producing near-net shape components of Ti-based alloys, mainly where porosity control and better homogeneity are required. This review aims to create a platform for investigating the feasibility of producing Ti from TiH2 via a dehydrogenation process. The dehydrogenation behaviour of TiH2 is affected by variables such as sintering condition, alloying element, and particle size. The review revealed that TiH2 decomposition occurs at various temperatures (400 °C to 800 °C), resulting in the formation of several sequences of phases. Although the dehydrogenation process was unaffected, the addition of alloying elements was found to change the starting and ending temperatures of the reactions. The use of vacuum accelerates the dehydrogenation process more than argon flow. TiH2 powder with smaller particle size, on the other hand, eliminates hydrogen faster than larger ones due to the larger surface area exposed. This review also looks at the best processing conditions for getting a high concentration of β phase in Ti-Nb alloys. β-type titanium alloys with a low elastic modulus (10-40 GPa) similar to human bone are a potential strategy for reducing premature implant failure.
Considering the necessity for a biodegradable implant alloy with good biocompatibility and mechanical strength, dual ceramic particles of HAP and Al2O3 were added to Mg-Zn alloy to produce a new hybrid composite using powder metallurgy. The paper reports the mechanical and corrosion behaviour of Mg-Zn/HAP/Al2O3 hybrid composites containing variable wt.% HAP and Al2O3 with 15 wt.% total ceramic content. The powders of Mg, Zn, Al2O3 and HAP were milled in a high-energy ball mill, and then compacted under 400 MPa and sintered at 300 °C. Density and compression strength increased with increasing Al2O3 content. HAP facilitated weight gain in Hanks balanced salt solution due to deposition of an apatite layer which promoted anodic behaviour with higher corrosion resistance. A hybrid composite of Mg alloy with 5 wt.% Al2O3 and 10 wt.% HAP displayed 153 MPa compressive strength, 1.37 mm/year corrosion resistance and bioactivity with a CA:P ratio of 1:1.55 and appears to be the most promising biodegradable implant material tested.