In-situ development of Fe3C and TiC reinforcements during the mechanosynthesis of Cu–10Sn–15Ti/diamonds composite powders by high energy ball milling: Microstructural, thermal, and mechanical characterization

The development of iron and titanium carbides nanoparticles reinforcements during the mechanosynthesis Cu–10Sn–15Ti/diamonds composite powders from a mixture of blended Cu/Sn/Ti powders and synthetic diamonds (10 wt.%) was studied in this work. The analysis of the microstructure evolution showed that mechanical alloying performed at high-energy ball milling (600 rpm) allows developing different metastable phases depending on the SA content and milling time. For 3 wt.% of SA, XRD patterns revealed a metastable Cu(Sn) solid solution is produced after 5 h of MA while Fe2.939O4, FeTiO3 and TiH0.66 nanophases were formed for milling times higher than 15 h as a result of degradation of the SA in form of gaseous products (CO, CO2, H2, and lighter hydrocarbons (HC's)). XRD confirm that the release of these gases, along the SA degradation, and high carbon content carbon favors the carbothermic reduction of Fe2.939O4 for producing amorphous Fe3C nanoparticles at low-temperature thanks to the high-energy transferred in each impact during the MA process. For 1 wt.% of SA, XRD patterns showed the formation of Cu (Ti, Sn), from the very beginning of the process (5 h), is accompanied by the release of carboxyl groups (COOH) and crystallization of long heptadecane chains, CH3(CH2)15CH3. The high boiling point of this heptadecane chains and the low Fe released during milling, produces a lower content of amorphous Fe3C nanoparticles. DSC and SAED patterns performed in the mixture of both alloyed powders after heating up to 1000 °C showed the carbothermic reduction of FeTiO3 for producing TiC nanoparticles takes place preferably when a 3 wt.% of SA is used. In both cases, the resulting alloyed powders are composed by a mixture of crystalline Cu13.7Sn + Fe + Fe3C + C + TiC phases with an Fe, and Fe3C and TiC content lower in the case of the powders processed with 1 wt.% SA. The development of this dissimilar Fe3C and TiC content produces the mixture with 3 wt.% of SA shows a higher stiffness. [Display omitted] •Optimization of stearic acid content for the design of reinforced brazing alloys.•Activation of the carbothermic reductions of Fe3O4 & FeTiO3 at low temperatures.•Stiffness improvement in the Cu-10Sn-15Ti/diamond mixture with the development in-situ of Fe3C.•Low-temperature TiC development for an increased wettability of diamond interface.