Effects Of Different-sized TiC Particles On Microstructures And Properties Of HT200

Gray cast iron is widely used in the mechanical industry especially automotive structural parts and machine tools due to its excellent casting formability, good corrosion resistance and abrasion resistance, high hardness, easy to control the quality and low cost.However, with the rapid development of technology, new requirements to its properties emerges. Especially, with the trend towards lighter mass and higher power in the auto industry, the requirement of thin-section and high-strength is higher and higher.On the basis of the theoretical calculation, the lattice mismatch between Ti C and austenite is less than 15%, Ti C ceramic particles can act as the crystal nucleus of primary austenite during the solidification, which increase the amount of primary austenite and obtain the complex space net structure. It affect the morphology, size,amount and distribution of graphite in gray cast iron to improve the mechanical properties of gray cast iron.The copper matrix composites reinforced by in-situ Ti C particles with different size were fabricated successfully by the combustion synthesis and hot press consolidation method.The effects of the Ti C particles size and contents on the microstructures and mechanical properties of the composites were studied. The main results of the study are as follows:1) It reveals the influence laws of different carbon source, as well as different C/Ti ratio and Al contents on reaction products and Ti C ceramic particles size:The micron-sized Ti C particles can be fabricated when carbon source is carbon black, the ratio of C/Ti is1.0 and Al content is 40 vol.%,the submicron-sized Ti C particles can be fabricated. when carbon source is CNTs with average diameter of 20 nm to 30 nm,the ratio of C/Ti is 1.0and Al content is 60 vol.%,The nano-sized Ti C particles can be fabricated. when carbon source is CNTs with average diameter of 20 nm to 30 nm, the ratio of C/Ti is 1.0 and Al content is 80 vol.%.2) The addition of nano-sized, submicron-sized and micron-sized Ti C particles can improve the tensile strength of the gray cast iron.The tensile strength of gray cast iron samples increase with the decrease of the Ti C ceramic particle size. The tensile strength of gray cast iron samples increase firstly and then decrease with the increase of the Ti C content. At room temperature, the tensile strength of 0.5 wt.% nano-sized Ti C reinforced gray cast iron composites increase by 50.4% compared with the pure grey cast iron.3) It reveals the strengthening mechanism of Ti C ceramic particles in gray cast iron: Ti C ceramic particles can act as the crystal nucleus of primary austenite during the solidification, which increase the amount of primary austenite to obtain the complex space net structure. This structure has limited the eutectic reaction in gray cast iron and creates conditions to obtain the fine, bending and uniform graphite morphology.Meanwhile, Ti C ceramic particles can promote the genesis and development of eutectoid transition in gray cast iron to obtain the pearlite matrix with smaller lamellar space. And the strengthening effect is particularly obvious with the decrease of the Ti C ceramic particle size.