Research on Machinability of Particle Reinforced Titanium Matrix Composites
Author:Huan Hai Xiang
Supervisor:xu jiu hua
Particle reinforced titanium matrix composites(PRTMCs)have become a research focus of the advanced structural materials due to its potential to replace some titanium alloys in the aerospace and automobile application.However,the tough matrix and the ceramic reinforcements featuring high hardness and high brittleness which make PRTMCs difficult to cut;hence,some undesirable results,e.g.severe tool wear and poor surface quality,are generally countered when cutting such kind of materials.The paper mainly investigates the chip formation behavior,the tool wear mechanism and the machined surface characteristics in the turning process of PRTMCs.The milling features of PRTMCs are also discussed.The main researches involved in this thesis are as follow:(1)In order to understand the dynamic mechanical performance of PRTMCs,Hopkinson pressure bar tests are conducted with the operating temperature,strain rate and reinforcement volume fraction.The temperature range at which a desirable tool life can be achieved is optimized.The effects of the cutting speed on cutting force and temperature levels are analyzed.The chip patterns are characterized in both the macro-and micro-perspective.The serration degree and concentration shear frequency of the chips generated are also studied.In addition,the role of the cutting parameters in the chip formation process is explored by using the explosive quick-stop device.(2)Friction experiments are carried out to study the frictional behavior between PCD cutting tool and PRTMCs material.The effects of tool materials,cutting parameters and cutting methods on the tool wear patterns are investigated.Tool wear process is traced using three-dimension microscope,SEM and EDS;the tool wear mechanisms are revealed through a combined analysis of the cutting and friction experiments.(3)The machined surface formation process during cutting PRTMCs is investigated by analyzing the removal behavior of the reinforcement.Besides,the key factors affecting surface defect formation are confirmed,and the effects of cutting conditions,e.g.tool type and cutting parameters on the machined surface roughness and subsurface metallographic microstructure are evaluated.(4)Based on the above results,a parametric study on cutting forces,cutting temperature and machined surface integrity is performed for optimizing the milling parameters of PRTMCs.At last,a processing program for machining an aircraft component with rudder surfaces is proposed and an experimental verification is accordingly conducted.