Experimental Research On Indentation Response Of TC4 Titanium Alloy

As a lightweight structural material,TC4 titanium alloy is widely used in the manufacture of aircraft engines and aircraft body structural parts due to its high specific strength,corrosion resistance,heat resistance and other comprehensive properties and high structural benefits.The mechanical properties such as hardness and elastic modulus of TC4 material are the key to ensure its safe and stable service.However,most of the research on the mechanical properties of TC4 material is still at the macro level at home and abroad,and the service conditions of TC4 materials are two types of working conditions: normal temperature and high temperature below 400?.Therefore,it is urgent and necessary to carry out micro-nano indentation tests on TC4 titanium alloy materials at room temperature and high temperature to study the changes in its mechanical properties.This article comprehensively analyzes the domestic and foreign research status of micro-nano indentation testing technology and TC4 titanium alloy materials.Based on the actual service conditions of TC4 materials,a follow-up test plan is proposed: This article performs micro-nano indentation tests on TC4 materials at room temperature and high temperature.By comparing the load-displacement(p-h)curve and the residual indentation morphology under different conditions,the difference between the mechanical properties of TC4 materials under high load and micro-zone and small load is mainly compared at room temperature.The effect of temperature on the mechanical properties of TC4 materials is mainly investigated at high temperatures.Before the start of the indentation test,the basic principles of the micronano indentation test technology,the selection of the indenter material,and the geometrical dislocation theory model corresponding to the indentation size effect were introduced in detail,which provides a theoretical basis for subsequent indentation tests.The standard indentation block is used to calibrate the indentation curve of the micro-nano indenter independently developed by the laboratory to ensure the test accuracy of the instrument.The indenter was used to test the TC4 material under large load at room temperature.By analyzing the load-indentation displacement curve and using scanning electron microscope to observe the appearance of the residual indentation,a macro of the mechanical properties of the TC4 material was obtained.Anton Paar commercial indenter(with micro-monitoring function)was used to perform small load indentation test in two-phase micro-region for TC4 samples after metallographic corrosion,and the mechanical properties of different phase regions were compared and analyzed.It is concluded that at the macro level,due to the size effect,the hardness and elastic modulus decrease with the increase of the maximum indentation load,and in the range of 4 ~ 8N The internal decline is obvious,and it tends to be stable in the range of 8 ~ 14 N.At the micro level,the mechanical properties such as hardness and elastic modulus of the ? phase and ?-? mixed phase are significantly different.The hardness and elastic modulus of the ? phase are both high.Based on the hardness and elastic modulus values of ?-? mixed phase;comparing and analyzing the indentation test results of large load and small load of micro-region,it is found that the macro mechanical properties of TC4 mainly depend on the mechanical properties of ? phase.This article uses a laboratory-developed high-temperature micro-nano indenter to carry out high-temperature indentation test research on TC4 materials.High temperature indentation tests were performed at four temperature gradients of room temperature,200 ° C,300 ° C,and 400 ° C,with the loading of 8N,10 N,12Nand 14 N.By analyzing the measured p-h curve,the change law of hardness and elastic modulus with temperature,and using field emission scanning electron microscope for auxiliary observation,it was found that the hardness and elastic modulus of TC4 materials showed a gradual decline with increasing temperature,and the decline trend gradually flattened.