EFFECT OF DOUBLE THERMAL PRE-AGEING ISOTHERMAL TREATMENT ON VICKER’S MICRO-HARDNESS OF Ti6Al4V ALLOYS FOR DENTAL IMPLANT APPLICATIONS

Abstract

Ti alloys have found wide range of engineering applications in different sectors due to excellent

properties they possess. Ti6Al4V is a class of Titanium alloys that has been referred to as a bio

alloy due to its biocompatibility, good osteointegration with no adverse tissue reaction.

Microhardness measurements have been used in non-destructive testing for qualitative analysis

and as a predictive tool in most processing conditions involving Ti6Al4V alloys. Vickers'

microhardness (Hv) test was conducted on double thermal treated samples and untreated samples

to investigate the effect of pre-ageing temperature and ageing time on the hardness of Ti6Al4V

alloy. A quick screening method for selecting some of the most effective factors for further

experimental design based on design of experiment (DOE) was presented. The model uses two

level factorial design of 16 runs to evaluate the effect of four factors namely - A: Pre-ageing time,

B: Pre-ageing temperature, C: Ageing time and D: Ageing temperature on Vickers' microhardness

response. The two-level factorial design was selected for the model because it could model

interaction effects. The Hv of the untreated specimen was 372.67, however, there was significant

improvement in the microhardness values of double thermal treatment samples. The

microhardness at pre-ageing temperature of 300oC and soaking time of 2 Hours was 779, while

at 8 Hours the value was 831.67Hv; this corresponds to an increase in Hv of 6.76%. The

interaction of BC, BD and CD were found to be significant, while optimization of the process

parameters was achieved at a ‘Desirability’ of 0.971.