Nanostructured Ti6Al4V alloy was successfully formed through mechanical alloying of a stoichiometric 
mixture of Ti, Al and V powders. Phase evolutions of the milled powders were investigated by XRD. The 
Ti(Al,V) solid solution formed after 10 h milling. Prolongation of the milling process up to 20 h lead to a 
structure consisting of the B-Ti phase in the a-Ti(Al) matrix. The nanostructured Ti6Al4V alloy had a grain 
size and hardness of 20 nm and 600 Hv respectively. Thermal stability of the alloyed powder was good as 
it's hardness increased to 950 Hv after 5 hr heat treatment at 1100 degrees Celsius.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3488

Abbasi, M.H.

Enayati, M.H.

Karimzadeh, F.

Salehikahrizsangi, P.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 1, 01PCN20 (3pp) (2012) 
 
 
2304-1862/2012/1(1)01PCN20(3) 01PCN20-1  2012 Sumy State University 
Development and Characterization of Nanostructured Ti6Al4V Alloy 
 
F. Karimzadeh*, P. Salehikahrizsangi, M.H. Enayati, M.H. Abbasi 
 
Department of Materials Engineering, Isfahan University of Technology, Isfahan 81736-55953, Iran 
 
 (Received 18 June 2012; published online 23 August 2012) 
 
Nanostructured Ti6Al4V alloy was successfully formed through mechanical alloying of a stoichiometric 
mixture of Ti, Al and V powders. Phase evolutions of the milled powders were investigated by XRD. The 
Ti(Al,V) solid solution formed after 10 h milling. Prolongation of the milling process up to 20 h lead to a 
structure consisting of the -Ti phase in the -Ti(Al) matrix. The nanostructured Ti6Al4V alloy had a grain 
size and hardness of 20 nm and 600 Hv respectively. Thermal stability of the alloyed powder was good as 
it's hardness increased to 950 Hv after 5 hr heat treatment at 1100 C.  
 
Keywords: Hardness, Heat Treatment, Nanostructure, Solid Solution, Ti6Al4V Alloy. 
 
 PACS numbers: 61.05.cp, 62.20.Qp 
 
 
                                                          
* karimzadeh_f@cc.iut.ac.ir 
1. INTRODUCTION 
 
Titanium alloys primarily stand out due to two 
major properties: high specific strength and excellent 
corrosion resistance. This also explains their 
preferential use in the aerospace, the chemical industry 
and medical engineering sector [1]. Usually titanium 
alloys are classified as ,    and  alloys. The    
alloys are the most widely used alloy group [1]. Among 
the    alloys, Ti-6Al-4V is by far the most popular 
titanium alloy. The aerospace industry is the largest 
user of Ti-6Al-4V alloy due to the good balance of its 
properties [1]. Despite all the mentioned advantages, 
the Ti6Al4V alloy still suffers from poor tribological 
properties, poor oxidation behavior and low hardness.  
The properties of titanium alloys are essentially 
determined by two factors: the chemical composition 
and the microstructure [1-3]. The type of phases 
present, grain size and grain shape, morphology and 
distribution of the fine microstructure determine the 
properties and therefore the application of titanium 
alloys [3]. Reig et al. [4] analysed the effect of Ti6Al4V 
microsphere size on the mechanical properties of 
porous Ti6Al4V specimens developed by sintering. 
Based on this research, optimum mechanical properties 
were obtained when sintering the smallest size 
microspheres. Titanium alloys with smaller grain size 
unexpectedly exhibit more stable thermal behaviour 
upon heating [5]. According to Mahboubi et al. [6], 
higher microhardness was obtained for the as-milled 
nanostructured Ti6Al4V powder in comparison to the 
raw Ti6Al4V alloy. Thus, production of nanostructured 
titanium alloys could possibly benefit by yielding 
improved thermal stability at high working 
temperatures, good erosion behavior, good wear 
resistance and good fracture toughness.  
Casting routes for the production of titanium and 
its alloys, with high levels of vulnerability to oxidation, 
have always been much troublesome [1]. Solid state 
synthesis of titanium alloys is thus of practical 
importance. Mechanical milling (MM) is a cost effective 
solid state route for the production of nanosized 
powders [7, 8]. 
In the present study solid state synthesis of 
nanostructured Ti6Al4V alloy during mechanical 
alloying of elemental powders and the formation 
mechanism were investigated.  
 
2. EXPERIMENTAL PROCEDURE 
 
Ball milling of titanium, aluminium and vanadium 
elemental powders was conducted under protective 
atmosphere of Ar (99.999 % pure) using a planetary 
(Retsch PM200 type) ball milling machine. The 
grinding media is made of stainless steel. Milling 
parameters are given in Table 1. 
 
Table 1 – The milling parameters used for the process. 
 
Rotation speed of vial(rpm) 500 
Vial material Hardened Cr steel 
Vial capacity(ml) 120 
Ball material Hardened C steel 
Diameter of balls(mm) 20 
Number of balls 5 
Ball to powder weight ratio 10:1 
Total powder mass(g) 17 
 
Sampling was done from milled materials at 
selected time intervals to study the phase evolution  
using Philips Xpert MPD x-ray diffraction (XRD) 
machine fitted with Cu kα radiation (   1.54 Å), and 
0.02 step size scanned from 20 to 90° (2 ). Changes of 
the grain size and strain of the samples were revealed 
by use of the Williamson-Hall formula (Equation 1) 
[9, 10]: 
 
 cos   0.9 /D + sin  (1) 
 
where  is the diffraction peak width at half maximum 
intensity, λ the wave length of the radiation used (1.54 
Å), D the grain size,  the Bragg diffraction angle and ε 
is the internal lattice strain. This strain can be 
estimated from the linear slope of cos  versus sin , 
and the grain size can be estimated from the intersect 
of this line at sin   0. 
 
 
 F. KARIMZADEH, P. SALEHIKAHRIZSANGI PROC. NAP 1, 01PCN20 (2012) 
 
 
01PCN20-2 
3. RESULT AND DISCUSSION 
 
X-ray diffraction patterns of Ti-6wt %Al-4wt %V 
powder milled for 0, 5, 10, 15 and 20 hr are shown in 
Fig. 1.  
 
 
 
Fig. 1 – XRD patterns of Ti-6wt%Al-4wt%V powder at 
different milling times 
 
By increasing the milling time, the continuous 
decrease in the intensities of diffraction peaks occurred. 
After 10 hr, the diffraction peaks of both Al and V 
disappeared in XRD pattern. These could be due to 
gradual diffusion of Al and V atoms in to the Ti atomic 
structure, since Al and V have enough solid state 
solubility in Ti in contrast to zero solubility of Ti in Al 
and V [11, 12]. Previous investigations have also called 
for Al atoms' diffusion in Ti lattice structure as the 
cause for Al diffraction peaks’ disappearance after 4 hr 
of ball milling [13]. Trends of Ti peak shift are 
especially depicted for Ti(101) peak before and after 10 
hr of milling (Fig. 2). This shift must be caused by 
solution of one element in Ti. Before 10 hr, the shift in 
Ti peaks towards lower angles occurs due to the 
diffusion of Al (rAl  1.82 Å) and V (rV  1.92 Å) atoms 
in to Ti (rTi  2 Å) interstitial spaces, and a metastable 
Ti(Al,V) solid solution is formed in this way (Fig. 2.a). 
Beyond 10 h, the Ti(Al,V) diffraction peaks shift to 
higher angles due to increase of V content in Ti(Al,V) as 
well as simoltaneous  homogenous distribution of V 
atoms in the solid solution structure (Fig. 2.b). By the 
end of this shift, -Ti(002) and -Ti(103) diffraction 
peaks are replaced with -Ti(110) and -Ti(211) peaks, 
subsequently and the stabilization of -Ti phase in the 
primary α-Ti matrix is thus guaranteed. The lattice 
parameter of the new -Ti phase is identical to the 
literature values and corresponds to the bcc structure 
with a  3.23 Å. Peak broadening can be indicative of 
small crystallite size and increased lattice strains [14]. 
However, stress gradients and/or chemical 
heterogeneities can also cause peak broadening [14]. 
In order to assure the effect of Al and V atoms' 
dissolution on Ti peak shift, pure Titanium's (101) peak 
position at different milling times was also investigated 
and no shift occurred (Fig. 3). No Fe contamination was 
detected after EDAX analysis. Solid state solubility of 
Al and V in Ti could thus be the only cause for the shift 
of Ti peaks in this research. Thus, after 20 hr milling, 
the solid state in-situ synthesis of nanostructured 
Ti6Al4V alloy with grain size and lattice strain of about 
20 nm and 0.08 % respectively was obtained. 
 
 
 
Fig. 2 – Ti(101) peak shift towards: a. lower angles for milling 
times less than 10 hr, b. higher angles for milling times more 
than 10 hr 
 
 
 
Fig. 3 – stable position of pure Ti(101) peak before and after 
10 h of ball milling 
 
The nanostructured alloy had a hardness of 
600 Hv which increased to 950 Hv through 5 hr 
heat treatment at 1100 C. During the quench from 
solution temperature, both the decomposition of the 
transformed  phase or the precipitation of aluminium 
rich 2 in the primary alpha phase could cause such an 
increase in hardness [15]. Thus, the nanostructured 
Ti6Al4V alloy has good thermal stability as well as 
high hardness. Continuation of milling for 110 hr 
yielded an amorphous structure (Fig. 4).  
 
  
 
Fig. 4 – The Ti-6wt %Al-4wt %V powder diffraction patterns 
obtained through different milling times after the Ti6Al4V 
alloy formation 
 
After 110 hr milling, the stable position of the peak 
of the amorphous phase indicates that no secondary 
amorphous phase has been formed (Fig. 5). 
 
 DEVELOPMENT AND CHARACTERIZATION OF NANOSTRUCTURED… PROC. NAP 1, 01PCN20 (2012) 
 
 
01PCN20-3 
 
 
Fig. 5 – Stable peak position of the amorphous phase after 
110 hr milling 
4. CONCLUSION 
 
The nanostructured Ti6Al4V alloy with grain size of 
about 20 nm was  successfully produced through 20 h of 
mechanical alloying of elemental powders. The alloy's 
response to 5 hr heat treatment at 1100 ˚C was an in-
crease in hardness from 600 Hv to  950 Hv. This 
good thermal stability of the alloy could be assigned to 
decomposition of the  phase or precipitation of the 
aluminium rich 2 phase in the primary  matrix. 
 
 
 
 
REFERENCES 
 
1. C. Leyens, M. Peters, Titanium and Titanium Alloys 
(Koln: Wiley-VCH Publishing: 2003). 
2. S. Malinov, W. Sha, Z. Guo, C.C. Tang, A.E. Long, Mater. 
Character. 48, 279 (2002). 
3. A. Mahboubi, F. Karimzadeh, M.H.Enayati, Mater. Design 
31, 3954 (2010). 
4. L. Reig, V. Amigo, D.J. Busquets, J.A. Calero, J. Mater. 
Proces. Tech. 212, 3 (2011). 
5. G.J. Fan, W.N. Gao, M.X. Quan, Z.Q. Hu, Mater. Lett. 23, 
33 (1995). 
6. A. Mahboubi, M.H. Enayati, F. Karimzadeh, Adv. Powder 
Tech. 21, 336 (2010). 
7. M.J. Bermingham, Mater. Forum 31, 84 (2007). 
8. C. Suryanarayana, Adv. Mater. Sci. 18, 203 (2008). 
9. B.D. Callity, Elements of X-ray Diffraction (Addison-
Wesley Publishing: 1978). 
10. C. Suryanarayana, X-ray Diffraction: A Practical Ap-
proach (1988). 
11. C. Suryanarayana, Mater. Sci. Eng. A 158, 93 (1992). 
12. P. Pietrokowsky, J. Metals, 627 (1952). 
13. J. Morales Hernandez, J. Alloys Compd. 388, 266 (2005). 
14. T. Ungar, 114 (2006). 
15. P.J. Fopiano, C.F. Hickey, Army Materials and Mechanics 
Research Center, 1968. 
 
 


Development and Characterization of Nanostructured Ti6Al4V Alloy

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 1, 01PCN20 (3pp) (2012)   2304-1862/2012/1(1)01PCN20(3) 01PCN20-1  2012 Sumy State University Development and Characterization of Nanostructured Ti6Al4V Alloy  F. Karimzadeh*, P. Salehikahrizsangi, M.H. Enayati, M.H. Abbasi  Department of Materials Engineering, Isfahan University of Technology, Isfahan 81736-55953, Iran   (Received 18 June 2012; published online 23 August 2012)  Nanostructured Ti6Al4V alloy was successfully formed through mechanical alloying of a stoichiometric mixture of Ti, Al and V powders. Phase evolutions of the milled powders were investigated by XRD. The Ti(Al,V) solid solution formed after 10 h milling. Prolongation of the milling process up to 20 h lead to a structure consisting of the -Ti phase in the -Ti(Al) matrix. The nanostructured Ti6Al4V alloy had a grain size and hardness of 20 nm and 600 Hv respectively. Thermal stability of the alloyed powder was good as it's hardness increased to 950 Hv after 5 hr heat treatment at 1100 C.   Keywords: Hardness, Heat Treatment, Nanostructure, Solid Solution, Ti6Al4V Alloy.   PACS numbers: 61.05.cp, 62.20.Qp                                                             * karimzadeh_f@cc.iut.ac.ir 1. INTRODUCTION  Titanium alloys primarily stand out due to two major properties: high specific strength and excellent corrosion resistance. This also explains their preferential use in the aerospace, the chemical industry and medical engineering sector [1]. Usually titanium alloys are classified as ,    and  alloys. The    alloys are the most widely used alloy group [1]. Among the    alloys, Ti-6Al-4V is by far the most popular titanium alloy. The aerospace industry is the largest user of Ti-6Al-4V alloy due to the good balance of its properties [1]. Despite all the mentioned advantages, the Ti6Al4V alloy still suffers from poor tribological properties, poor oxidation behavior and low hardness.  The properties of titanium alloys are essentially determined by two factors: the chemical composition and the microstructure [1-3]. The type of phases present, grain size and grain shape, morphology and distribution of the fine microstructure determine the properties and therefore the application of titanium alloys [3]. Reig et al. [4] analysed the effect of Ti6Al4V microsphere size on the mechanical properties of porous Ti6Al4V specimens developed by sintering. Based on this research, optimum mechanical properties were obtained when sintering the smallest size microspheres. Titanium alloys with smaller grain size unexpectedly exhibit more stable thermal behaviour upon heating [5]. According to Mahboubi et al. [6], higher microhardness was obtained for the as-milled nanostructured Ti6Al4V powder in comparison to the raw Ti6Al4V alloy. Thus, production of nanostructured titanium alloys could possibly benefit by yielding improved thermal stability at high working temperatures, good erosion behavior, good wear resistance and good fracture toughness.  Casting routes for the production of titanium and its alloys, with high levels of vulnerability to oxidation, have always been much troublesome [1]. Solid state synthesis of titanium alloys is thus of practical importance. Mechanical milling (MM) is a cost effective solid state route for the production of nanosized powders [7, 8]. In the present study solid state synthesis of nanostructured Ti6Al4V alloy during mechanical alloying of elemental powders and the formation mechanism were investigated.   2. EXPERIMENTAL PROCEDURE  Ball milling of titanium, aluminium and vanadium elemental powders was conducted under protective atmosphere of Ar (99.999 % pure) using a planetary (Retsch PM200 type) ball milling machine. The grinding media is made of stainless steel. Milling parameters are given in Table 1.  Table 1 – The milling parameters used for the process.  Rotation speed of vial(rpm) 500 Vial material Hardened Cr steel Vial capacity(ml) 120 Ball material Hardened C steel Diameter of balls(mm) 20 Number of balls 5 Ball to powder weight ratio 10:1 Total powder mass(g) 17  Sampling was done from milled materials at selected time intervals to study the phase evolution  using Philips Xpert MPD x-ray diffraction (XRD) machine fitted with Cu kα radiation (   1.54 Å), and 0.02 step size scanned from 20 to 90° (2 ). Changes of the grain size and strain of the samples were revealed by use of the Williamson-Hall formula (Equation 1) [9, 10]:   cos   0.9 /D + sin  (1)  where  is the diffraction peak width at half maximum intensity, λ the wave length of the radiation used (1.54 Å), D the grain size,  the Bragg diffraction angle and ε is the internal lattice strain. This strain can be estimated from the linear slope of cos  versus sin , and the grain size can be estimated from the intersect of this line at sin   0.    F. KARIMZADEH, P. SALEHIKAHRIZSANGI PROC. NAP 1, 01PCN20 (2012)   01PCN20-2 3. RESULT AND DISCUSSION  X-ray diffraction patterns of Ti-6wt %Al-4wt %V powder milled for 0, 5, 10, 15 and 20 hr are shown in Fig. 1.     Fig. 1 – XRD patterns of Ti-6wt%Al-4wt%V powder at different milling times  By increasing the milling time, the continuous decrease in the intensities of diffraction peaks occurred. After 10 hr, the diffraction peaks of both Al and V disappeared in XRD pattern. These could be due to gradual diffusion of Al and V atoms in to the Ti atomic structure, since Al and V have enough solid state solubility in Ti in contrast to zero solubility of Ti in Al and V [11, 12]. Previous investigations have also called for Al atoms' diffusion in Ti lattice structure as the cause for Al diffraction peaks’ disappearance after 4 hr of ball milling [13]. Trends of Ti peak shift are especially depicted for Ti(101) peak before and after 10 hr of milling (Fig. 2). This shift must be caused by solution of one element in Ti. Before 10 hr, the shift in Ti peaks towards lower angles occurs due to the diffusion of Al (rAl  1.82 Å) and V (rV  1.92 Å) atoms in to Ti (rTi  2 Å) interstitial spaces, and a metastable Ti(Al,V) solid solution is formed in this way (Fig. 2.a). Beyond 10 h, the Ti(Al,V) diffraction peaks shift to higher angles due to increase of V content in Ti(Al,V) as well as simoltaneous  homogenous distribution of V atoms in the solid solution structure (Fig. 2.b). By the end of this shift, -Ti(002) and -Ti(103) diffraction peaks are replaced with -Ti(110) and -Ti(211) peaks, subsequently and the stabilization of -Ti phase in the primary α-Ti matrix is thus guaranteed. The lattice parameter of the new -Ti phase is identical to the literature values and corresponds to the bcc structure with a  3.23 Å. Peak broadening can be indicative of small crystallite size and increased lattice strains [14]. However, stress gradients and/or chemical heterogeneities can also cause peak broadening [14]. In order to assure the effect of Al and V atoms' dissolution on Ti peak shift, pure Titanium's (101) peak position at different milling times was also investigated and no shift occurred (Fig. 3). No Fe contamination was detected after EDAX analysis. Solid state solubility of Al and V in Ti could thus be the only cause for the shift of Ti peaks in this research. Thus, after 20 hr milling, the solid state in-situ synthesis of nanostructured Ti6Al4V alloy with grain size and lattice strain of about 20 nm and 0.08 % respectively was obtained.    Fig. 2 – Ti(101) peak shift towards: a. lower angles for milling times less than 10 hr, b. higher angles for milling times more than 10 hr    Fig. 3 – stable position of pure Ti(101) peak before and after 10 h of ball milling  The nanostructured alloy had a hardness of 600 Hv which increased to 950 Hv through 5 hr heat treatment at 1100 C. During the quench from solution temperature, both the decomposition of the transformed  phase or the precipitation of aluminium rich 2 in the primary alpha phase could cause such an increase in hardness [15]. Thus, the nanostructured Ti6Al4V alloy has good thermal stability as well as high hardness. Continuation of milling for 110 hr yielded an amorphous structure (Fig. 4).      Fig. 4 – The Ti-6wt %Al-4wt %V powder diffraction patterns obtained through different milling times after the Ti6Al4V alloy formation  After 110 hr milling, the stable position of the peak of the amorphous phase indicates that no secondary amorphous phase has been formed (Fig. 5).   DEVELOPMENT AND CHARACTERIZATION OF NANOSTRUCTURED… PROC. NAP 1, 01PCN20 (2012)   01PCN20-3   Fig. 5 – Stable peak position of the amorphous phase after 110 hr milling 4. CONCLUSION  The nanostructured Ti6Al4V alloy with grain size of about 20 nm was  successfully produced through 20 h of mechanical alloying of elemental powders. The alloy's response to 5 hr heat treatment at 1100 ˚C was an in-crease in hardness from 600 Hv to  950 Hv. This good thermal stability of the alloy could be assigned to decomposition of the  phase or precipitation of the aluminium rich 2 phase in the primary  matrix.     REFERENCES  1. C. Leyens, M. Peters, Titanium and Titanium Alloys (Koln: Wiley-VCH Publishing: 2003). 2. S. Malinov, W. Sha, Z. Guo, C.C. Tang, A.E. Long, Mater. Character. 48, 279 (2002). 3. A. Mahboubi, F. Karimzadeh, M.H.Enayati, Mater. Design 31, 3954 (2010). 4. L. Reig, V. Amigo, D.J. Busquets, J.A. Calero, J. Mater. Proces. Tech. 212, 3 (2011). 5. G.J. Fan, W.N. Gao, M.X. Quan, Z.Q. Hu, Mater. Lett. 23, 33 (1995). 6. A. Mahboubi, M.H. Enayati, F. Karimzadeh, Adv. Powder Tech. 21, 336 (2010). 7. M.J. Bermingham, Mater. Forum 31, 84 (2007). 8. C. Suryanarayana, Adv. Mater. Sci. 18, 203 (2008). 9. B.D. Callity, Elements of X-ray Diffraction (Addison-Wesley Publishing: 1978). 10. C. Suryanarayana, X-ray Diffraction: A Practical Ap-proach (1988). 11. C. Suryanarayana, Mater. Sci. Eng. A 158, 93 (1992). 12. P. Pietrokowsky, J. Metals, 627 (1952). 13. J. Morales Hernandez, J. Alloys Compd. 388, 266 (2005). 14. T. Ungar, 114 (2006). 15. P.J. Fopiano, C.F. Hickey, Army Materials and Mechanics Research Center, 1968.   

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Development and Characterization of Nanostructured Ti6Al4V Alloy

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