Prediction of Compressive Strength of Biodegradable Mg-Zn/HA Composite via Response Surface Methodology and Its Biodegradation

doi:10.1007/s40195-016-0410-5

Abstract

Abstract:

：This work aimed to fabricate magnesium zinc/hydroxyapatite (Mg-Zn/HA) composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed (200-300 r/min), ball-to-powder weight ratio (5-12.5) and HA content (2.6-10 wt%) on the compressive strength of Mg-Zn/HA composite was investigated. The model shows that high compressive strength of Mg-Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-to-powder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg-Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg-Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg-Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties.

Key words: Powder metallurgy, Magnesium-zinc alloy, Hydroxyapatite, Response surface methodology, Biodegradation

Loy Liang Soon, Hussain Zuhailawati, Ismail Suhaina, Brij Kumar Dhindaw. Prediction of Compressive Strength of Biodegradable Mg-Zn/HA Composite via Response Surface Methodology and Its Biodegradation[J]. Acta Metallurgica Sinica (English Letters), 2016, 29(5): 464-474.

Figures/Tables 16

Table 1 Process parameters in CCD, coded and uncoded values

Level	Milling speed (r/min)	BPR	HA content (wt%)
-α	165.91	2.44	0.08
-1	200	5	2.6
0	250	8.75	6.3
1	300	12.5	10
+α	334.09	15.06	12.52

Table 2 Experimental design matrix

Run order	Milling speed	BPR	HA content
1	+	-	+
2	-	-	+
3	+	-	-
4	0	0	0
5	0	-α	0
6	-	+	-
7	-	+	+
8	0	0	-α
9	0	+α	0
10	0	0	0
11	0	0	0
12	-	-	-
13	0	0	0
14	0	0	0
15	-α	0	0
16	0	0	+α
17	+	+	-
18	0	0	0
19	+	+	+
20	+α	0	0

Table 3 Compressive strength results

Run order	Milling speed	BPR	HA content	Compressive strength (MPa)
1	?	-	+	198.72
2	-	-	+	153.08
3	?	-	-	244.16
4	0	0	0	230.08
5	0	-α	0	168.13
6	-	+	-	173.73
7	-	+	+	176.45
8	0	0	-α	238.11
9	0	-α	0	239.26
10	0	0	0	191.77
11	0	0	0	202.47
12	-	-	-	163.02
13	0	0	0	216.24
14	0	0	0	175.92
15	-α	0	0	118.23
16	0	0	+α	115.71
17	+	+	-	178.53
18	0	0	0	146.73
19	+	+	+	173.96
20	+α	0	0	175.04

Table 4 Regression analysis results for the mathematical model and coefficient of model terms for the formulation of Mg-Zn/HA composites

Source	Sum of squares	DF	Mean square	F value	p value
Regression	12,392.60	4	3098.2	3.45	0.034
Linear	9055.9	3	3018.6	3.37	0.047
Milling speed	3694.4	1	3694.4	4.12	0.061
BPR	293.6	1	293.6	0.33	0.576
HA content	5067.9	1	5067.9	5.65	0.031
Square of milling speed	3336.7	1	3336.7	3.72	0.073
Lack of fit	9019.5	10	901.9	1.02	0.527

Table 5 Parameters, relative density, strain level, crystallite size and compressive strength for selected samples

Run order	Milling speed (r/min)	BPR	HA content (wt%)	Relative density (%)	Strain level	Crystallite size (A° )	Compressive strength (MPa)
1	300.00	5	10	93.07	0.058	564.5	199
2	200	5	10	94.42	0.051	635.5	153
3	300	5	2.6	95.12	0.041	801	244
17	300	12.5	2.6	93.58	0.066	495.4	179

Fig. 1 Optical micrographs of the samples: a sample 1 (300 r/min, BPR 5, 10 wt% HA); b sample 2 (200 r/min, BPR 5, 10 wt% HA); c sample 3 (300 r/min, BPR 5, 2.6 wt% HA); d sample 17 (300 r/min, BPR 12.5, 2.6 wt% HA)

Fig. 2 SEM images of sample 1 a, sample 2 b and sample 3 c

Fig. 3 SEM images and EDX plots at two different spots of sample 1 for primary phase a and secondary phase b

Fig. 4 Contour plot for interaction between HA content and milling speed

Fig. 5 Contour plot for interaction between BPR and milling speed

Fig. 6 Contour plot for interaction between HA content and BPR

Fig. 7 XRD patterns for Mg-Zn/HA composites with 2.6, 10 and 30 wt% HA: a normal pattern; b logarithmic scaled the pattern to increase the visibility of the HA peaks

Fig. 8 Weight gain of the Mg-Zn/HA composites with different HA contents

Fig. 9 Surface morphology after immersion in SBF for 5 h of the samples without HA a and with 1 wt% b, 5 wt% c, 8 wt% d and 11 wt% e HA

Fig. 10 EDX analysis of passivation layer on the samples with different HA contents: a 0 wt%; b 1 wt%; c 5 wt%; d 8 wt%; e 11 wt%

References 15

[1]	S. Zhang, X. Zhang, C. Zhao, J. Li, Y. Song, C. Xie, H. Tao, Y.Zhang, Y. He, Y. Jiang, Acta Biomater. 6, 626(2010)
[2]	E.M. Salleh, H. Zuhailawati, S. Ramakrishnan, M. Gepreel, J.Alloys Compd. 644, 476(2015)
[3]	E. Zhang, D. Yin, L. Xu, L. Yang, K. Yang, Mater. Sci. Eng. C 29, 987 (2009)
[4]	K. Khalil, E. Sherif, A. Almajid, Int. J. Electrochem. Sci. 6,6184(2011)
[5]	D. Liu, M. Chen, X. Ye, Front. Mater. Sci. China 4, 139 (2010)
[6]	Y. Zhao, J. Si, J. Song, X. Hui, Mater. Lett. 118, 55(2014)
[7]	M. Datta, D. Chou, D. Hong, P. Saha, S. Chung, B. Lee, A.Sirinterlikci, M. Ramanathan, A. Roy, P. Kumta, Mater. Sci.Eng. B 176, 1637 (2011)
[8]	Q. Chang, H. Ru, D. Chen, X. Yue, L. Yu, C. Zhang, J. Mater.Sci. Technol. 27, 546(2011)
[9]	W. Cao,
[10]	K. Khalil, Int. J. Electrochem. Sci. 7, 10698(2012)
[11]	M. Hasniyati, H. Zuhailawati, S. Ramakrishnan, B. Dhindaw, S.Noor, Surf. Eng. 17, 432(2015)
[12]	F. Shehata, A. Fathy, M. Abdelhameed, S. Moustafa, Mater.Des. 30, 2756(2009)
[13]	H. Liebowitz, Fracture of Nonmetals and Composites (Academic Press, New York, 1972), pp. 780-782
[14]	J. Howard, F. Allen, G. Shields,Netherlands, 1999)
[15]	Z. Yang, J. Li, J. Zhang, G. Lorimer, J. Robson, Acta Metall.Sin.(Engl. Lett.) 21, 313(2008)