INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,  
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)  
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue XII, December 2025  
Heat Transfer Coefficient Experimental Modelling of Aluminium  
6061 Shape Casting in Green-Sand Mould  
1Musbau Godfrey, 3 Suleiman, Lawal T.I., 2Samaila Umaru, 1Mohammed Habib Muhammad, 1Yahaya  
Ibrahim., 1Kazeem Lamid, 1Samuel Kayode Makinde, and 1Ndubuisi Divine Utazi  
1 Department of Mechanical Engineering, Faculty of Air Engineering, Airforce Institute of Technology,  
Nigeria Airforce Base, Kaduna, Nigeria  
2 Professor, Department of Mechanical Engineering, Ahmadu Bello University, Zaria, Nigeria,  
3 Development and Production Unit, Nigeria Upstream Petroleum Regulatory Commission (NUPRC),  
Headquarters Utako, Abuja, Nigeria  
DOI : https://doi.org/10.51583/IJLTEMAS.2025.1412000096  
Received: 29 May 2025; Accepted: 03 June 2025; Published: 09 January 2026  
ABSTRACT  
This study investigates the casting of aluminum alloy 6061 using green sand molds to evaluate the heat transfer  
coefficient (HTC) and solidification behaviour for different cast shapes. The shapes employed for the study  
includes rectangular plate, square bar and cylindrical bar. Aluminum alloy 6061 ingots were melted and poured  
at 700°C into the moulds of rectangular plate, square bar, and cylindrical bar configurations. Experimental results  
revealed that the HTC varies across different shapes, with the rectangular plate exhibiting the highest average  
HTC of 131.6 W/m²K, followed by the cylindrical bar (98 W/m²K) and square bar (73.7 W/m²K). The study  
demonstrated that shapes with lower casting modulus exhibit faster solidification due to enhanced heat  
dissipation. The casting of shapes that involves using aluminium alloy 6061 solidified within 105 seconds after  
pouring of the molten metal into mould cavity and also plate was the first to solidify. The thermal conductivity  
of the alloy was consistent with ASTM standards, confirming the material's suitability for casting applications.  
The experimental result shows that thermal conductivity of the alloy was 102.3 WmK and the value was within  
range of stated value (85 - 173 W/mK) by ASTM. Heat transfer coefficient (HTC) in the cast objects was 101.1  
W/m2K. These findings highlight the influence of casting geometry on heat transfer and solidification  
characteristics, providing valuable insights for optimizing casting processes.  
Keywords: Aluminum alloy 6061, Heat transfer coefficient, Solidification time, Casting modulus, Green sand  
mold, Thermal conductivity, Casting geometry.  
INTRODUCTION  
The casting process is an essential manufacturing technique widely used in various industries, including  
automotive, aerospace, and industrial machinery. Shape casting is a process by which metal is transformed from  
ingot or scrap to a final form required by a designer (Jolly & Katgerman, 2022, Olofsson et al., 2020). The shape  
can be in plate and bar form all depends on design requirement and investigating interfacial heat transfer  
coefficient is necessary for minimising design requirement and cost. Aluminium 6061 alloy has gained  
significant attention due to its desirable properties, including light weight, high strength, and excellent corrosion  
resistance (Chikhale et al., 2016; Samuel et al., 2021). In casting Al 6061 in a green-sand mould, understanding  
the heat transfer characteristics is crucial for optimizing the casting process, improving product quality, and  
reducing energy consumption. Understanding heat transfer characteristics is crucial for optimizing the casting  
process of Al 6061 in green-sand moulds. The effective heat transfer coefficient at the mould/metal interface  
plays a significant role in this process (Aroge et al., 2021, Sun & Chao, 2009). Factors such as pouring  
temperature and the presence of inclusions affect the cooling rate and quality of the casting (Rendi et al., 2021).  
The interfacial heat transfer coefficient (IHTC) varies with time during solidification and is essential for accurate  
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simulation of the casting process (Gowsalya et al., 2019). Thermal resistance within the casting, at the metal-  
mould interface, and within the mould itself significantly impacts the heat transfer process (Shukla et al., 2020).  
Different mould materials, such as green sand and mullite, affect heat distribution during solidification (Shukla  
et al., 2020). Accurate modelling and simulation of these heat transfer characteristics, considering temperature-  
dependent properties of materials, can lead to improved casting quality and process optimization (Shukla et al.,  
2020; Sun & Chao, 2009). This research paper aims to investigate the heat transfer coefficient during the casting  
of Al 6061 in a green-sand mould and develop a predictive model for the process. The study will involve  
experimental analysis, data collection, and numerical modelling to provide a comprehensive understanding of  
the heat transfer mechanisms involved.  
Green sand casting is a complex process influenced by numerous factors affecting casting quality. Optimization  
of process parameters is crucial for efficient and economical production (Banchhor & Ganguly, 2014). The  
process involves pouring molten metal into a sand mould, where solidification occurs through nucleation and  
grain growth (Kumar et al., 2019). Mould variability plays a significant role in defect generation, with time-  
temperature behaviour of process parameters being essential for understanding and predicting defects (Pandit &  
Deshpande, 2023). Key parameters such as moisture content, green compressive strength, permeability, and  
mould hardness exhibit systematic, time-dependent behaviour. The metal/sand mould interface phenomena  
significantly impact the surface quality, microstructure, and mechanical properties of castings (Holtzer et al.,  
2015). To improve casting quality and reduce defects, it is necessary to move beyond traditional trial-and-error  
methods and employ statistical and artificial intelligence tools for process optimization (Banchhor & Ganguly,  
2014). The heat transfer coefficient (HTC) during the casting of Aluminium 6061, particularly in green-sand  
moulds, is critical for understanding the solidification process and optimizing casting quality. The study intends  
to encompass experimental approaches for modelling Aluminium 6061 Shape Casting in Green-Sand Mould  
Experimental Analysis  
An experimental investigation was conducted to determine the effective heat transfer coefficient at the metal-  
mould interface during the casting of Al 6061 in a green-sand mould. Experimental methods using  
thermocouples to measure temperature distributions in casting systems are commonly employed (Sun & Chao,  
2007; Sun et al., 2019). Inverse modelling techniques are utilized to calculate HTCs based on measured  
temperatures (Meneghini et al., 2007; Sun & Chao, 2007; Sun et al., 2019). HTCs vary depending on mould  
materials, with inorganic sand moulds exhibiting higher values (1000-1800 W·m−2·K−1) compared to organic  
sand moulds (300-700 W·m−2·K−1) (Sun et al., 2019). The lump capacitance method is proposed as an  
alternative approach for calculating HTCs in green sand mould casting (Sun & Chao, 2007). Factors influencing  
HTCs include metal head pressure (Meneghini et al., 2007), solidification phase changes, and mould moisture  
content (Sun & Chao, 2007). Numerical simulations using calculated HTCs show good agreement with  
experimental results, validating these methods for predicting temperature distributions and solidification times  
in casting processes (Sun & Chao, 2009; Sun et al., 2019).  
Experimental analysis has utilized diverse measurement techniques to evaluate the interfacial heat transfer  
coefficient (IHTC) during the solidification of aluminium alloys (Belsare et al., 2017). One widely applied  
method is the Inverse Control Volume Technique, which estimates heat flux and temperature at the mould  
surface by measuring temperatures at various points within the mould. This approach has been effectively  
employed for spherical aluminium alloy (Al 6061) castings, validating IHTC values against experimental data  
(Gowsalya et al., 2019). Another study adopted two different inverse methods—control volume and Beck’s  
approach—to estimate IHTC during the solidification of rectangular aluminium alloy castings. The findings  
demonstrated good agreement with existing literature, highlighting the reliability of these methodologies  
(Rajaraman et al., 2018).  
Modelling Approaches  
Mathematical modelling techniques have significantly advanced the simulation of solidification processes by  
incorporating critical parameters. For instance, the convective heat transfer coefficient has been effectively  
modelled in vertical twin roll casting processes, alongside factors like roll speed and melt superheat, to achieve  
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accurate predictions (Dhindaw et al., 2020). Similarly, studies on low-pressure die casting have demonstrated  
how interface pressure and water flow rates impact the interfacial heat transfer coefficient (IHTC), providing  
valuable insights for optimizing casting conditions (Zeng et al., 2019). Additionally, simulation tools such as  
COMSOL Multiphysics are widely utilized to model heat transfer and fluid dynamics in casting processes,  
enabling a comprehensive analysis of the interactions between various factors during solidification (Dhindaw et  
al., 2020).  
MATERIALS AND METHODS  
The primary material used in this study was aluminum alloy 6061, prepared in ingot form. The chemical  
composition of the alloy is shown in Table 1, and its physical and thermal specifications, as per ASTM standards,  
are detailed in Table 2. Additional materials included green sand for mold preparation and standard casting  
equipment, including a mold box, patterns, pliers, scissors, and a pouring cup. The electronic temperature  
recorder and thermocouples were used to measure temperature variations during the solidification process.  
Table 1: Composition of Aluminium 6061  
Aluminium 6061 Component  
Aluminium  
Magnesium  
Silicon  
Weight %  
96.20  
1.20  
0.75  
Iron  
0.70  
Copper  
0.40  
Zinc  
0.25  
Titanium  
0.15  
Manganese  
Chromium  
0.15  
0.20  
Table 2: Specification of Al6061 (ASTM)  
Specification  
Unit  
2400  
2700  
173  
85  
Liquid Density (kg/m3)  
Solid Density (kg/m3)  
Solid Thermal conductivity (W/mK)  
Liquid Thermal conductivity (W/mK)  
Fusion Temperature (oC)  
585  
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Solid Specific Heat (J/kgK)  
1050  
Liquid Specific Heat (J/kgK)  
Latent Heat of Fusion (J/kg)  
1090  
381900  
Experimental methods and Set Up  
Preparation of Mould and Patterns  
Three casting patterns were prepared to produce a rectangular plate, a square bar, and a cylindrical bar. The  
dimensions were as follows:  
1. Rectangular plate: 250 mm × 60 mm × 10 mm  
2. Square bar: 250 mm × 24.5 mm × 24.5 mm  
3. Cylindrical bar: 250 mm length, 27.6 mm diameter  
The patterns were used to create cavities in green sand molds. Molding and core-making were carried out to  
ensure dimensional accuracy and stability.  
Melting and Pouring  
Aluminum alloy ingots (10 kg) were melted in a gas furnace and heated to a pouring temperature of 700°C. The  
molten metal was poured into the pre-prepared mold cavities.  
Temperature Measurement  
Thermocouples connected to an electronic paperless recorder were used to monitor temperature variations at  
critical points within the molds and the castings.  
Four thermocouples were placed within the casting to measure the temperature gradient:  
푇 , 푇 , 푇푢푓, 푎푛푑 푇푢푐  
푖푓 푙푐  
Another thermocouple was positioned 50 mm from the mold wall to measure the sand mould temperature 푇 .  
푠
Figure 1 shows the positioning of thermocouple in cast plate. The blue pigment in Figure 1 was one-quarter of  
the plate pattern in which thermocouple mounted onto for measuring the readings of temperature points. The  
measuring points of temperature in the cast include 푇 , 푇 , 푇푢푓, 푎푛푑 푇푢푐 and these measured using  
푖푓 푙푐  
thermocouple through electronic paperless recorder.  
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Figure 1: Casting temperature measuring point Using Thermocouple Paperless Recorder  
The sand mould temperature (푇 ) measuring point was located 50 mm from the wooden or mould box. Four  
푠
points were used for positioning the thermocouple within the one quarter of the cast. The thermocouple used for  
measuring the temperature within the cast was positioned at 30mm (ℎ/2) from the edge of both width faces  
(60mm) of the cast in Figure 1. The thermocouple helps to measure temperature at four different points within  
cast. The thermocouple that measured sand mould temperature was positioned at centre point between pattern  
and core box within the mould.  
Determination of casting modulus  
The temperature per unit time or cooling of the casting depends on modulus of the casting and it is defined as  
ratio of volume to effective cooling surface area. The casting modulus, M, was calculated using (Bala and Khan,  
2013):  
푉
푚
푀 =  
(2.1)  
퐴
푚
Where Vm is the casting volume and Am is the effective cooling surface area.  
푡
푀푝 =  
푀푠 =  
(2.2)  
(2.3)  
2
푤
2
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Casting Shape  
Rectangular Plate  
Square Bar  
Modulus (M, mm)  
Solidification Time (ts, sec)  
4.0  
8.2  
320  
620  
720  
Cylindrical Bar  
10.0  
ꢀ
푀푐 =  
4
(2.4)  
Condition I (equation 2.1) holds if 퐿 > 5ꢁ  
Condition II (equation 2.2) holds if 퐿 > 5ꢂ  
Condition III (equation 2.3) holds if 퐿 > 5푑  
Determination of solidification time  
The solidification time (ꢁ푠) is the time required to complete solidification process in casting and depends on  
heat transfer across the casting surface and mould of the casting and given by Solidification time (ꢁ푠) was  
determined using the Stefanescu equation (Stefanescu, 2008):  
ꢁ푠 = 퐵(퐴푉  
)
(2.5)  
푚
ꢃ
푚
where, B is a constant incorporating material properties and n is the cooling rate exponent  
(푄 +푐 (ꢅ −ꢅ ))  
휌
푚
푉
푚
ꢆ
푚
ꢄ
푚
ꢁ푠 =  
(
)
(2.6)  
(
)
퐻ꢅ퐶  
ꢅ
푚
−ꢅ  
퐴
푚
푣
표
2
2
푐
푚
(ꢅ −ꢅ  
)
휌
ꢇ
휋
ꢆ
푚
푚
[
)] [  
] [  
1 + (  
]
퐵 =  
)
(2.7)  
(
ꢅ
푚
−ꢅ  
4푘휌푐  
ꢇ
표
RESULTS AND DISCUSSION  
Solidification Time Analysis  
The solidification times for the rectangular plate, square bar, and cylindrical bar castings were determined  
experimentally using thermocouple data. The results, presented in Table 3, indicate a direct relationship between  
casting modulus (M) and solidification time (ts) and the study boundary condition is in Table 3.  
Table 3: Solidification Time for Different Casting Shapes  
The cylindrical bar, having the highest modulus, exhibited the longest solidification time, while the rectangular  
plate solidified fastest. This outcome aligns with Chvorinov’s rule, which states that larger moduli correspond  
to longer solidification times due to slower heat dissipation.  
Table 4: Boundary condition of aluminium 6061  
Parameter  
Quantity  
Volume per workpiece  
0.00015m3  
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Length of Cast Alloy  
0.25m  
Pouring Temperature  
Time interval  
700 OC  
10 seconds  
The cooling of the casting depends on modulus of the casting (M) and it was calculated for different cast shapes  
based on same length (L) 125mm (Sun, et al., 2019).  
푡
10ꢈꢈ  
Plate modulus, 푀푝 =  
=
= 5ꢉꢉ  
2
2
(
)
퐿 > 5ꢁ = 5 10 = 50ꢉꢉ  
ꢋ
150,000  
ꢈ
ꢊꢈ  
=
=
= 30, 000 ꢉꢉ2  
푀
5
푤푖ꢀ푡ℎ  
24.5  
Square bar modulus, 푀푠 =  
=
= 6.1 ꢉꢉ  
4
4
(
)
퐿 > 5ꢂ = 5 24.5 = 122.5ꢉꢉ  
ꢋ
150,000  
ꢈ
ꢊꢈ  
=
=
= 24, 590 ꢉꢉ2  
푀
6.1  
ꢀ푖ꢌꢈ푒푡푒푟 (ꢀ)  
4
27.6  
Cylindrical bar, 푀푐 =  
=
= 6.9ꢉꢉ  
4
( )  
(
)
퐿 > 5 푑 = 5 27.6 = 138ꢉꢉ  
ꢋ
150,000  
ꢈ
ꢊꢈ  
=
=
= 21, 739 ꢉꢉ2  
푀
6.9  
The plate has lowest casting modulus of 5mm and this mean it has high cooling surface area of 30, 000 ꢉꢉ2 in  
comparing to other shapes used for the experiment. The heat transfer coefficient (HTC) of aluminium alloy was  
determined using experimental records of temperature distribution in the cast. Figure 2 shows the temperature  
gradient in plate cast and the pouring of molten metal was at 700oC.  
800  
700  
600  
Plate  
500  
400  
300  
200  
100  
0
Temp. oC  
Temp. oC  
Mould  
Temp. oC  
0
100  
200  
Time (s)  
Figure 2: Temperature profile of rectangular plate  
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Heat Transfer Coefficient (HTC) Analysis  
The heat transfer coefficient was calculated for each casting shape based on thermocouple readings. The  
rectangular plate exhibited the highest value, decreasing rapidly during solidification due to its higher surface  
area-to-volume ratio, which facilitated faster cooling. The cylindrical bar showed the lowest value throughout  
solidification, attributable to its smaller surface area relative to its volume, resulting in slower heat dissipation.  
This variation highlights the importance of HTC in determining the cooling rate and solidification behavior of  
castings. Table 4 presents heat transfer coefficient (HTC) of the alloy determined from the experimental result  
obtained for rectangular plate.  
o
The room/fluid temperature (푇 ) used for the study was at 25.3 C during the experiment. The length of cast  
푓
plate was 0.125m (half of the cast length) and heat energy was expected to transfer across the cast for  
solidification to complete. The expected HTC of the cast rectangular plate after 90 seconds was 48.4 W/m2K. It  
implies 48.4 W/m2K was the HTC of molten stage of the plate. The liquid thermal conductivity of the plate was  
at 111.8 W/mK. The ASTM-liquid thermal conductivity of the alloy in Table 3.2 was at 85 W/mK therefore  
efficiency of obtained HTC was at 68.5 % in plate.  
Table 5: HTC of Rectangular Plate  
T (oC)  
T-TS (oC)  
TS - Tf (oC)  
Time  
(s)  
TS  
HTC  
(W/m2K)  
(oC)  
10  
687.2  
674.3  
661.4  
648.6  
635.7  
622.9  
609.6  
596.3  
583.0  
569.7  
556.4  
543.0  
524.7  
506.4  
488.2  
680.7  
661.4  
642.1  
622.8  
603.5  
584.1  
564.8  
545.5  
526.2  
506.9  
487.6  
468.2  
444.0  
419.7  
395.5  
6.00  
12.9  
19.3  
25.8  
32.2  
38.8  
44.8  
50.8  
56.8  
62.8  
68.8  
74.8  
80.7  
86.7  
92.7  
655.4  
636.1  
616.8  
597.5  
578.2  
558.8  
539.5  
520.2  
500.9  
481.6  
462.3  
442.9  
418.7  
394.4  
370.2  
6.2  
20  
13.8  
30  
21.3  
40  
29.4  
50  
37.9  
60  
47.2  
70  
56.5  
80  
66.4  
90  
156.9  
180.9  
206.0  
233.7  
266.8  
304.2  
346.6  
100  
110  
120  
130  
140  
150  
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Table 5 presents summary of HTC in aluminium alloy cast and therefore it was observed that plate has high  
value of HTC in the casting with 131.6 W/m2K for the experiment. The HTC of cast square bar was at 73.6  
W/m2Kand HTC of cast cylindrical bar was at 98 W/m2K after 150 seconds  
800  
700  
600  
500  
Temp. oC  
400  
Square Temp. oC  
300  
200  
100  
0
Mould Temp. oC  
0
100  
200  
Time (s)  
Figure 3: Temperature-profile of square bar  
800  
700  
600  
500  
Cylindrical  
Temp. oC  
400  
300  
200  
100  
0
Temp. oC  
Mould Temp. oC  
0
100  
200  
Time (s)  
Figure 4: Temperature profile of cylindrical bar  
Rectangular plate solidified faster than other cast object due high HTC across its surface  
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Table 6: HTC Average of the Aluminium Alloy  
Time (s)  
HTC-square (W/m2K)  
HTC-plate  
HTC-cylindrical (axial)  
(W/m2K)  
(W/m2K)  
6.7  
10  
20  
30  
40  
50  
60  
70  
80  
90  
6.2  
6.9  
13.3  
18.3  
44.5  
31.3  
49.2  
91.0  
76.2  
91.4  
75.8  
22.8  
153.2  
134.2  
113.9  
183.6  
73.7  
13.8  
13.9  
21.3  
21.4  
29.4  
29.4  
37.9  
37.9  
47.2  
46.9  
56.5  
53.3  
66.4  
60.2  
156.9  
180.9  
206.0  
233.7  
266.8  
304.2  
346.6  
131.6  
67.5  
100  
110  
120  
130  
140  
150  
88.8  
169.9  
188.4  
236.1  
211.2  
238.8  
98  
ave  
Considering the average of HTC presented in Table 6, HTC required for casting of aluminium alloy was at  
131.6, 73.7 and 98 W/m2K after 150 seconds in rectangular plate, square and cylindrical shapes. However, the  
liquid thermal conductivity (k) obtained of the material used was at 111.8, 90.1 and 105 W/mK for plate, square  
and cylindrical bar respectively. The average of liquid thermal conductivity was at 102.3 W/mK within the range  
of 85 to 173 W/mK of ASTM Table. The following Figures 6-8 were the cast of rectangular plate, square bar  
and cylindrical bar obtained during the experiment.  
Figure 6: Cast Rectangular Plate  
Figure 7: Cast Square Bar  
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Figure 8: Cast Cylindrical Bar  
DISCUSSION  
The study demonstrated that the shape and size of castings significantly influence solidification behavior,  
thermal gradients, and resultant microstructures. These findings align with established principles of heat transfer  
and solidification theory, validating the experimental methodology. However, limitations such as uniformity in  
mold preparation and potential thermal conductivity variations in the green sand may introduce minor  
inconsistencies.  
CONCLUSSIONS  
This study investigates the solidification behaviour and heat transfer characteristics of aluminium alloy 6061  
castings using green sand moulds. Various casting shapes, including rectangular plates, square bars, and  
cylindrical bars, were evaluated to determine the impact of geometry on solidification time, heat transfer  
coefficient (HTC), and the resulting microstructure. The aluminium alloys 6061 are cast-able using green sand  
mould with Heat transfer coefficient (HTC) in the cast objects obtained as 101.1 W/m2K. The findings reveal  
that lower modulus shapes, such as the rectangular plate, solidified faster due to a higher surface area-to-volume  
ratio, leading to a higher HTC and finer microstructure. Conversely, shapes like the cylindrical bar, with lower  
HTC and slower solidification, exhibited coarser microstructures. The results emphasize the needs of heat  
transfer coefficient for understanding solidification and cooling process in Al6061 casting adoptable in industrial  
application.  
REFERENCES  
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