Studying the parameters effecting the production of al-alloy composite materials by squeeze casting

Dissertant

Muhammad, Usamah Sultan

University

University of Technology

Faculty

-

Department

Department of Production Engineering and Metallurgy

University Country

Iraq

Degree

Ph.D.

Degree Date

2008

English Abstract

Squeeze casting is a pressure casting process .n which molten metal is solidified under the direct action of a pressure.

In squeeze casting, the relationship between the process parameters and the quality of the squeeze cast components is not fully understood ; thus the need for more studies in this area of technology for better understanding of the process.

The present work encompasses studying the effect of direct squeeze casting process parameters on the production of (3 and 20 %) volume fraction carbon fibers (CF) reinforced Al-Si matrix composites and 12% volume fraction graphite particles (GP) reinforced Al-Si matrix composites.

The evaluated process parameters are squeeze pressure in the range (7,5-53) MPa, die preheating temperature (100,200,300) °C, pouring temperature (700, 780)°C for the CF / Al-Si composites and (620,700,780)°C for the GP/Al-Si composites, squeeze time (30 sec), and delay time (5 sec).

A detailed microstructure was examined for the two types of composites.

Density, porosity, hardness, tensile strength and wear rate are also evaluated to reach the better combination of process parameters that give the better properties.

The results show that the squeeze casting have verconied the wettability problems for all the produced composites and also overcomed the heat diffusivity problems in the GP / Al-Si composites.

The results show a refinement in the microstructure for both types of composites compared to the non-reinforced alloy, and a good distribution of the matrix between the carbon fibers for the CF / Al-Si composites when using higher casting pressures of (38 and 53MPa), lower pouring temperature of (700T) for CF / Al-Si composites and (620 and 700°C) for GP / Al-Si composites, and lower die temperatures of (100 and 200°C).

Also a good bonding results between the reinforcements and the matrix at all used parameters for both types of composites.

The using of very low pressure of (7.5MPa), pouring temperature of (700°C) and die temperature of (100°C) caused an agglomeration in the carbon fibers without liquid penetration.

Increasing the carbon fibers volume fraction had led to increasing the microstructure refinement, hardness, tensile strength but also increasing porosity and decreasing density.

The difference in each property results was little at all of squeeze casting parameters.

The density of composites is increased at higher used pressures of (38 and 53) MPa, (700°C) pouring temperature and (200°C) die temperature due to the effect of decreasing shrinkage defects and segregation under these conditions.

The density - squeeze casting pressure relationship behavior have proved the densification mechanism of the squeeze casting process and it depend primarily on the process more than the produced material.

The hardness for both types of composites is increased to (84 VHN) for CF/Al-Si composites and to (125 VHN) for GP / Al-Si composites by using the above conditions when compared to the hardness of the non-reinforced Al-Si alloy which was (61 VHN).

The using of higher pressure (53MPa), lower pouring temperature (700° C), and lower die temperature (200°C) have increased the ultimate tensile strength of the CF /Al-Si composites to (183MPa) when compared to that of the non- re in forced alloy which was (168MPa) because of the increased bonding, decreased shrinkage defects and fibers degradation based on the results.

Also, UTS is increased at P=38MPa, Tp = 700°C, and Td = 100°C.

At all other squeeze casting parameters, the tensile strength is decreased at different percentages due to fibers degradation caused by the formation of AI4C3 phase in higher amount based on the results.

The wear rate of all the graphite particles reinforced Al-Si matrix composites is reduced at alt the squeeze casting parameters when compared to that of the 11 on -rein forced alloy which was (12.6* 10-9 cm3/cm) due to the existence of graphite particles which act as a lubrication agent.

Also the decrease was due to the good bonding of these particles with the matrix alloy, The lower wear rate was (6.14*10-9 cm3/cm) at P = 53MPa.

Tp = 700°C, and Td = 200°C.

The results show that the hetter parameters for the production of carbon fibers reinforced Al-Si matrix composites and graphite particles reinforced Al-Si matrix composites are (38 and 53 MPa) squeeze pressures, (200°C) die preheating temperature and (700°C) pouring temperature due to the better properties resulting from using these parameters.

Main Subjects

Materials Science , Minerals

Topics

• Composite materials
• Minerals
• Aluminum castings
• Metal castings

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305659