Metal injection moulding method

a metal injection and moulding technology, applied in the direction of coatings, etc., can solve the problems of difficult use of aluminum in metal injection moulding, achieve the effects of improving the wetting characteristics and sintering behaviour of aluminium, promoting the formation of aluminium nitride, and rapid conversion of aluminium

Inactive Publication Date: 2010-07-22
QUEENSLAND THE UNIV OF
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Benefits of technology

[0030]Tin melts at 232° C., which is considerably lower than that of aluminium (660° C.) and there are no intermetallic phrases. Tin is sparingly soluble in solid aluminium: the maximum solid solubility is less than 0.15%. Aluminium is completely miscible in liquid tin and no immiscible liquids form. Further, the surface tension of liquid tin is significantly less than that of aluminium and trace amounts of tin have been shown by the present inventors to improve the wetting characteristics and sintering behaviour of aluminium. For these reasons, tin is an especially preferred sintering aid.
[0031]The sintering step is conducted in a nitrogen atmosphere. Without wishing to be bound by theory, the present inventors have postulated that conducting the sintering step in a nitrogen atmosphere may promote the formation of aluminium nitride. The present inventors have postulated that forming al

Problems solved by technology

However, aluminium is difficult to use in metal injection moulding because the adherent aluminium oxide f

Method used

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Embodiment Construction

[0057]A variety of alloy and powder compositions, particle sizes and particle shapes were tested. Spherical AA6061 powders with a D50 of 10 μm and spherical Sn with a particle size 82 m were preferred. The metal injection moulding feedstock consisted of 6061 powder with 2 wt % Sn and a binder system of 3 wt % stearic acid, 52wt % palm oil wax and 45 wt % high density polyethylene. The raw materials were mixed at 165° C. for 180 minutes. After granulating, the feedstock was injection moulded into standard tensile bars using an Arburg moulding machine. Solvent debinding was conducted in hexane at 40° C. for 24 hours. The removal of the remaining binder and sintering were combined and conducted in a sealed tube furnace. The preferred atmosphere is high purity nitrogen gas flowing at 1 litre / min. The thermal profile used in the experimental work is shown in Table 1. Magnesium bars were placed around the article during sintering.

[0058]Tensile testing was conducted on as-sintered material...

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Abstract

A method for forming an article by metal injection moudling of aluminium or an aluminium alloy. The method comprises the steps of forming a mixture containing an aluminium powder or an aluminum alloy powder or both and optionally ceramic particles, a binder, and a sintering aid comprising a low melting point metal. The mixture is injection moulded and the binder is removed to form a green body. The green body is sintered. The sintering is conducted in an atmosphere containing nitrogen and in the presence of an oxygen getter.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a metal injection moulding method.BACKGROUND TO THE INVENTION[0002]Metal injection moulding involves the mixing of powder metal with a binder to form a feedstock. This mixture is then injection moulded using injection moulding equipment that is similar to that used in the plastics industry. This forms a “green body”. The green body has sufficient rigidity and strength to enable handling. The green body is then further treated to remove the binder and to sinter the metal powder particles to form the final article.[0003]The binder typically comprises one or more thermoplastic compounds, plasticisers and other organic material. Ideally, the binder is molten or liquid at the injection moulding temperature but solidifies in the mould when the green body is cooled. The feedstock may be converted into solid pellets, for example by granulation. These pellets may be stored and fed into the injection moulding machine at a later time...

Claims

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Application Information

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IPC IPC(8): B22F3/10
CPCB22F3/1007B22F3/1025B22F3/225B22F2999/00C22C1/0416B22F2201/02B22F2201/40
Inventor LIU, ZHENYUNSERCOMBE, TIMOTHY BARRYSCHAFFER, GRAHAM BARRY
Owner QUEENSLAND THE UNIV OF
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