On the nature of high pressure die casting die failures


B. Zabala (a)*, A. Igartua (a), F. Pagano (a) , M. Conte (a), Harald Eibisch (b), Ruben Heid (c)
(a) IK4-TEKNIKER, Tribology Department
(b) AUDI AG Ingolstadt, Technologieentwicklung Gießen
(c) Technische Universität Braunschweig, Institut für Füge- und Schweißtechnik

e-mail: borja.zabala@tekniker.es

 

ABSTRACT -  Copyright 2014 World Foundry Organization
 

High pressure die casting (HPDC) is a single step and high production rate manufacturing process of light alloy castings. The resulting pieces have close dimensional tolerances and smooth surface finish. HPDC is a much cost efficient method, however, the maintenance and initial costs of the mould (around 20% of the total) limits the competitiveness of the process seriously.
Another limit is due to wear of the devices, therefore, a better understanding of the nature of the wear mechanisms and the main parameters affecting them are needed.
In this document, the main wear mechanism related to HPDC, such as thermal fatigue, erosion, die soldering and corrosive wear are analyzed according to literature.


KEYWORDS
. die failure, thermal fatigue, die soldering, erosion, corrosion, washout

 

 

The Influence of Cr content on the Fe-rich phase Formation and
Impact toughness of a Die-cast AlSi9Cu3(Fe) alloy

G. Timelli, S. Ferraro, A. Fabrizi, S. Capuzzi, F. Bonollo
University of Padova – Dep. of Management and Engineering, Vicenza, Italy
L. Capra, G.F. Capra
Raffineria Metalli Capra S.p.A., Castel Mella (BS), Italy


ABSTRACT -  Copyright 2014 World Foundry Organization

 

The influence of chromium on the microstructure and impact toughness of high-pressure die-cast AlSi9Cu3(Fe) alloy was investigated systematically as the content of Cr was varied. The results indicate that, with the increase of Cr content, the area fraction of primary (sludge) and secondary (proeutectic) -Alx(Fe,Mn,Cr)ySiz intermetallic compounds increase. Moreover, the sludge morphology
evolves from polyhedral to branched or star-like shapes while the secondary Fe-rich particles seem  to not be morphologically affected. The polyhedral sludge particles are associated to a regular rhombic dodecahedron, while the star-like and branched morphologies originate from hollowed rhombic dodecahedron. From the load–deflection curves, the impact toughness (Wt)and maximum load absorbed by the specimens (Fm) during impact testing were measured. The mechanical
tests reveal that Wt and Fm values are almost constant up to 0.12wt.% Cr content achieving about 15.7 J and 9.3 kN, respectively, while a further addition of Cr ( 0.15 wt.%) leads a overall performance decrease higher than 9%.


KEYWORDS: Aluminium alloys; Chromium; Microstructure; Impact properties; High-pressure diecasting;
Intermetallic compounds; Sludge

Development of Heat Treatments for Automotive Components die-cast with Secondary Aluminium Alloy at Semi-Solid state

S. Capuzzi, S. Ferraro, G. Timelli,
University of Padova – Dep. of Management and Engineering, Vicenza, Italy
L. Capra, G.F. Capra
Raffineria Metalli Capra S.p.A., Castel Mella (BS), Italy
Iñigo Loizaga
Fundation CIE, Vizcaya (Bilbao), Spain.


ABSTRACT -  Copyright 2014 World Foundry Organization

 

A great contribution to the use of aluminium alloys comes from improvements in casting process. High-pressure diecasting allow to increase production and permit to realise complex-shaped castings with thin wall thickness. This is possible because the molten metal is injected at high velocity inside the die cavity and then it rapidly solidifies. However, these features reduce the quality of the component due to a substantial amount of air/gas entrapped during the filling phase. This denies the

opportunity for further property enhancement by heat treatment at high temperature. Due to difficulty to produce high integrity die-castings, generally inexpensive secondary alloys are used. In order to eliminate or at least reduce the amount of entrapped porosity, semi-solid metal forming processes have been developed. In this work, the microstructural and mechanical evolutions of an AlSi7Cu3Mg secondary alloy die-cast at semi-solid state by SEED process are investigated over different heat treatment conditions. The spheroidization of eutectic Si, the progressive dissolution of Cu-rich phases and the hardness variations of the alloy were observed and quantified. The results indicate that the mechanical properties increase with the increase of solution temperature. The effects of artificial ageing temperature and time were then studied. By increasing the ageing temperature, the maximum hardness value decreases but it is reached at shorter holding time.

KEYWORDS: Secondary aluminium alloy; Heat treatment; Semi-solid; Microstructure; Intermetallic compounds; mechanical properties

Knowledge generation for high pressure die casting thermal control: Leidenfrost effect and wettability on lubricant sprying

V. Scapis, Thesis at Padova University, October 2014

ABSTRACT

This graduation thesis deals with the Leidenfrost effect in high-pressure die-casting (HPDC) process, especially during the spraying phase. Lubricant is sprayed in this phase when the die is opened. If the solid surface temperature is much higher than the fluid boiling point, the Leidenfrost effect occurs. Since a vapour film forms a continuous barrier over the die surface, the die lubricant cannot penetrate it. This leads to a higher evaporation time and consequently to a lower energy removal. The aim of this work is to avoid this undesired phenomenon with the study of its variables.

The thesis starts with a description of high-pressure die-casting process, focusing on its phases, types, advantages/disadvantages and products. Afterwards, it focuses on the subject matter of the research, thus on the spraying phase in general giving special attention to lubricants and the effect that occurs with its interaction with the die surface (Leidenfrost effect and wettability). A little description of lubricant types, uses and differences is also included in order to understand, and justify as well, some laboratory choices. An experimental part covers all the subsequent contents.  It explains at first the test device used, attaching similarities and differences with others previously adopted. Secondly the operating procedure is briefly described trying to reproduce as faithfully as possible the real conditions. It is for this necessary point out a gap, since LFP is very dependent on the flux and test flux is very different to the spraying. All the parameters that affect the Leidenfrost temperature and the wettability were tested in laboratory, such as the effect of the type of lubricant, die roughness, die material, oxidation and flux characteristics.

A paper related to this research has been submitted to EUROGUSS 2016 International Die Casting Conference and it has been accepted. Further information will be provide on due course.

Correlation among process parameters and defects in aluminum high pressure diecastings

E. Battaglia, Thesis at University of Padova, July 2014

New innovative sensors to monitor HPDC process

A. Mazzamuto, Thesis at University of Padova, October 2014

Correlation among process paramentes, defects and mechanical properties in Aluminum high pressure diecastings

I. Tonello, Thesis at University of Padova, October 2014

The Effects of Microstructure Heterogeneities and Casting Defects on the Mechanical Properties of High Pressure Die CAst AlSi9Cu3(Fe) Alloys

TG. Timelli, A. Fabrizi, Metallurgy and Materials Transations, Springer, 2014

The role of Cr additions and Fe-rich compounds on microstructural features and impact toughness of AlSi9Cu3(fe) diecasting alloys

G. Timelli, A. Fabrizi, S. Capuzzi, F. Bonollo, Material Science and Engineering, A603 (2014), 58-68

Effect of grain refinement and cooling rate on the microstructural and mechanical properotes of secondary Al-Si-Cu alloys

G. Timelli, G. Camicia, S. Ferraro, Journal of Materials Engineering and Performance, 23 (2), 2014, 611-621

The influence of Fe, Mn and Cr additions on the fomration of iron-rich intermetallic phases in an Al-Si die-casting alloy  

A. Fabrizi, S. Ferraro, G. Timelli, University of Padova – Dep. of Management and Engineering,
Strad. S. Nicola 3; Vicenza, 36100, Italy
Paper presented at the Annual Meeting and Exhibition TMS 2014 in San Diego, California (16-20 February 2014)

KEYWORDS: Al-Si die-casting alloy, primary α-Fe phase, intermetallic morphology

ABSTRACT

The microstructure evolution of a high-pressure die-cast AlSi9Cu3(Fe) alloy is studied over different Fe, Mn and Cr content. Fe-rich intermetallic phases were characterized by using optical microscope, image  analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS). The results  revealed that the amount of Fe-rich phases as well their size increase by increasing the elemental  content. Needle-like particles appear in the alloy with higher Fe:Mn ratio, while coarse α-phases assume polygonal, stark-like or Chinese script morphology according to the Fe:Mn:Cr balance as revealed by EDS analysis. The 3D-SEM investigation suggests that both the polygonal and stark-like morphology can be associated to a rhombic dodecahedron structure. The morphology evolution of the Fe-bearing particles as a function of the chemical composition and casting process is proposed and discussed.

Micrustructure and mechanical properties of automotive components die cast with secondary aluminum alloys by seed semi-solid process

G. Timelli1, S. Capuzzi1, S. Ferraro1, A. Fabrizi1, L. Capra2
1 University of Padova – Dep. of Management and Engineering; Strad. San Nicola 3; Vicenza, 36100, Italy
2 Raffineria Metalli Capra SpA; Via Quinzano 96; Castel Mella (BS), 25030, Italy

Paper presented at the Annual Meeting and Exhibition TMS 2014 in San Diego, California (16-20 February 2014)

KEYWORDS: Aluminum alloys, Semi-solid, SEED, Microstructure, Mechanical properties

ABSTRACT

The microstructure and mechanical properties of an automotive component die-cast by Swirled Enthalpy Equilibration Device process are analyzed. Two secondary aluminum alloys have been used, AlSi7Cu3Mg and AlSi9Cu3(Fe) alloys. The castings have been investigated by means of computer tomography to evaluate the concentration and distribution of casting defects, especially in the regions of thick wall thickness. Microstructural investigation has been carried out by means of optical microscope and image analysis technique. The results reveal a not uniform distribution of primary α-Al globules throughout the casting, with a solid fraction ranging from 48 to 58%, and eutectic segregation phenomena. The castings have been mapped in terms of mechanical properties and quality index. The variation of the mechanical properties reflects the presence of local casting defects and alloying segregation.