Roger Lumley - Academia.edu (original) (raw)

Papers by Roger Lumley

Metal Powder Report, 1997

thin diamond coated tools are now commercially available in quantity and are used in a range of i... more thin diamond coated tools are now commercially available in quantity and are used in a range of industies. Applications in machining of graphitic materials, plastics, composites and automotive parts were outlined. MICROSTRUCTURE AND CUTTING PERFORMANCE OF DIAMOND COATED CEMENTED CARBIDE Q. Deng. (Zhuzhou Cemented Carbide Works, China.) It was reported that diamond coatings had been deposited on WC-Co and WC-TiC-Co substrates by hot filament assisted chemical vapour deposition. Films were characterized for structure and adhesion measured by a scratch test. Cutting performance was assessed by turning tests. Small amounts of wear, without flaking, were found when cutting Al-Si and Cu-Sn alloys. Coating was reported to extend tool life by a factor of 5. 1996 WORLD CONGRESS ON POWDER METALLURGY.The abstracts which follow are from papers which were presented at the Congress, which was held in Washington DC,

JOM, 2018

The current article describes the results of a study aimed at developing new compositions of Al-S... more The current article describes the results of a study aimed at developing new compositions of Al-Si-Mg high-pressure die-cast alloys, which display improved ductility in as-cast and heat-treated conditions. Studies of the new alloys, which contain higher than normal Mn contents and lower than normal Fe contents, have shown that compositions generated through the use of recycled wheels made from A356 alloy (''Troma'') may achieve the goals. As-cast, T4 and T6 heat-treated high-pressure die cast compositions have been evaluated. T4 and some T6 tempers are shown to produce an optimal combination of 0.2% proof stress, tensile strength and elongation. Some compositions also require a significantly reduced temperature of solution treatment to generate excellent combinations of mechanical properties. The alloys developed can be considered for structural die castings in modern automotive applications.

International Heat Treatment and Surface Engineering, 2010

High pressure die cast (HPDC) aluminium components that respond to age hardening cannot normally ... more High pressure die cast (HPDC) aluminium components that respond to age hardening cannot normally be solution treated at high temperatures because the presence of internal porosity and entrapped gases leads to the formation of surface blisters. Parts may also become dimensionally unstable due to swelling. These factors that prevent heat treatment present significant limitations to the utilisation of HPDC components. Now it has been found that blistering and dimensional change can be avoided by using much shorter solution treatment times and lower temperatures. Experiments with alloys 360 (Al-9?5Si-0?5Mg) and 380 (Al-8?5Si-3?5Cu) have shown that strong responses to age hardening are still possible following these modified solution treatments. In the current paper, the role of critical alloying elements is considered in both current specification Al-Si-Cu-(X) alloys, and also in newly developed alloy compositions. It is shown that 0?2% proof strengths over 400 MPa may be readily achieved by heat treating conventionally produced die castings.

International Heat Treatment and Surface Engineering, 2009

AbstractHigh pressure die casting (HPDC) is widely used as a cost effective way to mass produce m... more AbstractHigh pressure die casting (HPDC) is widely used as a cost effective way to mass produce metal components that are required to have close dimensional tolerances and smooth surface finishes, accounting for ∼50% of the aluminium castings produced worldwide. These components are not considered to be heat treatable by conventional means because the high temperatures involved with solution treatment cause surface blistering and dimensional instability. A new heat treatment procedure involving a truncated solution treatment at lower than conventional temperatures alleviates this problem and can significantly improve mechanical properties, in many cases, doubling the 0·2% proof strength after artificial (T6) aging. This may enable current HPDC parts to be redesigned to use less metal while still achieving the required performance. The cost of heat treatment can be easily offset by the reduction in metal content and productivity improvements which result in an overall lower cost of the part. The new proces...

Materials Science and Technology, 2005

Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwel... more Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwell period at lower temperature, higher values of tensile properties and fracture toughness may be achieved than are possible with single stage T6 tempers. A second interrupted aging cycle has now been developed that involves underaging at the elevated temperature, quenching, and then allowing secondary precipitation to occur at, or just above, room temperature. Designated a T6I4 (I5interrupted) temper by the authors, this simpler aging cycle may reduce heat treatment costs. Tests on some 30 cast and wrought alloys have resulted in tensile properties close to those for a T6 temper, with higher values of fracture toughness being recorded for some cases. Such an aging treatment can be incorporated into a paint bake cycle to simplify the heat treatment of coated automotive components.

Materials Science Forum, 2002

Fundamentals of Aluminium Metallurgy, 2011

Materials Science Forum, 2006

This paper reviews some of the practical outcomes of exploiting secondary precipitation during th... more This paper reviews some of the practical outcomes of exploiting secondary precipitation during the heat treatment of aluminium alloys and discusses current understanding of this phenomenon. Recent studies have utilised the techniques of positron annihilation spectroscopy (PAS), 3D atom probe (3DAP) as well as the more traditional transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) to investigate early precipitation events that occur during secondary ageing at low temperatures (~20-65°C). This work has confirmed that clustering and GP zone formation can modify the nature and distribution of precipitates that form when ageing is subsequently resumed at more elevated temperatures. Prospects for achieving further improvements in heat treatment schedules and alloy compositions to take greater advantage of secondary precipitation are also considered.

Springer Series in Materials Science, 2007

ABSTRACT

Materials Science Forum, 2010

Recently, heat treatment technologies have been developed by the CSIRO Light Metals Flagship in A... more Recently, heat treatment technologies have been developed by the CSIRO Light Metals Flagship in Australia that allow the 0.2% proof stress of conventional aluminum alloy high pressure diecastings (HPDC’s) to be more than doubled without encountering problems with blistering or dimensional instability [1,2]. A range of other properties may also be improved such as fatigue resistance, thermal conductivity and fracture resistance. However, the current commercial HPDC Al-Si-Cu alloys have not been developed to exploit heat treatment or to optimize these specific mechanical properties, and one potential limitation of heat treating HPDC’s is that fracture resistance may be reduced as strength is increased. The current paper presents the outcomes of a program aimed at developing highly castable, secondary Al-Si-Cu HPDC alloys which display significantly enhanced ductility and fracture resistance in both the as-cast and heat treated conditions. Kahn-type tear tests were conducted to compare...

Scripta Materialia, 1996

ExDerimental Methods Three binary lsystems were examined: Al-Sri, Al-Zn, and Al-Cu. Starting addi... more ExDerimental Methods Three binary lsystems were examined: Al-Sri, Al-Zn, and Al-Cu. Starting additive powders were either < 45pm in size or 125-150pm. The ahnninium powder was air atomized, passed through a 100 mesh screen and had an average particle size (dTO) of 60um. All powders had a purity >99.5%. Alloy compositions (weight%) were Al-SSn, Al-lOZn, and Al-5.5Cu. All alloys had 1% stearic acid added as 589 590 THE EFFECT OF SOLUBILITY Vol. 35, No. 5 TABLE 1 Sir&ring Cycles Alloy sysren1 Al-al Sinlcring Cycle 2S"C-?5O"C at I. IO Sr JO"/nlin., held 20 mins. for tlewnxing then hcatetl ;II I, 10 & 4O"/n~in. (renpeclively) to 620°C. and held for IO mills. AI-CU 25"C-?So'C at IW/min., held 20 mills. for &waxing then heated at I0"lmin. to 6oI)"C. and hcltl for JO mins. AI-Sn 2S"C-200°C at IO"/min., held 20 mins. for dewaxing thcu hentcd at IO"/min. to 600°C. an11 heltl for one llllllr.

Scripta Materialia, 2006

ABSTRACT

Metallurgical and Materials Transactions A, 1999

Metallurgical and Materials Transactions A, 2007

High-pressure die-cast Al alloys cannot normally be heated at high temperatures due to the presen... more High-pressure die-cast Al alloys cannot normally be heated at high temperatures due to the presence of pores containing entrapped gases, which lead to the formation of surface blisters. It has been found that blistering can be avoided by using considerably shorter solution-treatment times and lower temperatures. Experiments with alloys 360 (Al-9.5Si-0.5Mg) and 380 (Al-8.5Si-3.5Cu) have shown that strong responses to

The 12th …, 2011

Vickers microhardness cross sectional maps of cast-to-shape flat specimens 3 mm thick were determ... more Vickers microhardness cross sectional maps of cast-to-shape flat specimens 3 mm thick were determined for the (mass %) Al-9Si-2Cu-0.3Mg and Al-5Mg-2Si-Mn high pressure die cast alloys. Higher hardness numbers were generally obtained near the casting surface, the ...

Acta Materialia, 2007

ABSTRACT Interruption of a conventional T6 heat treatment at 177 °C for the Al–Mg–Si–Cu alloy 606... more ABSTRACT Interruption of a conventional T6 heat treatment at 177 °C for the Al–Mg–Si–Cu alloy 6061 after a short period of time (20 min), by inserting a dwell period at a lower temperature (e.g. 65 °C), promotes secondary precipitation of Guinier–Preston (GP) zones. As a consequence, a much greater number of precursors to the β″ precipitates are produced so that a finer and denser dispersion of this phase is formed when T6 ageing is resumed. This change in microstructure causes significant and simultaneous improvements in tensile properties and fracture toughness. Secondary precipitation of GP zones occurs through a gradual evolution of a large number of Mg–Si(–Cu)-vacancy co-clusters formed during the initial ageing at 177 °C. The precise mechanism of secondary precipitation has been revealed by three-dimensional atom probe microscopy supplemented by transmission electron microscopy and differential scanning calorimetry.

Acta Materialia, 2002

Tests at 130°C and 150°C have shown that the creep resistance of an Al-Cu-Mg-Ag alloy is signific... more Tests at 130°C and 150°C have shown that the creep resistance of an Al-Cu-Mg-Ag alloy is significantly increased if it is heat-treated at an elevated temperature to an underaged condition rather than the fully hardened, T6 temper. This beneficial effect of underageing is manifest in reduced rates of secondary creep. Similar results have been obtained for the commercial alloy 2024. Delays at ambient temperature after underageing and before testing lead to secondary precipitation and a progressive decrease in creep performance that eventually reverts to close to that for the T6 condition. This detrimental effect may be overcome by slow cooling from the underageing temperature, which arrests or impedes subsequent secondary precipitation. Microstructural observations suggest that the enhanced creep resistance in the underaged condition is a consequence of the presence of "free" solute in solid solution that is not yet involved in precipitation.

Metal Powder Report, 1997

thin diamond coated tools are now commercially available in quantity and are used in a range of i... more thin diamond coated tools are now commercially available in quantity and are used in a range of industies. Applications in machining of graphitic materials, plastics, composites and automotive parts were outlined. MICROSTRUCTURE AND CUTTING PERFORMANCE OF DIAMOND COATED CEMENTED CARBIDE Q. Deng. (Zhuzhou Cemented Carbide Works, China.) It was reported that diamond coatings had been deposited on WC-Co and WC-TiC-Co substrates by hot filament assisted chemical vapour deposition. Films were characterized for structure and adhesion measured by a scratch test. Cutting performance was assessed by turning tests. Small amounts of wear, without flaking, were found when cutting Al-Si and Cu-Sn alloys. Coating was reported to extend tool life by a factor of 5. 1996 WORLD CONGRESS ON POWDER METALLURGY.The abstracts which follow are from papers which were presented at the Congress, which was held in Washington DC,

JOM, 2018

The current article describes the results of a study aimed at developing new compositions of Al-S... more The current article describes the results of a study aimed at developing new compositions of Al-Si-Mg high-pressure die-cast alloys, which display improved ductility in as-cast and heat-treated conditions. Studies of the new alloys, which contain higher than normal Mn contents and lower than normal Fe contents, have shown that compositions generated through the use of recycled wheels made from A356 alloy (''Troma'') may achieve the goals. As-cast, T4 and T6 heat-treated high-pressure die cast compositions have been evaluated. T4 and some T6 tempers are shown to produce an optimal combination of 0.2% proof stress, tensile strength and elongation. Some compositions also require a significantly reduced temperature of solution treatment to generate excellent combinations of mechanical properties. The alloys developed can be considered for structural die castings in modern automotive applications.

International Heat Treatment and Surface Engineering, 2010

High pressure die cast (HPDC) aluminium components that respond to age hardening cannot normally ... more High pressure die cast (HPDC) aluminium components that respond to age hardening cannot normally be solution treated at high temperatures because the presence of internal porosity and entrapped gases leads to the formation of surface blisters. Parts may also become dimensionally unstable due to swelling. These factors that prevent heat treatment present significant limitations to the utilisation of HPDC components. Now it has been found that blistering and dimensional change can be avoided by using much shorter solution treatment times and lower temperatures. Experiments with alloys 360 (Al-9?5Si-0?5Mg) and 380 (Al-8?5Si-3?5Cu) have shown that strong responses to age hardening are still possible following these modified solution treatments. In the current paper, the role of critical alloying elements is considered in both current specification Al-Si-Cu-(X) alloys, and also in newly developed alloy compositions. It is shown that 0?2% proof strengths over 400 MPa may be readily achieved by heat treating conventionally produced die castings.

International Heat Treatment and Surface Engineering, 2009

AbstractHigh pressure die casting (HPDC) is widely used as a cost effective way to mass produce m... more AbstractHigh pressure die casting (HPDC) is widely used as a cost effective way to mass produce metal components that are required to have close dimensional tolerances and smooth surface finishes, accounting for ∼50% of the aluminium castings produced worldwide. These components are not considered to be heat treatable by conventional means because the high temperatures involved with solution treatment cause surface blistering and dimensional instability. A new heat treatment procedure involving a truncated solution treatment at lower than conventional temperatures alleviates this problem and can significantly improve mechanical properties, in many cases, doubling the 0·2% proof strength after artificial (T6) aging. This may enable current HPDC parts to be redesigned to use less metal while still achieving the required performance. The cost of heat treatment can be easily offset by the reduction in metal content and productivity improvements which result in an overall lower cost of the part. The new proces...

Materials Science and Technology, 2005

Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwel... more Earlier work has shown that, if the artificial aging of aluminium alloys is interrupted by a dwell period at lower temperature, higher values of tensile properties and fracture toughness may be achieved than are possible with single stage T6 tempers. A second interrupted aging cycle has now been developed that involves underaging at the elevated temperature, quenching, and then allowing secondary precipitation to occur at, or just above, room temperature. Designated a T6I4 (I5interrupted) temper by the authors, this simpler aging cycle may reduce heat treatment costs. Tests on some 30 cast and wrought alloys have resulted in tensile properties close to those for a T6 temper, with higher values of fracture toughness being recorded for some cases. Such an aging treatment can be incorporated into a paint bake cycle to simplify the heat treatment of coated automotive components.

Materials Science Forum, 2002

Fundamentals of Aluminium Metallurgy, 2011

Materials Science Forum, 2006

This paper reviews some of the practical outcomes of exploiting secondary precipitation during th... more This paper reviews some of the practical outcomes of exploiting secondary precipitation during the heat treatment of aluminium alloys and discusses current understanding of this phenomenon. Recent studies have utilised the techniques of positron annihilation spectroscopy (PAS), 3D atom probe (3DAP) as well as the more traditional transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) to investigate early precipitation events that occur during secondary ageing at low temperatures (~20-65°C). This work has confirmed that clustering and GP zone formation can modify the nature and distribution of precipitates that form when ageing is subsequently resumed at more elevated temperatures. Prospects for achieving further improvements in heat treatment schedules and alloy compositions to take greater advantage of secondary precipitation are also considered.

Springer Series in Materials Science, 2007

ABSTRACT

Materials Science Forum, 2010

Recently, heat treatment technologies have been developed by the CSIRO Light Metals Flagship in A... more Recently, heat treatment technologies have been developed by the CSIRO Light Metals Flagship in Australia that allow the 0.2% proof stress of conventional aluminum alloy high pressure diecastings (HPDC’s) to be more than doubled without encountering problems with blistering or dimensional instability [1,2]. A range of other properties may also be improved such as fatigue resistance, thermal conductivity and fracture resistance. However, the current commercial HPDC Al-Si-Cu alloys have not been developed to exploit heat treatment or to optimize these specific mechanical properties, and one potential limitation of heat treating HPDC’s is that fracture resistance may be reduced as strength is increased. The current paper presents the outcomes of a program aimed at developing highly castable, secondary Al-Si-Cu HPDC alloys which display significantly enhanced ductility and fracture resistance in both the as-cast and heat treated conditions. Kahn-type tear tests were conducted to compare...

Scripta Materialia, 1996

ExDerimental Methods Three binary lsystems were examined: Al-Sri, Al-Zn, and Al-Cu. Starting addi... more ExDerimental Methods Three binary lsystems were examined: Al-Sri, Al-Zn, and Al-Cu. Starting additive powders were either < 45pm in size or 125-150pm. The ahnninium powder was air atomized, passed through a 100 mesh screen and had an average particle size (dTO) of 60um. All powders had a purity >99.5%. Alloy compositions (weight%) were Al-SSn, Al-lOZn, and Al-5.5Cu. All alloys had 1% stearic acid added as 589 590 THE EFFECT OF SOLUBILITY Vol. 35, No. 5 TABLE 1 Sir&ring Cycles Alloy sysren1 Al-al Sinlcring Cycle 2S"C-?5O"C at I. IO Sr JO"/nlin., held 20 mins. for tlewnxing then hcatetl ;II I, 10 & 4O"/n~in. (renpeclively) to 620°C. and held for IO mills. AI-CU 25"C-?So'C at IW/min., held 20 mills. for &waxing then heated at I0"lmin. to 6oI)"C. and hcltl for JO mins. AI-Sn 2S"C-200°C at IO"/min., held 20 mins. for dewaxing thcu hentcd at IO"/min. to 600°C. an11 heltl for one llllllr.

Scripta Materialia, 2006

ABSTRACT

Metallurgical and Materials Transactions A, 1999

Metallurgical and Materials Transactions A, 2007

High-pressure die-cast Al alloys cannot normally be heated at high temperatures due to the presen... more High-pressure die-cast Al alloys cannot normally be heated at high temperatures due to the presence of pores containing entrapped gases, which lead to the formation of surface blisters. It has been found that blistering can be avoided by using considerably shorter solution-treatment times and lower temperatures. Experiments with alloys 360 (Al-9.5Si-0.5Mg) and 380 (Al-8.5Si-3.5Cu) have shown that strong responses to

The 12th …, 2011

Vickers microhardness cross sectional maps of cast-to-shape flat specimens 3 mm thick were determ... more Vickers microhardness cross sectional maps of cast-to-shape flat specimens 3 mm thick were determined for the (mass %) Al-9Si-2Cu-0.3Mg and Al-5Mg-2Si-Mn high pressure die cast alloys. Higher hardness numbers were generally obtained near the casting surface, the ...

Acta Materialia, 2007

ABSTRACT Interruption of a conventional T6 heat treatment at 177 °C for the Al–Mg–Si–Cu alloy 606... more ABSTRACT Interruption of a conventional T6 heat treatment at 177 °C for the Al–Mg–Si–Cu alloy 6061 after a short period of time (20 min), by inserting a dwell period at a lower temperature (e.g. 65 °C), promotes secondary precipitation of Guinier–Preston (GP) zones. As a consequence, a much greater number of precursors to the β″ precipitates are produced so that a finer and denser dispersion of this phase is formed when T6 ageing is resumed. This change in microstructure causes significant and simultaneous improvements in tensile properties and fracture toughness. Secondary precipitation of GP zones occurs through a gradual evolution of a large number of Mg–Si(–Cu)-vacancy co-clusters formed during the initial ageing at 177 °C. The precise mechanism of secondary precipitation has been revealed by three-dimensional atom probe microscopy supplemented by transmission electron microscopy and differential scanning calorimetry.

Acta Materialia, 2002

Tests at 130°C and 150°C have shown that the creep resistance of an Al-Cu-Mg-Ag alloy is signific... more Tests at 130°C and 150°C have shown that the creep resistance of an Al-Cu-Mg-Ag alloy is significantly increased if it is heat-treated at an elevated temperature to an underaged condition rather than the fully hardened, T6 temper. This beneficial effect of underageing is manifest in reduced rates of secondary creep. Similar results have been obtained for the commercial alloy 2024. Delays at ambient temperature after underageing and before testing lead to secondary precipitation and a progressive decrease in creep performance that eventually reverts to close to that for the T6 condition. This detrimental effect may be overcome by slow cooling from the underageing temperature, which arrests or impedes subsequent secondary precipitation. Microstructural observations suggest that the enhanced creep resistance in the underaged condition is a consequence of the presence of "free" solute in solid solution that is not yet involved in precipitation.