Laser Metal Fused Al Alloy Processed Using Different Heat Treatments

AbstractThe effect of cooling rate on the tensile properties of specimens of the Nb-40Ti-15A1 alloy (in at.%) subjected to various heat treatments has been studied. This alloy has the B2 crystal structure and an order-disorder transition temperature between 1020°C and 1100°C. Two heat treatments have been carried out; the first one involves an 1100°C/1hr heat treatment followed by furnace cooling, air cooling or water quenching. The second type of heat treatment involves re-heating the furnace-cooled and water-quenched specimens at 400°C for 10 minutes or 900°C for 30 minutes, followed by either furnace cooling or water quenching. Tensile properties, SEM fractographs and microstructures of these specimens have been assessed. It is shown that specimens furnace-cooled from 1100°C have higher strength and less ductility than the water quenched ones. An observed microstructural feature associated with cooling rates is the difference in anti-phase domain (APD) size. Discussions are focused on possible cooling rate related phenomena that could affect the tensile properties. It is proposed that the degree of long range ordering, not the APD size, is the dominant factor for the observed cooling rate effect on the tensile properties.

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Precipitation in Al-Alloy 6016 – The Role of Excess Vacancies

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.317 ◽

2012 ◽

Vol 706-709 ◽

pp. 317-322 ◽

Cited By ~ 19

Author(s):

Ahmad Falahati ◽

Peter Lang ◽

Ernst Kozeschnik

Keyword(s):

Low Temperatures ◽

Heat Treatments ◽

Excess Vacancy ◽

Al Alloy ◽

Precipitation Sequence ◽

Excess Amount ◽

Superior Mechanical Properties ◽

Basic Features ◽

Novel Model

6xxx Al alloys owe their superior mechanical properties to the precipitation of finely dispersed metastable β´´ precipitates. These particles are formed in the course of optimized heat treatments, where the desired microstructure is generated in a sequence of precipitation processes going from MgSi co-clusters and GP zones to β´´ and β´ precipitates and finally to the stable β and Si diamond phases. The entire precipitation sequence occurs at relatively low temperatures (RT to approx. 200 °C) and is mainly controlled by the excess amount of quenched-in vacancies, which drive the diffusional processes at these low temperatures. Very recently a novel model for the prediction of the excess vacancy evolution controlled by the annihilation and generation of vacancies at dislocation jogs, grain boundaries and Frank loops was developed and implemented in the thermo-kinetic software MatCalc. In the present work, we explore the basic features of this model in the simulation of the excess vacancy evolution during technological heat treatments. The focus of this article lies on the effect of vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.

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Age-Hardening of Rheo-High Pressure Die Cast Al-Alloy 6066

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1019.47 ◽

2014 ◽

Vol 1019 ◽

pp. 47-54

Author(s):

Carlien Taute ◽

Heinrich Möller

Keyword(s):

High Pressure ◽

High Performance ◽

Solution Treatment ◽

Heat Treatments ◽

Hot Tearing ◽

Age Hardening ◽

Al Alloy ◽

Artificial Ageing ◽

One Step ◽

Semi Solid

Al-Mg-Si-Cu alloy 6066 is a heat-treatable wrought alloy that is commonly used in high performance bicycle frames. Wrought alloys are difficult to cast using conventional liquid casting techniques, as hot tearing can occur. However, a method that effectively reduces that risk is rheo-high pressure die casting (R-HPDC). Casting alloy 6066 using semi-solid metal processing makes it possible to be used for near-net shape forming of components. This study investigates the age-hardening response of R-HPDC alloy 6066. The effects of different solution heat treatments, natural pre-ageing and artificial ageing are studied. The different solution heat treatments investigated are a one-step and a two-step solution treatment. The one-step treatment was performed at 530°C only and the two-step treatment at 530°C followed by 550°C. It is shown that natural pre-ageing has a detrimental effect on the T6 properties and that the longer two-step solution heat treatment is justified due to an increase in hardness and prevention of incipient melting. The Vickers hardness in different temper conditions (F, T4, T5 and T6) were determined and compared to the typical hardness values of the alloy in the wrought condition.

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