0301-4

7/28/2019 0301-4

1/7

Modeling the Heat Treatment Response of P/M Components

Research TeamMakhlouf M. Makhlouf, Professor

Richard D. Sisson, Jr., ProfessorJiankun Yuan, Research Associate

Virendra S. Werke, PhD Student

Focus Group MembersSim Narasimhan Hoeganaes

Bill Jandeska General MotorsSylvain St-Laurent Quebec Metal Powders, Ltd.

Lorenz Sigl (co-chair) Sinterstahl G.m.b.H.Jean Lynn (chair) DaimlerChrysler Corperation

IntroductionP/M components experience considerable changes during heat treatment that include

changes in mechanical properties, in dimensions, in magnitude and sense of residualstresses, and in metallurgical phase composition. Since the quality assurances criteria

that heat-treated P/M components must meet include prescribed minimum mechanicalproperties and compliance with dimensional tolerances, it is necessary for P/M producers

to be able to accurately predict these changes in order to take appropriate measures toprevent their harmful effects and insure the production of good quality parts. Satisfactory

response to heat treatment is often gauged by the ability of the component to be heat

treated to a desired microstructure, hardness and strength level without undergoingcracking, distortion or excessive dimensional changes.

In addition to the completely reversible changes caused by thermal expansion andcontraction, metallic components experience other permanent dimensional changes

during heat treatment. These permanent changes can be classified into three groups basedon their origin:

(1)Dimensional changes with mechanical origins, these include dimensional changescaused by stresses developed by external forces, dimensional changes arising

from thermally induced stresses, and dimensional changes caused by relaxation ofresidual stresses.

(2)Dimensional changes with metallurgical origins, these include dimensionalchanges caused by recrystallization, solution and precipitation of alloyingelements, and phase transformations.

(3)Dimensional changes due to quenching, these are dimensional changes that occurduring quenching or that result from stresses induced by quenching.

Residual stresses often adversely affect the mechanical properties of P/M components.They are caused by differing rates of cooling during quenching and depend on the

7/28/2019 0301-4

2/7

differential rate of cooling, section thickness, and material strength. Decreasing theseverity of the quench results in a lower level of residual stresses but with a

correspondingly reduced material strength of solution heat-treated materials. Residualstresses may also arise from phase transformations during heat treatment that result in

differential volumetric changes in the material.

ObjectiveThe main objective of this project is to develop and verify a computer simulation

software and strategy that enables the prediction of the effects of heat treatment onpowder metallurgy components. The simulation will accurately predict dimensional

change and distortion, residual stresses, type and quantity of metallurgical phases in themicrostructure, and hardness.

Research Plan

Commercially available software will be chosen for the project. At this time, Dante,which is a finite element based CAE tool for analyzing metal heat treatment processesand marketed by DCT, Inc. is the software of choice. This software can perform all the

required simulations, but its materials properties database was not designed for P/M.Consequently, Phase I of the project will focus on assessing the capabilities of Dante and

the possibility of adapting it to the specifics of powder metallurgy. Once, this isaccomplished, Phase II of the project will commence and will focus on using the

modified software to predict the heat treatment response of powder metallurgycomponents. The predicted responses will be compared to experimentally measured

responses and a modeling/prediction strategy will be formulated and recommendationswill be made to the consortium members. In the early phases of the project, the heated

part will be a simple right cylinder. At later phases of the project production parts chosenby the focus group may be modeled.

MethodologyThe project will be divided into two phases as follows:

PHASE I: ASSESSMENT OF DANTES CAPABILITIES AND THE POTENTIAL OF ADAPTING

IT TO P/M COMPONENTS

Task 1: Assessment of Dantes ability to predict heat treatment response in fully dense

components.

Subtask1.1: Computer simulationsDante will be used to numerically simulate the heating and quenching processes on a 3D

fully dense circular cylinder made from 5160 carbon steel for which a comprehensivematerial properties data set is available.

7/28/2019 0301-4

3/7

Input to Dante will include the 3D geometry model and finite element grid, materialproperties, and heat treatment schedule.

Output from Dante will include

(1) Resultant volume fraction of metallurgical phases.(2)

Hardness distribution after heat treatment.(3) Dimensional changes and distortion.

(4) Magnitude and sense of residual stresses.Subtask 1.2: Experiments and measurements

Dantes predictions will be verified by comparing them to measurements ofcorresponding parameters for specimens obtained using processing conditions similar to

those used in the simulations.

Measurement of dimensional changes and distortionA Starrett coordinate measuring machine will be used to measure the dimensional

changes and distortion caused by the heat treatment process. Sufficient measurementswill be made to obtain accurate representation of the part before and after heat treatment.

Coordinate measuring machines are a fast, accurate and more convenient alternative toconventional methods for measuring complex parts.

Measurement of residual stresses

The standard x-ray diffraction method for measuring residual stress in metalliccomponents will be used. Line shifts due to a uniform strain in the component is

measured and then the stress in the component is determined either by a calculationinvolving the elastic constants of the material or by a calibration procedure involving

measurement of the strain produced by known stresses.

Measurement of volume fraction of metallurgical phasesStandard metallographic sample preparation techniques will be used to prepare specimens

from the heat-treated components. Samples will be prepared from three different cross-sections of the cylinder that are equally spaced along the length of the cylinder. Optical

and scanning electron microscopy together with automated image analysis and energydisperssive x-rays will be used to characterize and quantify the various phases in the

specimens.

Measurement of hardnessStandard Rockwell hardness and microhardness measurements will be performed on the

heat-treated cylinders. Measurements will be performed across three different cross-sections of the cylinder that are equally spaced along the length of the cylinder.

Task 2: Adapt Dante to P/M components

Once Dantes predictions are validated for fully dense components, the software will beused to model the heat treatment response of 5160 carbon steel P/M components that

have low green density. In this case, a critical input to the model is material propertiesthat accurately reflect the properties of porous 5160 carbon steel. Development of this

7/28/2019 0301-4

4/7

database will be a major focus of this Task. The team at WPI will work with the softwareproducers to develop a reliable properties database for porous P/M processed 5160 and

8620 steels and 601AB aluminum alloy.

PHASE II: MODELING THE EFFECT OF VARIOUS PROCESS PARAMETERS ON THE HEATTREATMENT RESPONSE OF P/M PARTS

Task 1: Computer simulationsComputer simulation of the heat treatment response of cylinders made from 5160 and

8620 steels as well as 601AB alloy will be performed as described in subtasks 1.1 to 1.3.

Subtask 1.1: Computer simulation of the heat treatment response of 5160 steelDante will be used to predict the heat treatment response, i.e., distortion, residual stress,

hardness, and microstructure evolution in a 5160 carbon steel cylinder for combinationsof the following conditions:

Green density: (1) Low density, (2) full density, and (3) highly variable density across thelength of the cylindrical component.

Heating method: (1) Conventional heating, and (2) induction heating.Severity of quench: (1) Moderate quench (e.g., in oil), and (2) severe quench (e.g., in

water).

Subtask 1.2: Computer simulation of the heat treatment response of 8620 steelDante will be used to predict the heat treatment response, i.e., distortion, residual stress,

hardness, and microstructures evolution in a 8620 steel cylinder for combinations of thefollowing conditions:


Heating method: (1) Carburizing atmosphere in a conventional furnace, and (2) non-carburizing atmosphere in a conventional furnace.

Severity of quench: (1) Moderate quench (e.g., in oil), and (2) severe quench (e.g., inwater).

Subtask 1.3: Computer simulation of the heat treatment response of 601AB aluminum

alloyDante will be used to predict the heat treatment response, i.e., distortion, residual stress,

hardness, and microstructures evolution in an aluminum 601AB alloy cylinder forcombinations of the following conditions:


Heating method: (1) Conventional heating, and (2) induction heating.Severity of quench: (1) Moderate quench (e.g., in oil), and (2) severe quench (e.g., in

water).

7/28/2019 0301-4

5/7

TASK 2: Experiments and measurementsSoftware predictions obtained in Subtasks 1.1 1.3 will be verified by comparing them to

measurements of corresponding parameters for specimens obtained using processingconditions similar to those used in the simulations. The measurements are outlined in

Subtasks 2.1 to 2.3.

Subtask 2.1: Measurement of the heat treatment response of 5160 steelSoftware predictions for 5160 steel will be verified by comparing them to measurements

of corresponding parameters for 5160 steel specimens obtained using processingconditions similar to those used in the simulations.

Measurement of dimensional changes and distortion

A Starrett coordinate measuring machine will be used to measure the dimensionalchanges and distortion caused by the heat treatment process. Sufficient measurements

will be made to get accurate representation of the part before and after heat treatment.

Measurement of residual stressesThe standard x-ray diffraction method for measuring residual stress in metallic

components will be used. Line shifts due to a uniform strain in the component ismeasured and then the stress in the component is determined either by a calculation

involving the elastic constants of the material or by a calibration procedure involvingmeasurement of the strain produced by known stresses.

Measurement of volume fraction of metallurgical phases

Standard metallographic sample preparation techniques will be used to prepare specimensfrom the heat-treated cylinders. Samples will be prepared from three different cross-

sections of the cylinder that are equally spaced along the length of the cylinder. Opticaland scanning electron microscopy together with automated image analysis and energy

disperssive x-rays will be used to characterize and quantify the various phases in thespecimens.

Measurement of hardness

Standard Rockwell hardness and microhardness measurements will be performed on theheat-treated cylinders. Measurements will be performed across three different cross-

sections of the cylinder that are equally spaced along the length of the cylinder.

Subtask 2.2: Measurement of the heat treatment response of 8620 steelSoftware predictions for 8620 steel will be verified by comparing them to measurements

of corresponding parameters for 8620 steel specimens obtained using processingconditions similar to those used in the simulations.




7/28/2019 0301-4

6/7



involving the elastic constants of the material or by a calibration procedure involving

measurement of the strain produced by known stresses.





Measurement of hardness

Standard Rockwell hardness and microhardness measurements will be performed on theheat-treated cylinders. Measurements will be performed across three different cross-

sections of the cylinder that are equally spaced along the length of the cylinder.

Subtask 2.3: Measurement of the heat treatment response of 601AB aluminum alloySoftware predictions for 601AB aluminum alloy will be verified by comparing them to

measurements of corresponding parameters for 601AB aluminum alloy specimensobtained using processing conditions similar to those used in the simulations.






involving the elastic constants of the material or by a calibration procedure involvingmeasurement of the strain produced by known stresses.





7/28/2019 0301-4

7/7

Measurement of hardnessStandard Rockwell hardness and microhardness measurements will be performed on the

heat-treated cylinders. Measurements will be performed across three different cross-sections of the cylinder that are equally spaced along the length of the cylinder.

Deliverables

The main deliverable from the project will be a verified predictive strategy and software

that enable a complete assessment of the response of powder metallurgy components toheat treatment. The characteristics predicted by the software will include part distortion,

residual stresses, microstructure evolution, and hardness. An additional deliverable fromthe project will be documentation of the effect of processing conditions, including green

density, heating method, and severity of quench on the response of 5160 steel, 8620 steel,and 601AB aluminum alloy P/M parts to heat treatment.

Schedule

0301-4

Documents