General Microstructures and Materials Properties in AM

Question 1

Define an Alloy (Legering) and a Phase (Fas = Enhetlig kemisk sammansättning)

Answer 1

Alloy: A mixture of chemical elements that can exist as one or more phases.

Phase: A physically distinct portion of a system with homogeneous composition and properties.

Question 2

What does Bragg’s Law ($n\lambda = 2d \sin \theta$) relate in X-ray diffraction?

Answer 2

It relates the wavelength of the X-ray ($\lambda$) to the atomic spacing ($d$) and the angle of incidence ($\theta$), allowing researchers to identify crystal structures.

Question 3

Describe the microstructure and properties of Martensite in steels.
(Martensit en av de viktigaste men också mest utmanande mikrostrukturerna. I 3D-printing med laser (SLM/PBF) bildas martensit nästan alltid naturligt)

Answer 3

Martensite is a highly strained, supersaturated carbon structure formed by rapid cooling (quenching). It is highly resistant to deformation (very hard) but can be brittle.

Question 4

What are the two main phases in Cemented Carbides (hårdmetall) and what properties do they provide?

Answer 4

WC (Tungsten Carbide): The hard phase; provides hardness and wear resistance.

Cobalt (Co): The binder/soft phase; provides toughness and ductility.

Question 5

Why is Carbon content control crucial in cemented carbides? (kolhaltkontroll) Low? High?

Answer 5

Low carbon: Forms the brittle $\eta$-phase, which decreases toughness.

High carbon: Causes graphite to precipitate, lowering mechanical properties.

Question 6

What defines the “Hierarchical Microstructure” often seen in AM metals?

Answer 6

A combination of solidification structures (columnar grains) and post-solidification structures (dislocation cells and nanoprecipitates) caused by repeated thermal cycling.

1. Makroskala - lager
2. Meso - melt pools
3. Mikro - grains
4. sub-mikro - cellular substructures

Question 7

How does Porosity specifically affect the mechanical performance of AM Ti-6Al-4V?

Answer 7

It significantly degrades fatigue properties and hardness by acting as initiation sites for cracks and reducing the overall density of the material.
(starkt men segt -> sprödhet, mindre material
sprickor i porer)

Question 8

What is the orimary challenge when applying stress constraints i topology optimazation?

Answer 8

Stress constrints introduce non-linearity