Anisotropy of Mechanical Properties of. After Rolling and Hot Pressing

Transcription

1 Anisotropy of Mechanical Properties of Click Boron to Carbide edit Master Based Laminates title style After Rolling and Hot Pressing Nina Orlovskaya, Ryan VanderMeulen, PA Mykola Lugovy Institute for Problems of Materials Science, Kiev, Ukraine Sergey Yarmolenko, Jag Sankar North Carolina A&T State University, NC Financial Support: The European Commission INCO-Copernicus Grant ICA2-CT LAMINATES' The Army Center for Nanoscience and Nanomaterials, North Carolina A&T State University

2 Investigate the fracture toughness of B 4 C/B 4 C and B 4 C-ZrB 2 laminates by indentation technique Investigate the anisotropy of elastic properties of B 4 C/B 4 C laminates after rolling and hot pressing Determine the bending strength of the laminates in different planes (parallel and perpendicular to the hot pressing direction) Evaluate the crystallographic texture of material by XRD Objectives

3 Elastic Modulus Anisotropy of Boron Carbide Single Crystal Atomic structure of boron carbide Single crystal of boron carbide demonstrates strong anisotropy of elastic properties The orientation dependence of the Young s modulus of a single crystal of boron carbide

4 T0 ( ) dt M T M 1 RClick to edit Master text styles 2 If Design Concept of Laminates 2 1 E 1 ' te ' te 2 2 R2 R1 t t t t R2 0 Strain mismatch because of the CTEs difference R1 ' M E1 1 Residual compressive stress in a material with a lower CTE Residual tensile stress in a material with a higher CTE Residual tensile stress 1 Residual compressive stress Ho, S., Hillman, C., Lange, F.F., Suo, Z., Surface cracking in layers under biaxial compressive stress, J. Am. Ceram.Soc., 78, 9, , 1995.

5 Laminate Manufacturing Click to edit Master title style

6 Indentation of Samples Click to edit Master title style Indentation crack in plane A Plane A is parallel to hot pressing direction Plane B is perpendicular to hot pressing direction Plane C is parallel to hot pressing direction Indentation crack in plane C Top face Imprints Indentation crack in plane B The imprints were located on center line (a) or in the nodes of rectangular grid (b) Side face Hot pressing direction Side face a) b)

7 direction Indentation Cracks on Side Face of Laminate Crack perpendicular to layer and parallel to hot pressing Crack parallel to layer and perpendicular to hot pressing direction There is a strong anisotropy of crack sizes in different directions

8 Indentation Cracks on Side Face of Pure Click to Rolled edit Boron Master Carbide title style Crack parallel to hot pressing direction K 1c Fourth = level MPa m 1/2 Crack perpendicular to hot pressing direction K 1c = MPa m 1/2 Indentation cracks demonstrate weak anisotropy of fracture toughness in pure rolled boron carbide

9 Anisotropy of Pure Rolled Boron Carbide Elastic modulus GPa Strength MPa Specimens were loaded parallel and perpendicular to a green tape plane under four point bending The rolled boron carbide demonstrates different elastic modulus and strength for different loading directions Elastic modulus GPa Strength MPa

10 Anisotropy of Rolled B 4 C-30wt%SiC Elastic modulus GPa Strength MPa Specimens were loaded parallel and perpendicular to a green tape plane under four point bending The rolled B 4 C-30wt%SiC demonstrates weak anisotropy of elastic modulus and strength Elastic modulus GPa Strength MPa

11 Conclusions There is a strong anisotropy of crack sizes in different directions for boron carbide based laminates with alternated layers of different compositions. Indentation cracks demonstrate weak anisotropy of fracture toughness in pure rolled boron carbide. The rolled boron carbide demonstrates different elastic modulus and strength for different loading directions. The rolled B 4 C-30wt%SiC elastic modulus and strength. demonstrates weak anisotropy of XRD method does not show the crystallographic texture of boron carbide based laminates after rolling and hot pressing.